[*] Migrate to jspecify annotations

buildSrc/src/main/kotlin/de.siphalor.tweed5.base-module.gradle.kts

@@ -35,7 +35,10 @@ dependencies {
     testCompileOnly(libs.autoservice.annotations)
     testAnnotationProcessor(libs.autoservice.processor)
 
-    implementation(libs.jetbrains.annotations)
+    compileOnly(libs.jetbrains.annotations)
+    testImplementation(libs.jetbrains.annotations)
+    compileOnly(libs.jspecify.annotations)
+    testImplementation(libs.jspecify.annotations)
 
     implementation(libs.slf4j.api)
     "localRuntimeOnly"(libs.slf4j.rt)

gradle/libs.versions.toml

@@ -4,6 +4,7 @@ asm = "9.7"
 autoservice = "1.1.1"
 java = "8"
 jetbrains-annotations = "26.0.1"
+jspecify = "1.0.0"
 junit = "5.12.0"
 lombok = "1.18.34"
 mockito = "5.14.2"
@@ -19,6 +20,7 @@ asm-core = { group = "org.ow2.asm", name = "asm", version.ref = "asm" }
 autoservice-annotations = { group = "com.google.auto.service", name = "auto-service-annotations", version.ref = "autoservice" }
 autoservice-processor = { group = "com.google.auto.service", name = "auto-service", version.ref = "autoservice" }
 jetbrains-annotations = { group = "org.jetbrains", name = "annotations", version.ref = "jetbrains-annotations" }
+jspecify-annotations = { group = "org.jspecify", name = "jspecify", version.ref = "jspecify" }
 junit-platform = { group = "org.junit", name = "junit-bom", version.ref = "junit" }
 junit-core = { group = "org.junit.jupiter", name = "junit-jupiter" }
 junit-launcher = { group = "org.junit.platform", name = "junit-platform-launcher" }

tweed5-construct/src/main/java/de/siphalor/tweed5/construct/api/TweedConstructFactory.java

@@ -3,8 +3,7 @@ package de.siphalor.tweed5.construct.api;
 import de.siphalor.tweed5.construct.impl.TweedConstructFactoryImpl;
 import org.jetbrains.annotations.CheckReturnValue;
 import org.jetbrains.annotations.Contract;
-import org.jetbrains.annotations.NotNull;
+import org.jspecify.annotations.Nullable;
-import org.jetbrains.annotations.Nullable;
 
 /**
  * A factory that allows to construct instances of subclasses of a specific type.
@@ -20,7 +19,7 @@ public interface TweedConstructFactory<T> {
 	/**
 	 * Starts building a new factory for the given base class.
 	 */
-	static <T> TweedConstructFactory.@NotNull FactoryBuilder<T> builder(Class<T> baseClass) {
+	static <T> TweedConstructFactory.FactoryBuilder<T> builder(Class<T> baseClass) {
 		return TweedConstructFactoryImpl.builder(baseClass);
 	}
 
@@ -30,7 +29,7 @@ public interface TweedConstructFactory<T> {
 	 */
 	@CheckReturnValue
 	@Contract(pure = true)
-	<C extends T> @NotNull Construct<C> construct(@NotNull Class<C> subClass);
+	<C extends T> Construct<C> construct(Class<C> subClass);
 
 	/**
 	 * Builder for the factory.
@@ -40,19 +39,19 @@ public interface TweedConstructFactory<T> {
 		 * Defines a new typed argument of the given type.
 		 */
 		@Contract(mutates = "this", value = "_ -> this")
-		<A> @NotNull FactoryBuilder<T> typedArg(@NotNull Class<A> argType);
+		<A> FactoryBuilder<T> typedArg(Class<A> argType);
 
 		/**
 		 * Defines a new named argument with the given name and value type.
 		 */
 		@Contract(mutates = "this", value = "_, _ -> this")
-		<A> @NotNull FactoryBuilder<T> namedArg(@NotNull String name, @NotNull Class<A> argType);
+		<A> FactoryBuilder<T> namedArg(String name, Class<A> argType);
 
 		/**
 		 * Builds the factory.
 		 */
 		@Contract(pure = true)
-		@NotNull TweedConstructFactory<T> build();
+		TweedConstructFactory<T> build();
 	}
 
 	/**
@@ -71,7 +70,7 @@ public interface TweedConstructFactory<T> {
 		 * @see #namedArg(String, Object)
 		 */
 		@Contract(mutates = "this", value = "_ -> this")
-		<A> @NotNull Construct<C> typedArg(@NotNull A value);
+		<A> Construct<C> typedArg(A value);
 
 		/**
 		 * Binds a value to a typed argument of the given type.
@@ -81,19 +80,19 @@ public interface TweedConstructFactory<T> {
 		 * @see #namedArg(String, Object)
 		 */
 		@Contract(mutates = "this", value = "_, _ -> this")
-		<A> @NotNull Construct<C> typedArg(@NotNull Class<? super A> argType, @Nullable A value);
+		<A> Construct<C> typedArg(Class<? super A> argType, @Nullable A value);
 
 		/**
 		 * Binds a value to a named argument.
 		 * @see #typedArg(Object)
 		 */
 		@Contract(mutates = "this", value = "_, _ -> this")
-		<A> @NotNull Construct<C> namedArg(@NotNull String name, @Nullable A value);
+		<A> Construct<C> namedArg(String name, @Nullable A value);
 
 		/**
 		 * Finishes the binding and actually constructs the class.
 		 */
 		@Contract(pure = true)
-		@NotNull C finish();
+		C finish();
 	}
 }

tweed5-construct/src/main/java/de/siphalor/tweed5/construct/api/package-info.java

@@ -0,0 +1,4 @@
+@NullMarked
+package de.siphalor.tweed5.construct.api;
+
+import org.jspecify.annotations.NullMarked;

tweed5-construct/src/main/java/de/siphalor/tweed5/construct/impl/TweedConstructFactoryImpl.java

@@ -4,8 +4,7 @@ import de.siphalor.tweed5.construct.api.ConstructParameter;
 import de.siphalor.tweed5.construct.api.TweedConstruct;
 import de.siphalor.tweed5.construct.api.TweedConstructFactory;
 import lombok.*;
-import org.jetbrains.annotations.NotNull;
+import org.jspecify.annotations.Nullable;
-import org.jetbrains.annotations.Nullable;
 
 import java.lang.invoke.MethodHandle;
 import java.lang.invoke.MethodHandles;
@@ -37,11 +36,11 @@ public class TweedConstructFactoryImpl<T> implements TweedConstructFactory<T> {
 	}
 
 	@Override
-	public <C extends T> TweedConstructFactory.@NotNull Construct<C> construct(@NotNull Class<C> subClass) {
+	public <C extends T> TweedConstructFactory.Construct<C> construct(Class<C> subClass) {
 		return new Construct<>(getConstructTarget(subClass));
 	}
 
-	private <C extends T> @NotNull ConstructTarget<C> getConstructTarget(Class<C> type) {
+	private <C extends T> ConstructTarget<C> getConstructTarget(Class<C> type) {
 		ConstructTarget<C> cachedConstructTarget = readConstructTargetFromCache(type);
 		if (cachedConstructTarget != null) {
 			return cachedConstructTarget;
@@ -164,7 +163,7 @@ public class TweedConstructFactoryImpl<T> implements TweedConstructFactory<T> {
 		return new ConstructTarget<>(type, argOrder, createInvokerFromCandidate(type, executable));
 	}
 
-	private <C> Function<Object[], C> createInvokerFromCandidate(Class<C> type, Executable executable) {
+	private <C> Function<@Nullable Object[], C> createInvokerFromCandidate(Class<C> type, Executable executable) {
 		MethodHandle handle;
 		try {
 			if (executable instanceof Method) {
@@ -263,7 +262,7 @@ public class TweedConstructFactoryImpl<T> implements TweedConstructFactory<T> {
 		private final Map<String, Class<?>> namedArgs = new HashMap<>();
 
 		@Override
-		public <A> TweedConstructFactory.@NotNull FactoryBuilder<T> typedArg(@NotNull Class<A> argType) {
+		public <A> TweedConstructFactory.FactoryBuilder<T> typedArg(Class<A> argType) {
 			argType = boxClass(argType);
 			if (typedArgs.contains(argType)) {
 				throw new IllegalArgumentException("Argument for type " + argType + " has already been registered");
@@ -273,10 +272,7 @@ public class TweedConstructFactoryImpl<T> implements TweedConstructFactory<T> {
 		}
 
 		@Override
-		public <A> TweedConstructFactory.@NotNull FactoryBuilder<T> namedArg(
+		public <A> TweedConstructFactory.FactoryBuilder<T> namedArg(String name, Class<A> argType) {
-				@NotNull String name,
-				@NotNull Class<A> argType
-		) {
 			Class<?> existingArgType = namedArgs.get(name);
 			if (existingArgType != null) {
 				throw new IllegalArgumentException(
@@ -290,7 +286,7 @@ public class TweedConstructFactoryImpl<T> implements TweedConstructFactory<T> {
 		}
 
 		@Override
-		public @NotNull TweedConstructFactory<T> build() {
+		public TweedConstructFactory<T> build() {
 			return new TweedConstructFactoryImpl<>(
 					constructBaseClass,
 					typedArgs,
@@ -302,18 +298,18 @@ public class TweedConstructFactoryImpl<T> implements TweedConstructFactory<T> {
 	@RequiredArgsConstructor
 	private class Construct<C> implements TweedConstructFactory.Construct<C> {
 		private final ConstructTarget<C> target;
-		private final Map<Class<?>, Object> typedArgValues = new HashMap<>();
+		private final Map<Class<?>, @Nullable Object> typedArgValues = new HashMap<>();
-		private final Map<String, Object> namedArgValues = new HashMap<>();
+		private final Map<String, @Nullable Object> namedArgValues = new HashMap<>();
 
 		@Override
-		public <A> TweedConstructFactory.@NotNull Construct<C> typedArg(@NotNull A value) {
+		public <A> TweedConstructFactory.Construct<C> typedArg(A value) {
 			requireTypedArgExists(value.getClass(), value);
 			typedArgValues.put(value.getClass(), value);
 			return this;
 		}
 
 		@Override
-		public <A> TweedConstructFactory.@NotNull Construct<C> typedArg(@NotNull Class<? super A> argType, @Nullable A value) {
+		public <A> TweedConstructFactory.Construct<C> typedArg(Class<? super A> argType, @Nullable A value) {
 			argType = boxClass(argType);
 			if (value != null && !argType.isAssignableFrom(value.getClass())) {
 				throw new IllegalArgumentException(
@@ -327,7 +323,7 @@ public class TweedConstructFactoryImpl<T> implements TweedConstructFactory<T> {
 			return this;
 		}
 
-		private <A> void requireTypedArgExists(@NotNull Class<?> type, @Nullable A value) {
+		private <A> void requireTypedArgExists(Class<?> type, @Nullable A value) {
 			if (!typedArgs.contains(type)) {
 				throw new IllegalArgumentException(
 						"Typed argument for type " + type.getName() + " does not exist, value: " + value
@@ -336,7 +332,7 @@ public class TweedConstructFactoryImpl<T> implements TweedConstructFactory<T> {
 		}
 
 		@Override
-		public <A> TweedConstructFactory.@NotNull Construct<C> namedArg(@NotNull String name, @Nullable A value) {
+		public <A> TweedConstructFactory.Construct<C> namedArg(String name, @Nullable A value) {
 			Class<?> argType = namedArgs.get(name);
 			if (argType == null) {
 				throw new IllegalArgumentException(
@@ -353,10 +349,10 @@ public class TweedConstructFactoryImpl<T> implements TweedConstructFactory<T> {
 		}
 
 		@Override
-		public @NotNull C finish() {
+		public C finish() {
 			checkAllArgsFilled();
 
-			Object[] argValues = new Object[target.argOrder.length];
+			@Nullable Object[] argValues = new Object[target.argOrder.length];
 			for (int i = 0; i < target.argOrder.length; i++) {
 				Object arg = target.argOrder[i];
 				if (arg instanceof Class<?>) {
@@ -459,6 +455,6 @@ public class TweedConstructFactoryImpl<T> implements TweedConstructFactory<T> {
 	private static class ConstructTarget<C> {
 		Class<?> type;
 		Object[] argOrder;
-		Function<Object[], C> invoker;
+		Function<@Nullable Object[], C> invoker;
 	}
 }

tweed5-construct/src/main/java/de/siphalor/tweed5/construct/impl/package-info.java

@@ -1,4 +1,6 @@
 @ApiStatus.Internal
+@NullMarked
 package de.siphalor.tweed5.construct.impl;
 
 import org.jetbrains.annotations.ApiStatus;
+import org.jspecify.annotations.NullMarked;

tweed5-core/src/main/java/de/siphalor/tweed5/core/api/container/ConfigContainer.java

@@ -5,7 +5,7 @@ import de.siphalor.tweed5.core.api.extension.EntryExtensionsData;
 import de.siphalor.tweed5.core.api.entry.ConfigEntry;
 import de.siphalor.tweed5.core.api.extension.RegisteredExtensionData;
 import de.siphalor.tweed5.core.api.extension.TweedExtension;
-import org.jetbrains.annotations.Nullable;
+import org.jspecify.annotations.Nullable;
 
 import java.util.Collection;
 import java.util.Map;

tweed5-core/src/main/java/de/siphalor/tweed5/core/api/entry/BaseConfigEntry.java

@@ -4,13 +4,11 @@ import de.siphalor.tweed5.core.api.container.ConfigContainer;
 import de.siphalor.tweed5.core.api.extension.EntryExtensionsData;
 import lombok.Getter;
 import lombok.RequiredArgsConstructor;
-import org.jetbrains.annotations.NotNull;
 
 @RequiredArgsConstructor
 @Getter
 public abstract class BaseConfigEntry<T> implements ConfigEntry<T> {
 
-	@NotNull
 	private final Class<T> valueClass;
 	private ConfigContainer<?> container;
 	private EntryExtensionsData extensionsData;

tweed5-core/src/main/java/de/siphalor/tweed5/core/api/entry/ConfigEntry.java

@@ -2,7 +2,6 @@ package de.siphalor.tweed5.core.api.entry;
 
 import de.siphalor.tweed5.core.api.extension.EntryExtensionsData;
 import de.siphalor.tweed5.core.api.container.ConfigContainer;
-import org.jetbrains.annotations.NotNull;
 
 public interface ConfigEntry<T> {
 	Class<T> valueClass();
@@ -15,6 +14,5 @@ public interface ConfigEntry<T> {
 	void visitInOrder(ConfigEntryVisitor visitor);
 	void visitInOrder(ConfigEntryValueVisitor visitor, T value);
 
-	@NotNull
+	T deepCopy(T value);
-	T deepCopy(@NotNull T value);
 }

tweed5-core/src/main/java/de/siphalor/tweed5/core/api/package-info.java

@@ -0,0 +1,4 @@
+@NullMarked
+package de.siphalor.tweed5.core.api;
+
+import org.jspecify.annotations.NullMarked;

tweed5-core/src/main/java/de/siphalor/tweed5/core/impl/DefaultConfigContainer.java

@@ -12,11 +12,13 @@ import de.siphalor.tweed5.patchwork.impl.PatchworkClassPart;
 import de.siphalor.tweed5.utils.api.collection.InheritanceMap;
 import lombok.Getter;
 import lombok.Setter;
-import org.jetbrains.annotations.Nullable;
+import org.jspecify.annotations.NullUnmarked;
+import org.jspecify.annotations.Nullable;
 
 import java.lang.invoke.MethodHandle;
 import java.util.*;
 
+@NullUnmarked
 public class DefaultConfigContainer<T> implements ConfigContainer<T> {
 	@Getter
 	private ConfigContainerSetupPhase setupPhase = ConfigContainerSetupPhase.EXTENSIONS_SETUP;

tweed5-core/src/main/java/de/siphalor/tweed5/core/impl/entry/CollectionConfigEntryImpl.java

@@ -1,7 +1,6 @@
 package de.siphalor.tweed5.core.impl.entry;
 
 import de.siphalor.tweed5.core.api.entry.*;
-import org.jetbrains.annotations.NotNull;
 
 import java.util.Collection;
 import java.util.function.IntFunction;
@@ -52,7 +51,7 @@ public class CollectionConfigEntryImpl<E, T extends Collection<E>> extends BaseC
 	}
 
 	@Override
-	public @NotNull T deepCopy(@NotNull T value) {
+	public T deepCopy(T value) {
 		T copy = collectionConstructor.apply(value.size());
 		for (E element : value) {
 			copy.add(elementEntry().deepCopy(element));

tweed5-core/src/main/java/de/siphalor/tweed5/core/impl/entry/SimpleConfigEntryImpl.java

@@ -4,7 +4,6 @@ import de.siphalor.tweed5.core.api.entry.BaseConfigEntry;
 import de.siphalor.tweed5.core.api.entry.ConfigEntryValueVisitor;
 import de.siphalor.tweed5.core.api.entry.ConfigEntryVisitor;
 import de.siphalor.tweed5.core.api.entry.SimpleConfigEntry;
-import org.jetbrains.annotations.NotNull;
 
 public class SimpleConfigEntryImpl<T> extends BaseConfigEntry<T> implements SimpleConfigEntry<T> {
 	public SimpleConfigEntryImpl(Class<T> valueClass) {
@@ -22,8 +21,7 @@ public class SimpleConfigEntryImpl<T> extends BaseConfigEntry<T> implements Simp
 	}
 
 	@Override
-	@NotNull
+	public T deepCopy(T value) {
-	public T deepCopy(@NotNull T value) {
 		return value;
 	}
 }

tweed5-core/src/main/java/de/siphalor/tweed5/core/impl/entry/StaticMapCompoundConfigEntryImpl.java

@@ -1,7 +1,6 @@
 package de.siphalor.tweed5.core.impl.entry;
 
 import de.siphalor.tweed5.core.api.entry.*;
-import org.jetbrains.annotations.NotNull;
 
 import java.util.LinkedHashMap;
 import java.util.Map;
@@ -11,7 +10,7 @@ public class StaticMapCompoundConfigEntryImpl<T extends Map<String, Object>> ext
 	private final IntFunction<T> mapConstructor;
 	private final Map<String, ConfigEntry<?>> compoundEntries = new LinkedHashMap<>();
 
-	public StaticMapCompoundConfigEntryImpl(@NotNull Class<T> valueClass, IntFunction<T> mapConstructor) {
+	public StaticMapCompoundConfigEntryImpl(Class<T> valueClass, IntFunction<T> mapConstructor) {
 		super(valueClass);
 		this.mapConstructor = mapConstructor;
 	}
@@ -80,7 +79,7 @@ public class StaticMapCompoundConfigEntryImpl<T extends Map<String, Object>> ext
 	}
 
 	@Override
-	public @NotNull T deepCopy(@NotNull T value) {
+	public T deepCopy(T value) {
 		T copy = instantiateCompoundValue();
 		value.forEach((String key, Object element) -> {
 			//noinspection unchecked

tweed5-core/src/main/java/de/siphalor/tweed5/core/impl/package-info.java

@@ -1 +1,4 @@
-package de.siphalor.tweed5.core.impl;
+@NullMarked
+package de.siphalor.tweed5.core.impl;
+
+import org.jspecify.annotations.NullMarked;

tweed5-default-extensions/src/main/java/de/siphalor/tweed5/defaultextensions/comment/api/CommentExtension.java

@@ -2,7 +2,7 @@ package de.siphalor.tweed5.defaultextensions.comment.api;
 
 import de.siphalor.tweed5.core.api.entry.ConfigEntry;
 import de.siphalor.tweed5.core.api.extension.TweedExtension;
-import org.jetbrains.annotations.Nullable;
+import org.jspecify.annotations.Nullable;
 
 public interface CommentExtension extends TweedExtension {
 	@Nullable String getFullComment(ConfigEntry<?> configEntry);

tweed5-default-extensions/src/main/java/de/siphalor/tweed5/defaultextensions/comment/api/package-info.java

@@ -0,0 +1,4 @@
+@NullMarked
+package de.siphalor.tweed5.defaultextensions.comment.api;
+
+import org.jspecify.annotations.NullMarked;

tweed5-default-extensions/src/main/java/de/siphalor/tweed5/defaultextensions/comment/impl/CommentExtensionImpl.java

@@ -13,9 +13,12 @@ import de.siphalor.tweed5.data.extension.api.extension.ReadWriteRelatedExtension
 import de.siphalor.tweed5.defaultextensions.comment.api.*;
 import lombok.Getter;
 import lombok.Value;
-import org.jetbrains.annotations.Nullable;
+import org.jspecify.annotations.NonNull;
+import org.jspecify.annotations.NullUnmarked;
+import org.jspecify.annotations.Nullable;
 
 @AutoService(CommentExtension.class)
+@NullUnmarked
 public class CommentExtensionImpl implements ReadWriteRelatedExtension, CommentExtension {
 	@Getter
 	private RegisteredExtensionData<EntryExtensionsData, InternalCommentEntryData> internalEntryDataExtension;
@@ -62,8 +65,7 @@ public class CommentExtensionImpl implements ReadWriteRelatedExtension, CommentE
 	}
 
 	@Override
-	@Nullable
+	public @Nullable String getFullComment(@NonNull ConfigEntry<?> configEntry) {
-	public String getFullComment(ConfigEntry<?> configEntry) {
 		String comment = ((InternalCommentEntryData) configEntry.extensionsData()).commentProducer().createComment(configEntry);
 		return comment.isEmpty() ? null : comment;
 	}

tweed5-default-extensions/src/main/java/de/siphalor/tweed5/defaultextensions/comment/impl/TweedEntryWriterCommentMiddleware.java

@@ -6,8 +6,8 @@ import de.siphalor.tweed5.core.api.middleware.Middleware;
 import de.siphalor.tweed5.data.extension.api.TweedEntryWriter;
 import de.siphalor.tweed5.dataapi.api.TweedDataVisitor;
 import lombok.RequiredArgsConstructor;
-import org.jetbrains.annotations.NotNull;
+import org.jspecify.annotations.NonNull;
-import org.jetbrains.annotations.Nullable;
+import org.jspecify.annotations.Nullable;
 
 class TweedEntryWriterCommentMiddleware implements Middleware<TweedEntryWriter<?, ?>> {
 	public static final TweedEntryWriterCommentMiddleware INSTANCE = new TweedEntryWriterCommentMiddleware();
@@ -20,8 +20,8 @@ class TweedEntryWriterCommentMiddleware implements Middleware<TweedEntryWriter<?
 	@Override
 	public TweedEntryWriter<?, ?> process(TweedEntryWriter<?, ?> inner) {
 		//noinspection unchecked
-		TweedEntryWriter<Object, ConfigEntry<Object>> innerCasted = (TweedEntryWriter<Object, ConfigEntry<Object>>) inner;
+		TweedEntryWriter<Object, ConfigEntry<Object>> innerCasted = (TweedEntryWriter<Object, @NonNull ConfigEntry<Object>>) inner;
-		return (TweedEntryWriter<Object, ConfigEntry<Object>>) (writer, value, entry, context) -> {
+		return (TweedEntryWriter<Object, @NonNull ConfigEntry<Object>>) (writer, value, entry, context) -> {
 			if (writer instanceof CompoundDataVisitor) {
 				// Comment is already written in front of the key by the CompoundDataWriter,
 				// so we don't have to write it here.
@@ -94,7 +94,7 @@ class TweedEntryWriterCommentMiddleware implements Middleware<TweedEntryWriter<?
 		}
 
 		@Override
-		public void visitString(@NotNull String value) {
+		public void visitString(String value) {
 			delegate.visitString(value);
 		}
 

tweed5-default-extensions/src/main/java/de/siphalor/tweed5/defaultextensions/comment/impl/package-info.java

@@ -1,4 +1,6 @@
 @ApiStatus.Internal
+@NullMarked
 package de.siphalor.tweed5.defaultextensions.comment.impl;
 
-import org.jetbrains.annotations.ApiStatus;
+import org.jetbrains.annotations.ApiStatus;
+import org.jspecify.annotations.NullMarked;

tweed5-default-extensions/src/main/java/de/siphalor/tweed5/defaultextensions/pather/api/PathTracking.java

@@ -1,5 +1,7 @@
 package de.siphalor.tweed5.defaultextensions.pather.api;
 
+import org.jspecify.annotations.Nullable;
+
 import java.util.ArrayDeque;
 import java.util.Deque;
 
@@ -9,7 +11,7 @@ public class PathTracking implements PatherData {
 	private final Deque<String> pathParts = new ArrayDeque<>(50);
 	private final Deque<Integer> listIndexes = new ArrayDeque<>(10);
 
-	public Context currentContext() {
+	public @Nullable Context currentContext() {
 		return contextStack.peek();
 	}
 

tweed5-default-extensions/src/main/java/de/siphalor/tweed5/defaultextensions/pather/api/PathTrackingDataVisitor.java

@@ -2,7 +2,6 @@ package de.siphalor.tweed5.defaultextensions.pather.api;
 
 import de.siphalor.tweed5.dataapi.api.TweedDataVisitor;
 import lombok.RequiredArgsConstructor;
-import org.jetbrains.annotations.NotNull;
 
 @RequiredArgsConstructor
 public class PathTrackingDataVisitor implements TweedDataVisitor {
@@ -58,7 +57,7 @@ public class PathTrackingDataVisitor implements TweedDataVisitor {
 	}
 
 	@Override
-	public void visitString(@NotNull String value) {
+	public void visitString(String value) {
 		delegate.visitString(value);
 		valueVisited();
 	}

tweed5-default-extensions/src/main/java/de/siphalor/tweed5/defaultextensions/pather/api/package-info.java

@@ -0,0 +1,4 @@
+@NullMarked
+package de.siphalor.tweed5.defaultextensions.pather.api;
+
+import org.jspecify.annotations.NullMarked;

tweed5-default-extensions/src/main/java/de/siphalor/tweed5/defaultextensions/pather/impl/PatherExtensionImpl.java

@@ -15,10 +15,13 @@ import de.siphalor.tweed5.defaultextensions.pather.api.PathTracking;
 import de.siphalor.tweed5.defaultextensions.pather.api.PathTrackingDataReader;
 import de.siphalor.tweed5.defaultextensions.pather.api.PathTrackingDataVisitor;
 import de.siphalor.tweed5.defaultextensions.pather.api.PatherExtension;
-import org.jetbrains.annotations.NotNull;
+import lombok.val;
-import org.jetbrains.annotations.Nullable;
+import org.jspecify.annotations.NonNull;
+import org.jspecify.annotations.NullUnmarked;
+import org.jspecify.annotations.Nullable;
 
 @AutoService(PatherExtension.class)
+@NullUnmarked
 public class PatherExtensionImpl implements PatherExtension, TweedExtension, ReadWriteRelatedExtension {
 	private static final String PATHER_ID = "pather";
 
@@ -39,7 +42,7 @@ public class PatherExtensionImpl implements PatherExtension, TweedExtension, Rea
 		entryWriterMiddleware = createEntryWriterMiddleware();
 	}
 
-	private @NotNull Middleware<TweedEntryReader<?, ?>> createEntryReaderMiddleware() {
+	private @NonNull Middleware<TweedEntryReader<?, ?>> createEntryReaderMiddleware() {
 		return new Middleware<TweedEntryReader<?, ?>>() {
 			@Override
 			public String id() {
@@ -49,7 +52,7 @@ public class PatherExtensionImpl implements PatherExtension, TweedExtension, Rea
 			@Override
 			public TweedEntryReader<?, ?> process(TweedEntryReader<?, ?> inner) {
 				//noinspection unchecked
-				TweedEntryReader<Object, ConfigEntry<Object>> castedInner = (TweedEntryReader<Object, ConfigEntry<Object>>) inner;
+				val castedInner = (TweedEntryReader<Object, @NonNull ConfigEntry<Object>>) inner;
 
 				return (TweedDataReader reader, ConfigEntry<Object> entry, TweedReadContext context) -> {
 					if (context.extensionsData().isPatchworkPartSet(PathTracking.class)) {
@@ -74,7 +77,7 @@ public class PatherExtensionImpl implements PatherExtension, TweedExtension, Rea
 			@Override
 			public TweedEntryWriter<?, ?> process(TweedEntryWriter<?, ?> inner) {
 				//noinspection unchecked
-				TweedEntryWriter<Object, ConfigEntry<Object>> castedInner = (TweedEntryWriter<Object, ConfigEntry<Object>>) inner;
+				val castedInner = (TweedEntryWriter<Object, @NonNull ConfigEntry<Object>>) inner;
 
 				return (TweedDataVisitor writer, Object value, ConfigEntry<Object> entry, TweedWriteContext context) -> {
 					if (context.extensionsData().isPatchworkPartSet(PathTracking.class)) {

tweed5-default-extensions/src/main/java/de/siphalor/tweed5/defaultextensions/pather/impl/package-info.java

@@ -0,0 +1,6 @@
+@ApiStatus.Internal
+@NullMarked
+package de.siphalor.tweed5.defaultextensions.pather.impl;
+
+import org.jetbrains.annotations.ApiStatus;
+import org.jspecify.annotations.NullMarked;

tweed5-default-extensions/src/main/java/de/siphalor/tweed5/defaultextensions/validation/api/ConfigEntryValidator.java

@@ -2,11 +2,10 @@ package de.siphalor.tweed5.defaultextensions.validation.api;
 
 import de.siphalor.tweed5.core.api.entry.ConfigEntry;
 import de.siphalor.tweed5.defaultextensions.validation.api.result.ValidationResult;
-import org.jetbrains.annotations.NotNull;
+import org.jspecify.annotations.Nullable;
 
 public interface ConfigEntryValidator {
-	<T> ValidationResult<T> validate(ConfigEntry<T> configEntry, T value);
+	<T extends @Nullable Object> ValidationResult<T> validate(ConfigEntry<T> configEntry, T value);
 
-	@NotNull
 	<T> String description(ConfigEntry<T> configEntry);
 }

tweed5-default-extensions/src/main/java/de/siphalor/tweed5/defaultextensions/validation/api/ValidationExtension.java

@@ -3,7 +3,8 @@ package de.siphalor.tweed5.defaultextensions.validation.api;
 import de.siphalor.tweed5.core.api.entry.ConfigEntry;
 import de.siphalor.tweed5.core.api.extension.TweedExtension;
 import de.siphalor.tweed5.defaultextensions.validation.api.result.ValidationIssues;
+import org.jspecify.annotations.Nullable;
 
 public interface ValidationExtension extends TweedExtension {
-	<T> ValidationIssues validate(ConfigEntry<T> entry, T value);
+	<T extends @Nullable Object> ValidationIssues validate(ConfigEntry<T> entry, T value);
 }

tweed5-default-extensions/src/main/java/de/siphalor/tweed5/defaultextensions/validation/api/package-info.java

@@ -0,0 +1,4 @@
+@NullMarked
+package de.siphalor.tweed5.defaultextensions.validation.api;
+
+import org.jspecify.annotations.NullMarked;

tweed5-default-extensions/src/main/java/de/siphalor/tweed5/defaultextensions/validation/api/result/ValidationResult.java

@@ -3,7 +3,6 @@ package de.siphalor.tweed5.defaultextensions.validation.api.result;
 import lombok.AccessLevel;
 import lombok.Getter;
 import lombok.RequiredArgsConstructor;
-import org.jetbrains.annotations.NotNull;
 
 import java.util.ArrayList;
 import java.util.Collection;
@@ -14,7 +13,6 @@ import java.util.function.Function;
 @RequiredArgsConstructor(access = AccessLevel.PRIVATE)
 public class ValidationResult<T> {
 	private final T value;
-	@NotNull
 	private final Collection<ValidationIssue> issues;
 	private final boolean hasError;
 
@@ -22,7 +20,7 @@ public class ValidationResult<T> {
 		return new ValidationResult<>(value, Collections.emptyList(), false);
 	}
 
-	public static <T> ValidationResult<T> withIssues(T value, @NotNull Collection<ValidationIssue> issues) {
+	public static <T> ValidationResult<T> withIssues(T value, Collection<ValidationIssue> issues) {
 		return new ValidationResult<>(value, issues, issuesContainError(issues));
 	}
 

tweed5-default-extensions/src/main/java/de/siphalor/tweed5/defaultextensions/validation/api/validators/NonNullValidator.java

@@ -5,13 +5,13 @@ import de.siphalor.tweed5.defaultextensions.validation.api.ConfigEntryValidator;
 import de.siphalor.tweed5.defaultextensions.validation.api.result.ValidationIssue;
 import de.siphalor.tweed5.defaultextensions.validation.api.result.ValidationIssueLevel;
 import de.siphalor.tweed5.defaultextensions.validation.api.result.ValidationResult;
-import org.jetbrains.annotations.NotNull;
+import org.jspecify.annotations.Nullable;
 
 import java.util.Collections;
 
 public class NonNullValidator implements ConfigEntryValidator {
 	@Override
-	public <T> ValidationResult<T> validate(ConfigEntry<T> configEntry, T value) {
+	public <T extends @Nullable Object> ValidationResult<T> validate(ConfigEntry<T> configEntry, T value) {
 		if (value == null) {
 			return ValidationResult.withIssues(null, Collections.singleton(
 					new ValidationIssue("Value must not be null", ValidationIssueLevel.ERROR)
@@ -21,7 +21,7 @@ public class NonNullValidator implements ConfigEntryValidator {
 	}
 
 	@Override
-	public @NotNull <T> String description(ConfigEntry<T> configEntry) {
+	public <T> String description(ConfigEntry<T> configEntry) {
 		return "Must be set (not null).";
 	}
 }

tweed5-default-extensions/src/main/java/de/siphalor/tweed5/defaultextensions/validation/api/validators/NumberRangeValidator.java

@@ -7,23 +7,20 @@ import de.siphalor.tweed5.defaultextensions.validation.api.result.ValidationIssu
 import de.siphalor.tweed5.defaultextensions.validation.api.result.ValidationResult;
 import lombok.AllArgsConstructor;
 import lombok.Value;
-import org.jetbrains.annotations.NotNull;
+import org.jspecify.annotations.NonNull;
-import org.jetbrains.annotations.Nullable;
+import org.jspecify.annotations.Nullable;
 
 import java.util.Collections;
 
 @Value
 @AllArgsConstructor
-public class NumberRangeValidator<N extends Number> implements ConfigEntryValidator {
+public class NumberRangeValidator<N extends @NonNull Number> implements ConfigEntryValidator {
-	@NotNull
 	Class<N> numberClass;
-	@Nullable
+	@Nullable N minimum;
-	N minimum;
+	@Nullable N maximum;
-	@Nullable
-	N maximum;
 
 	@Override
-	public <T> ValidationResult<T> validate(ConfigEntry<T> configEntry, T value) {
+	public <T extends @Nullable Object> ValidationResult<T> validate(ConfigEntry<T> configEntry, T value) {
 		if (!(value instanceof Number)) {
 			return ValidationResult.withIssues(value, Collections.singleton(
 					new ValidationIssue("Value must be numeric", ValidationIssueLevel.ERROR)
@@ -56,7 +53,7 @@ public class NumberRangeValidator<N extends Number> implements ConfigEntryValida
 		return ValidationResult.ok(value);
 	}
 
-	private int compare(@NotNull Number a, @NotNull Number b) {
+	private int compare(Number a, Number b) {
 		if (numberClass == Byte.class) {
 			return Byte.compare(a.byteValue(), b.byteValue());
 		} else if (numberClass == Short.class) {
@@ -73,7 +70,7 @@ public class NumberRangeValidator<N extends Number> implements ConfigEntryValida
 	}
 
 	@Override
-	public @NotNull <T> String description(ConfigEntry<T> configEntry) {
+	public <T> String description(ConfigEntry<T> configEntry) {
 		if (minimum == null) {
 			if (maximum == null) {
 				return "";

tweed5-default-extensions/src/main/java/de/siphalor/tweed5/defaultextensions/validation/api/validators/SimpleValidatorMiddleware.java

@@ -6,7 +6,7 @@ import de.siphalor.tweed5.defaultextensions.validation.api.ConfigEntryValidator;
 import de.siphalor.tweed5.defaultextensions.validation.api.result.ValidationResult;
 import lombok.AllArgsConstructor;
 import lombok.Getter;
-import org.jetbrains.annotations.NotNull;
+import org.jspecify.annotations.Nullable;
 
 @Getter
 @AllArgsConstructor
@@ -18,12 +18,12 @@ public class SimpleValidatorMiddleware implements Middleware<ConfigEntryValidato
 	public ConfigEntryValidator process(ConfigEntryValidator inner) {
 		return new ConfigEntryValidator() {
 			@Override
-			public <T> ValidationResult<T> validate(ConfigEntry<T> configEntry, T value) {
+			public <T extends @Nullable Object> ValidationResult<T> validate(ConfigEntry<T> configEntry, T value) {
 				return inner.validate(configEntry, value).andThen(v -> validator.validate(configEntry, v));
 			}
 
 			@Override
-			public @NotNull <T> String description(ConfigEntry<T> configEntry) {
+			public <T extends @Nullable Object> String description(ConfigEntry<T> configEntry) {
 				String description = validator.description(configEntry);
 				if (description.isEmpty()) {
 					return inner.description(configEntry);

tweed5-default-extensions/src/main/java/de/siphalor/tweed5/defaultextensions/validation/api/validators/package-info.java

@@ -0,0 +1,4 @@
+@NullMarked
+package de.siphalor.tweed5.defaultextensions.validation.api.validators;
+
+import org.jspecify.annotations.NullMarked;

tweed5-default-extensions/src/main/java/de/siphalor/tweed5/defaultextensions/validation/impl/ValidationExtensionImpl.java

@@ -35,11 +35,13 @@ import lombok.Getter;
 import lombok.RequiredArgsConstructor;
 import lombok.Value;
 import org.jetbrains.annotations.NotNull;
-import org.jetbrains.annotations.Nullable;
+import org.jspecify.annotations.NullUnmarked;
+import org.jspecify.annotations.Nullable;
 
 import java.util.*;
 
 @AutoService(ValidationExtension.class)
+@NullUnmarked
 public class ValidationExtensionImpl implements ReadWriteRelatedExtension, ValidationExtension, CommentModifyingExtension {
 	private static final ValidationResult<?> PRIMITIVE_IS_NULL_RESULT = ValidationResult.withIssues(
 			null,
@@ -47,7 +49,7 @@ public class ValidationExtensionImpl implements ReadWriteRelatedExtension, Valid
 	);
 	private static final ConfigEntryValidator PRIMITIVE_VALIDATOR = new ConfigEntryValidator() {
 		@Override
-		public <T> ValidationResult<T> validate(ConfigEntry<T> configEntry, T value) {
+		public <T> ValidationResult<T> validate(@NotNull ConfigEntry<T> configEntry, @Nullable T value) {
 			if (value == null) {
 				//noinspection unchecked
 				return (ValidationResult<T>) PRIMITIVE_IS_NULL_RESULT;
@@ -56,18 +58,18 @@ public class ValidationExtensionImpl implements ReadWriteRelatedExtension, Valid
 		}
 
 		@Override
-		public @NotNull <T> String description(ConfigEntry<T> configEntry) {
+		public <T> String description(@NotNull ConfigEntry<T> configEntry) {
 			return "Value must not be null.";
 		}
 	};
 	private static final ConfigEntryValidator NOOP_VALIDATOR = new ConfigEntryValidator() {
 		@Override
-		public <T> ValidationResult<T> validate(ConfigEntry<T> configEntry, T value) {
+		public <T> ValidationResult<T> validate(@NotNull ConfigEntry<T> configEntry, @Nullable T value) {
 			return ValidationResult.ok(value);
 		}
 
 		@Override
-		public @NotNull <T> String description(ConfigEntry<T> configEntry) {
+		public <T> String description(@NotNull ConfigEntry<T> configEntry) {
 			return "";
 		}
 	};
@@ -166,7 +168,7 @@ public class ValidationExtensionImpl implements ReadWriteRelatedExtension, Valid
 	}
 
 	@Override
-	public <T> ValidationIssues validate(ConfigEntry<T> entry, T value) {
+	public <T> ValidationIssues validate(@NotNull ConfigEntry<T> entry, @Nullable T value) {
 		PathTracking pathTracking = new PathTracking();
 		ValidatingConfigEntryVisitor validatingVisitor = new ValidatingConfigEntryVisitor(pathTracking);
 

tweed5-default-extensions/src/main/java/de/siphalor/tweed5/defaultextensions/validation/impl/package-info.java

@@ -0,0 +1,6 @@
+@ApiStatus.Internal
+@NullMarked
+package de.siphalor.tweed5.defaultextensions.validation.impl;
+
+import org.jetbrains.annotations.ApiStatus;
+import org.jspecify.annotations.NullMarked;

tweed5-default-extensions/src/main/java/de/siphalor/tweed5/defaultextensions/validationfallback/api/ValidationFallbackValue.java

@@ -1,5 +1,7 @@
 package de.siphalor.tweed5.defaultextensions.validationfallback.api;
 
+import org.jspecify.annotations.Nullable;
+
 public interface ValidationFallbackValue {
-	Object validationFallbackValue();
+	@Nullable Object validationFallbackValue();
 }

tweed5-default-extensions/src/main/java/de/siphalor/tweed5/defaultextensions/validationfallback/api/package-info.java

@@ -0,0 +1,4 @@
+@NullMarked
+package de.siphalor.tweed5.defaultextensions.validationfallback.api;
+
+import org.jspecify.annotations.NullMarked;

tweed5-default-extensions/src/main/java/de/siphalor/tweed5/defaultextensions/validationfallback/impl/ValidationFallbackExtensionImpl.java

@@ -11,7 +11,7 @@ import de.siphalor.tweed5.defaultextensions.validation.api.result.ValidationIssu
 import de.siphalor.tweed5.defaultextensions.validation.api.result.ValidationResult;
 import de.siphalor.tweed5.defaultextensions.validationfallback.api.ValidationFallbackExtension;
 import de.siphalor.tweed5.defaultextensions.validationfallback.api.ValidationFallbackValue;
-import org.jetbrains.annotations.NotNull;
+import org.jspecify.annotations.Nullable;
 
 import java.util.ArrayList;
 import java.util.Collections;
@@ -55,7 +55,7 @@ public class ValidationFallbackExtensionImpl implements ValidationFallbackExtens
 		public ConfigEntryValidator process(ConfigEntryValidator inner) {
 			return new ConfigEntryValidator() {
 				@Override
-				public <T> ValidationResult<T> validate(ConfigEntry<T> configEntry, T value) {
+				public <T extends @Nullable Object> ValidationResult<T> validate(ConfigEntry<T> configEntry, T value) {
 					ValidationResult<T> result = inner.validate(configEntry, value);
 					if (!result.hasError()) {
 						return result;
@@ -90,7 +90,7 @@ public class ValidationFallbackExtensionImpl implements ValidationFallbackExtens
 				}
 
 				@Override
-				public @NotNull <T> String description(ConfigEntry<T> configEntry) {
+				public <T> String description(ConfigEntry<T> configEntry) {
 					if (!configEntry.extensionsData().isPatchworkPartSet(ValidationFallbackValue.class)) {
 						return inner.description(configEntry);
 					}

tweed5-default-extensions/src/main/java/de/siphalor/tweed5/defaultextensions/validationfallback/impl/package-info.java

@@ -0,0 +1,6 @@
+@ApiStatus.Internal
+@NullMarked
+package de.siphalor.tweed5.defaultextensions.validationfallback.impl;
+
+import org.jetbrains.annotations.ApiStatus;
+import org.jspecify.annotations.NullMarked;

tweed5-naming-format/src/main/java/de/siphalor/tweed5/namingformat/api/package-info.java

@@ -0,0 +1,4 @@
+@NullMarked
+package de.siphalor.tweed5.namingformat.api;
+
+import org.jspecify.annotations.NullMarked;

tweed5-naming-format/src/main/java/de/siphalor/tweed5/namingformat/impl/package-info.java

@@ -1,5 +1,6 @@
 @ApiStatus.Internal
-
+@NullMarked
 package de.siphalor.tweed5.namingformat.impl;
 
-import org.jetbrains.annotations.ApiStatus;
+import org.jetbrains.annotations.ApiStatus;
+import org.jspecify.annotations.NullMarked;

tweed5-patchwork/src/main/java/de/siphalor/tweed5/patchwork/api/PatchworkClassCreator.java

@@ -4,7 +4,10 @@ import de.siphalor.tweed5.patchwork.impl.ByteArrayClassLoader;
 import de.siphalor.tweed5.patchwork.impl.PatchworkClass;
 import de.siphalor.tweed5.patchwork.impl.PatchworkClassGenerator;
 import de.siphalor.tweed5.patchwork.impl.PatchworkClassPart;
-import lombok.*;
+import lombok.AccessLevel;
+import lombok.NoArgsConstructor;
+import lombok.Setter;
+import lombok.Value;
 
 import java.lang.invoke.MethodHandle;
 import java.lang.invoke.MethodHandles;
@@ -16,17 +19,18 @@ import java.util.stream.Collectors;
 
 @Value
 public class PatchworkClassCreator<P extends Patchwork<P>> {
-	@NonNull
 	Class<P> patchworkInterface;
-	@NonNull
 	PatchworkClassGenerator.Config generatorConfig;
 
 	public static <P extends Patchwork<P>> Builder<P> builder() {
 		return new Builder<>();
 	}
 
-	public PatchworkClass<P> createClass(Collection<Class<?>> partInterfaces) throws PatchworkClassGenerator.GenerationException {
+	public PatchworkClass<P> createClass(Collection<Class<?>> partInterfaces) throws
-		List<PatchworkClassPart> parts = partInterfaces.stream().map(PatchworkClassPart::new).collect(Collectors.toList());
+			PatchworkClassGenerator.GenerationException {
+		List<PatchworkClassPart> parts = partInterfaces.stream()
+				.map(PatchworkClassPart::new)
+				.collect(Collectors.toList());
 
 		PatchworkClassGenerator generator = new PatchworkClassGenerator(generatorConfig, parts);
 		try {
@@ -45,7 +49,10 @@ public class PatchworkClassCreator<P extends Patchwork<P>> {
 				MethodHandle setterHandle = lookup.findSetter(patchworkClass, part.fieldName(), part.partInterface());
 				part.fieldSetter(setterHandle);
 			} catch (NoSuchFieldException | IllegalAccessException e) {
-				throw new IllegalStateException("Failed to access setter for patchwork part " + part.partInterface().getName(), e);
+				throw new IllegalStateException(
+						"Failed to access setter for patchwork part " + part.partInterface().getName(),
+						e
+				);
 			}
 		}
 		try {
@@ -67,9 +74,7 @@ public class PatchworkClassCreator<P extends Patchwork<P>> {
 	@Setter
 	@NoArgsConstructor(access = AccessLevel.PRIVATE)
 	public static class Builder<P extends Patchwork<P>> {
-		@NonNull
 		private Class<P> patchworkInterface;
-		@NonNull
 		private String classPackage;
 		private String classPrefix = "";
 

tweed5-patchwork/src/main/java/de/siphalor/tweed5/patchwork/api/package-info.java

@@ -0,0 +1,4 @@
+@NullMarked
+package de.siphalor.tweed5.patchwork.api;
+
+import org.jspecify.annotations.NullMarked;

tweed5-patchwork/src/main/java/de/siphalor/tweed5/patchwork/impl/ByteArrayClassLoader.java

@@ -1,8 +1,10 @@
 package de.siphalor.tweed5.patchwork.impl;
 
 
+import org.jspecify.annotations.Nullable;
+
 public class ByteArrayClassLoader extends ClassLoader {
-	public static Class<?> loadClass(String binaryClassName, byte[] byteCode) {
+	public static Class<?> loadClass(@Nullable String binaryClassName, byte[] byteCode) {
 		return new ByteArrayClassLoader(ByteArrayClassLoader.class.getClassLoader())
 				.createClass(binaryClassName, byteCode);
 	}
@@ -11,7 +13,7 @@ public class ByteArrayClassLoader extends ClassLoader {
 		super(parent);
 	}
 
-	public Class<?> createClass(String binaryClassName, byte[] byteCode) {
+	public Class<?> createClass(@Nullable String binaryClassName, byte[] byteCode) {
 		Class<?> clazz = defineClass(binaryClassName, byteCode, 0, byteCode.length);
 		resolveClass(clazz);
 		return clazz;

tweed5-patchwork/src/main/java/de/siphalor/tweed5/patchwork/impl/PatchworkClassGenerator.java

@@ -4,6 +4,8 @@ import de.siphalor.tweed5.patchwork.api.Patchwork;
 import de.siphalor.tweed5.patchwork.api.PatchworkPartIsNullException;
 import de.siphalor.tweed5.patchwork.impl.util.StreamUtils;
 import lombok.*;
+import org.jspecify.annotations.NonNull;
+import org.jspecify.annotations.Nullable;
 import org.objectweb.asm.*;
 import org.objectweb.asm.commons.GeneratorAdapter;
 
@@ -21,7 +23,8 @@ public class PatchworkClassGenerator {
 	 */
 	private static final int CLASS_VERSION = Opcodes.V1_8;
 	private static final String TARGET_PACKAGE = "de.siphalor.tweed5.core.generated.contextextensions";
-	private static final List<Type> DEFAULT_PATHWORK_INTERFACES = Collections.singletonList(Type.getType(Patchwork.class));
+	private static final List<Type> DEFAULT_PATHWORK_INTERFACES
+			= Collections.singletonList(Type.getType(Patchwork.class));
 
 	private static final String INNER_EQUALS_METHOD_NAME = "patchwork$innerEquals";
 
@@ -458,7 +461,13 @@ public class PatchworkClassGenerator {
 	}
 	// </editor-fold>
 
-	private GeneratorAdapter createMethod(int access, String name, String desc, String signature, String[] exceptions) {
+	private GeneratorAdapter createMethod(
+			int access,
+			String name,
+			String desc,
+			@Nullable String signature,
+			String @Nullable [] exceptions
+	) {
 		MethodVisitor methodVisitor = classWriter.visitMethod(access, name, desc, signature, exceptions);
 		return new GeneratorAdapter(methodVisitor, access, name, desc);
 	}
@@ -502,7 +511,13 @@ public class PatchworkClassGenerator {
 		}
 
 		@Override
-		public MethodVisitor visitMethod(int access, String name, String descriptor, String signature, String[] exceptions) {
+		public MethodVisitor visitMethod(
+				int access,
+				String name,
+				String descriptor,
+				String signature,
+				String[] exceptions
+		) {
 			GeneratorAdapter methodWriter = createMethod(Opcodes.ACC_PUBLIC, name, descriptor, signature, exceptions);
 			return new PartMethodVisitor(api, methodWriter, descriptor, extensionClass);
 		}
@@ -513,7 +528,12 @@ public class PatchworkClassGenerator {
 		private final String methodDescriptor;
 		private final PatchworkClassPart patchworkPart;
 
-		protected PartMethodVisitor(int api, GeneratorAdapter methodWriter, String methodDescriptor, PatchworkClassPart patchworkPart) {
+		protected PartMethodVisitor(
+				int api,
+				GeneratorAdapter methodWriter,
+				String methodDescriptor,
+				PatchworkClassPart patchworkPart
+		) {
 			super(api);
 			this.methodWriter = methodWriter;
 			this.patchworkPart = patchworkPart;
@@ -531,7 +551,12 @@ public class PatchworkClassGenerator {
 
 			methodWriter.visitCode();
 			methodWriter.visitVarInsn(Opcodes.ALOAD, 0);
-			methodWriter.visitFieldInsn(Opcodes.GETFIELD, internalClassName(), patchworkPart.fieldName(), Type.getDescriptor(patchworkPart.partInterface()));
+			methodWriter.visitFieldInsn(
+					Opcodes.GETFIELD,
+					internalClassName(),
+					patchworkPart.fieldName(),
+					Type.getDescriptor(patchworkPart.partInterface())
+			);
 			methodWriter.dup();
 			methodWriter.ifNull(nullLabel);
 			methodWriter.loadArgs();
@@ -563,11 +588,9 @@ public class PatchworkClassGenerator {
 
 	@Data
 	public static class Config {
-		@NonNull
+		@lombok.NonNull
-		private String classPackage;
+		private @NonNull String classPackage;
-		@NonNull
 		private String classPrefix = "";
-		@NonNull
 		private Collection<Class<?>> markerInterfaces = Collections.emptyList();
 	}
 
@@ -594,12 +617,16 @@ public class PatchworkClassGenerator {
 		transient Collection<Method> signatures;
 
 		private DuplicateMethodsException(Collection<Method> methods) {
-			super("Duplicate method signatures:\n" + methods.stream().map(DuplicateMethodsException::getMethodMessage).collect(Collectors.joining("\n")));
+			super("Duplicate method signatures:\n" + methods.stream()
+					.map(DuplicateMethodsException::getMethodMessage)
+					.collect(Collectors.joining("\n")));
 			this.signatures = methods;
 		}
 
 		private static String getMethodMessage(Method method) {
-			StringBuilder stringBuilder = new StringBuilder("\t- " + method.getDeclaringClass().getCanonicalName() + "#(");
+			StringBuilder stringBuilder = new StringBuilder("\t- "
+					+ method.getDeclaringClass().getCanonicalName()
+					+ "#(");
 			for (Class<?> parameterType : method.getParameterTypes()) {
 				stringBuilder.append(parameterType.getCanonicalName());
 				stringBuilder.append(", ");

tweed5-patchwork/src/main/java/de/siphalor/tweed5/patchwork/impl/package-info.java

@@ -0,0 +1,6 @@
+@ApiStatus.Internal
+@NullMarked
+package de.siphalor.tweed5.patchwork.impl;
+
+import org.jetbrains.annotations.ApiStatus;
+import org.jspecify.annotations.NullMarked;

tweed5-serde-api/src/main/java/de/siphalor/tweed5/dataapi/api/TweedDataReadException.java

@@ -3,7 +3,7 @@ package de.siphalor.tweed5.dataapi.api;
 import lombok.AccessLevel;
 import lombok.Getter;
 import lombok.Setter;
-import org.jetbrains.annotations.Nullable;
+import org.jspecify.annotations.Nullable;
 
 @Getter
 public class TweedDataReadException extends RuntimeException {
@@ -28,8 +28,7 @@ public class TweedDataReadException extends RuntimeException {
 		private String message;
 		private Throwable cause;
 		@Setter(AccessLevel.NONE)
-		@Nullable
+		private @Nullable TweedDataReaderRecoverMode recoverMode;
-		private TweedDataReaderRecoverMode recoverMode;
 
 		public TweedDataReadException build() {
 			return new TweedDataReadException(message, cause, recoverMode);

tweed5-serde-api/src/main/java/de/siphalor/tweed5/dataapi/api/TweedDataVisitor.java

@@ -1,7 +1,5 @@
 package de.siphalor.tweed5.dataapi.api;
 
-import org.jetbrains.annotations.NotNull;
-
 public interface TweedDataVisitor {
 	void visitNull();
 	void visitBoolean(boolean value);
@@ -11,7 +9,7 @@ public interface TweedDataVisitor {
 	void visitLong(long value);
 	void visitFloat(float value);
 	void visitDouble(double value);
-	void visitString(@NotNull String value);
+	void visitString(String value);
 
 	default void visitEmptyList() {
 		visitListStart();

tweed5-serde-api/src/main/java/de/siphalor/tweed5/dataapi/api/package-info.java

@@ -0,0 +1,4 @@
+@NullMarked
+package de.siphalor.tweed5.dataapi.api;
+
+import org.jspecify.annotations.NullMarked;

tweed5-serde-extension/src/main/java/de/siphalor/tweed5/data/extension/api/ReadWriteExtension.java

@@ -5,13 +5,23 @@ import de.siphalor.tweed5.core.api.extension.TweedExtension;
 import de.siphalor.tweed5.data.extension.api.extension.ReadWriteContextExtensionsData;
 import de.siphalor.tweed5.dataapi.api.TweedDataReader;
 import de.siphalor.tweed5.dataapi.api.TweedDataVisitor;
+import org.jspecify.annotations.Nullable;
 
 public interface ReadWriteExtension extends TweedExtension {
 	void setEntryReaderWriterDefinition(ConfigEntry<?> entry, EntryReaderWriterDefinition readerWriterDefinition);
 
 	ReadWriteContextExtensionsData createReadWriteContextExtensionsData();
 
-	<T> T read(TweedDataReader reader, ConfigEntry<T> entry, ReadWriteContextExtensionsData contextExtensionsData) throws TweedEntryReadException;
+	<T extends @Nullable Object> T read(
+			TweedDataReader reader,
+			ConfigEntry<T> entry,
+			ReadWriteContextExtensionsData contextExtensionsData
+	) throws TweedEntryReadException;
 
-	<T> void write(TweedDataVisitor writer, T value, ConfigEntry<T> entry, ReadWriteContextExtensionsData contextExtensionsData) throws TweedEntryWriteException;
+	<T extends @Nullable Object> void write(
+			TweedDataVisitor writer,
+			T value,
+			ConfigEntry<T> entry,
+			ReadWriteContextExtensionsData contextExtensionsData
+	) throws TweedEntryWriteException;
 }

tweed5-serde-extension/src/main/java/de/siphalor/tweed5/data/extension/api/TweedEntryReader.java

@@ -3,8 +3,11 @@ package de.siphalor.tweed5.data.extension.api;
 import de.siphalor.tweed5.core.api.entry.ConfigEntry;
 import de.siphalor.tweed5.dataapi.api.TweedDataReadException;
 import de.siphalor.tweed5.dataapi.api.TweedDataReader;
+import org.jspecify.annotations.Nullable;
 
 @FunctionalInterface
-public interface TweedEntryReader<T, C extends ConfigEntry<T>> {
+public interface TweedEntryReader<T extends @Nullable Object, C extends ConfigEntry<T>> {
-	T read(TweedDataReader reader, C entry, TweedReadContext context) throws TweedEntryReadException, TweedDataReadException;
+	T read(TweedDataReader reader, C entry, TweedReadContext context) throws
+			TweedEntryReadException,
+			TweedDataReadException;
 }

tweed5-serde-extension/src/main/java/de/siphalor/tweed5/data/extension/api/TweedEntryWriter.java

@@ -3,8 +3,9 @@ package de.siphalor.tweed5.data.extension.api;
 import de.siphalor.tweed5.core.api.entry.ConfigEntry;
 import de.siphalor.tweed5.dataapi.api.TweedDataWriteException;
 import de.siphalor.tweed5.dataapi.api.TweedDataVisitor;
+import org.jspecify.annotations.Nullable;
 
 @FunctionalInterface
-public interface TweedEntryWriter<T, C extends ConfigEntry<T>> {
+public interface TweedEntryWriter<T extends @Nullable Object, C extends ConfigEntry<T>> {
-	void write(TweedDataVisitor writer, T value, C entry, TweedWriteContext context) throws TweedEntryWriteException, TweedDataWriteException;
+	void write(TweedDataVisitor writer, @Nullable T value, C entry, TweedWriteContext context) throws TweedEntryWriteException, TweedDataWriteException;
 }

tweed5-serde-extension/src/main/java/de/siphalor/tweed5/data/extension/api/extension/ReadWriteRelatedExtension.java

@@ -3,7 +3,7 @@ package de.siphalor.tweed5.data.extension.api.extension;
 import de.siphalor.tweed5.core.api.middleware.Middleware;
 import de.siphalor.tweed5.data.extension.api.TweedEntryReader;
 import de.siphalor.tweed5.data.extension.api.TweedEntryWriter;
-import org.jetbrains.annotations.Nullable;
+import org.jspecify.annotations.Nullable;
 
 public interface ReadWriteRelatedExtension {
 	default void setupReadWriteExtension(ReadWriteExtensionSetupContext context) {

tweed5-serde-extension/src/main/java/de/siphalor/tweed5/data/extension/api/package-info.java

@@ -0,0 +1,4 @@
+@NullMarked
+package de.siphalor.tweed5.data.extension.api;
+
+import org.jspecify.annotations.NullMarked;

tweed5-serde-extension/src/main/java/de/siphalor/tweed5/data/extension/api/readwrite/TweedEntryReaderWriters.java

@@ -8,6 +8,7 @@ import de.siphalor.tweed5.data.extension.api.TweedEntryWriter;
 import de.siphalor.tweed5.data.extension.impl.TweedEntryReaderWriterImpls;
 import lombok.AccessLevel;
 import lombok.NoArgsConstructor;
+import org.jspecify.annotations.NonNull;
 
 import java.util.Collection;
 
@@ -55,11 +56,11 @@ public class TweedEntryReaderWriters {
 
 	public static <T, C extends Collection<T>> TweedEntryReaderWriter<C, CollectionConfigEntry<T, C>> collectionReaderWriter() {
 		//noinspection unchecked
-		return (TweedEntryReaderWriter<C, CollectionConfigEntry<T,C>>)(TweedEntryReaderWriter<?, ?>) TweedEntryReaderWriterImpls.COLLECTION_READER_WRITER;
+		return (TweedEntryReaderWriter<C, @NonNull CollectionConfigEntry<T, C>>) (TweedEntryReaderWriter<?, ?>) TweedEntryReaderWriterImpls.COLLECTION_READER_WRITER;
 	}
 
 	public static <T> TweedEntryReaderWriter<T, CompoundConfigEntry<T>> compoundReaderWriter() {
 		//noinspection unchecked
-		return (TweedEntryReaderWriter<T, CompoundConfigEntry<T>>)(TweedEntryReaderWriter<?, ?>) TweedEntryReaderWriterImpls.COMPOUND_READER_WRITER;
+		return (TweedEntryReaderWriter<T, @NonNull CompoundConfigEntry<T>>) (TweedEntryReaderWriter<?, ?>) TweedEntryReaderWriterImpls.COMPOUND_READER_WRITER;
 	}
 }

tweed5-serde-extension/src/main/java/de/siphalor/tweed5/data/extension/api/readwrite/package-info.java

@@ -0,0 +1,4 @@
+@NullMarked
+package de.siphalor.tweed5.data.extension.api.readwrite;
+
+import org.jspecify.annotations.NullMarked;

tweed5-serde-extension/src/main/java/de/siphalor/tweed5/data/extension/impl/ReadWriteExtensionImpl.java

@@ -22,6 +22,10 @@ import de.siphalor.tweed5.patchwork.impl.PatchworkClassGenerator;
 import de.siphalor.tweed5.patchwork.impl.PatchworkClassPart;
 import lombok.Setter;
 import lombok.Value;
+import lombok.val;
+import org.jspecify.annotations.NonNull;
+import org.jspecify.annotations.NullUnmarked;
+import org.jspecify.annotations.Nullable;
 
 import java.lang.invoke.MethodHandle;
 import java.util.Collection;
@@ -29,14 +33,16 @@ import java.util.HashMap;
 import java.util.Map;
 
 @AutoService(ReadWriteExtension.class)
+@NullUnmarked
 public class ReadWriteExtensionImpl implements ReadWriteExtension {
 
 	private RegisteredExtensionData<EntryExtensionsData, EntryReaderWriterDefinition> readerWriterDefinitionExtension;
 	private RegisteredExtensionData<EntryExtensionsData, ReadWriteEntryDataExtension> readWriteEntryDataExtension;
 	private DefaultMiddlewareContainer<TweedEntryReader<?, ?>> entryReaderMiddlewareContainer;
 	private DefaultMiddlewareContainer<TweedEntryWriter<?, ?>> entryWriterMiddlewareContainer;
-	private Map<Class<?>, RegisteredExtensionDataImpl<ReadWriteContextExtensionsData, ?>> readWriteContextExtensionsDataClasses;
+	private Map<Class<?>, RegisteredExtensionDataImpl<ReadWriteContextExtensionsData, ?>>
-	private PatchworkClass<ReadWriteContextExtensionsData> readWriteContextExtensionsDataPatchwork;
+			readWriteContextExtensionsDataClasses;
+	private PatchworkClass<@NonNull ReadWriteContextExtensionsData> readWriteContextExtensionsDataPatchwork;
 
 	@Override
 	public String getId() {
@@ -54,11 +60,17 @@ public class ReadWriteExtensionImpl implements ReadWriteExtension {
 
 		ReadWriteExtensionSetupContext setupContext = new ReadWriteExtensionSetupContext() {
 			@Override
-			public <E> RegisteredExtensionData<ReadWriteContextExtensionsData, E> registerReadWriteContextExtensionData(Class<E> extensionDataClass) {
+			public <E> RegisteredExtensionData<ReadWriteContextExtensionsData, E> registerReadWriteContextExtensionData(
+					Class<E> extensionDataClass
+			) {
 				if (readWriteContextExtensionsDataClasses.containsKey(extensionDataClass)) {
-					throw new IllegalArgumentException("Context extension " + extensionDataClass.getName() + " is already registered");
+					throw new IllegalArgumentException("Context extension "
+							+ extensionDataClass.getName()
+							+ " is already registered");
 				}
-				RegisteredExtensionDataImpl<ReadWriteContextExtensionsData, E> registeredExtensionData = new RegisteredExtensionDataImpl<>();
+				RegisteredExtensionDataImpl<ReadWriteContextExtensionsData, E>
+						registeredExtensionData
+						= new RegisteredExtensionDataImpl<>();
 				readWriteContextExtensionsDataClasses.put(extensionDataClass, registeredExtensionData);
 				return registeredExtensionData;
 			}
@@ -73,11 +85,13 @@ public class ReadWriteExtensionImpl implements ReadWriteExtension {
 
 				rwExtension.setupReadWriteExtension(setupContext);
 
-				if (rwExtension.entryReaderMiddleware() != null) {
+				val readerMiddleware = rwExtension.entryReaderMiddleware();
-					entryReaderMiddlewareContainer.register(rwExtension.entryReaderMiddleware());
+				if (readerMiddleware != null) {
+					entryReaderMiddlewareContainer.register(readerMiddleware);
 				}
-				if (rwExtension.entryWriterMiddleware() != null) {
+				val writerMiddleware = rwExtension.entryWriterMiddleware();
-					entryWriterMiddlewareContainer.register(rwExtension.entryWriterMiddleware());
+				if (writerMiddleware != null) {
+					entryWriterMiddlewareContainer.register(writerMiddleware);
 				}
 			}
 		}
@@ -85,20 +99,26 @@ public class ReadWriteExtensionImpl implements ReadWriteExtension {
 		entryReaderMiddlewareContainer.seal();
 		entryWriterMiddlewareContainer.seal();
 
-		PatchworkClassCreator<ReadWriteContextExtensionsData> patchworkClassCreator = PatchworkClassCreator.<ReadWriteContextExtensionsData>builder()
+		val patchworkClassCreator = PatchworkClassCreator.<ReadWriteContextExtensionsData>builder()
 				.patchworkInterface(ReadWriteContextExtensionsData.class)
 				.classPackage("de.siphalor.tweed5.data.extension.generated")
 				.classPrefix("ReadWriteContextExtensionsData$")
 				.build();
 
 		try {
-			readWriteContextExtensionsDataPatchwork = patchworkClassCreator.createClass(readWriteContextExtensionsDataClasses.keySet());
+			readWriteContextExtensionsDataPatchwork =
+					patchworkClassCreator.createClass(readWriteContextExtensionsDataClasses.keySet());
 			for (PatchworkClassPart patchworkClassPart : readWriteContextExtensionsDataPatchwork.parts()) {
-				RegisteredExtensionDataImpl<ReadWriteContextExtensionsData, ?> registeredExtension = readWriteContextExtensionsDataClasses.get(patchworkClassPart.partInterface());
+				RegisteredExtensionDataImpl<ReadWriteContextExtensionsData, ?>
+						registeredExtension
+						= readWriteContextExtensionsDataClasses.get(patchworkClassPart.partInterface());
 				registeredExtension.setter = patchworkClassPart.fieldSetter();
 			}
 		} catch (PatchworkClassGenerator.GenerationException e) {
-			throw new IllegalStateException("Failed to generate read write context extensions' data patchwork class", e);
+			throw new IllegalStateException(
+					"Failed to generate read write context extensions' data patchwork class",
+					e
+			);
 		}
 	}
 
@@ -115,14 +135,19 @@ public class ReadWriteExtensionImpl implements ReadWriteExtension {
 			baseWriter = TweedEntryReaderWriterImpls.NOOP_READER_WRITER;
 		}
 
-		readWriteEntryDataExtension.set(configEntry.extensionsData(), new ReadWriteEntryDataExtensionImpl(
+		readWriteEntryDataExtension.set(
-				entryReaderMiddlewareContainer.process(baseReader),
+				configEntry.extensionsData(), new ReadWriteEntryDataExtensionImpl(
-				entryWriterMiddlewareContainer.process(baseWriter)
+						entryReaderMiddlewareContainer.process(baseReader),
-		));
+						entryWriterMiddlewareContainer.process(baseWriter)
+				)
+		);
 	}
 
 	@Override
-	public void setEntryReaderWriterDefinition(ConfigEntry<?> entry, EntryReaderWriterDefinition readerWriterDefinition) {
+	public void setEntryReaderWriterDefinition(
+			@NonNull ConfigEntry<?> entry,
+			@NonNull EntryReaderWriterDefinition readerWriterDefinition
+	) {
 		readerWriterDefinitionExtension.set(entry.extensionsData(), readerWriterDefinition);
 	}
 
@@ -136,7 +161,11 @@ public class ReadWriteExtensionImpl implements ReadWriteExtension {
 	}
 
 	@Override
-	public <T> T read(TweedDataReader reader, ConfigEntry<T> entry, ReadWriteContextExtensionsData contextExtensionsData) throws TweedEntryReadException {
+	public <T> T read(
+			@NonNull TweedDataReader reader,
+			@NonNull ConfigEntry<T> entry,
+			@NonNull ReadWriteContextExtensionsData contextExtensionsData
+	) throws TweedEntryReadException {
 		try {
 			return getReaderChain(entry).read(reader, entry, new TweedReadWriteContextImpl(contextExtensionsData));
 		} catch (TweedDataReadException e) {
@@ -145,7 +174,12 @@ public class ReadWriteExtensionImpl implements ReadWriteExtension {
 	}
 
 	@Override
-	public <T> void write(TweedDataVisitor writer, T value, ConfigEntry<T> entry, ReadWriteContextExtensionsData contextExtensionsData) throws TweedEntryWriteException {
+	public <T> void write(
+			@NonNull TweedDataVisitor writer,
+			@Nullable T value,
+			@NonNull ConfigEntry<T> entry,
+			@NonNull ReadWriteContextExtensionsData contextExtensionsData
+	) throws TweedEntryWriteException {
 		try {
 			getWriterChain(entry).write(writer, value, entry, new TweedReadWriteContextImpl(contextExtensionsData));
 		} catch (TweedDataWriteException e) {
@@ -160,7 +194,8 @@ public class ReadWriteExtensionImpl implements ReadWriteExtension {
 	}
 
 	@Setter
-	private static class RegisteredExtensionDataImpl<U extends Patchwork<U>, E> implements RegisteredExtensionData<U, E> {
+	private static class RegisteredExtensionDataImpl<U extends Patchwork<@NonNull U>, E>
+			implements RegisteredExtensionData<U, E> {
 		private MethodHandle setter;
 
 		@Override
@@ -173,13 +208,13 @@ public class ReadWriteExtensionImpl implements ReadWriteExtension {
 		}
 	}
 
-	static <T> TweedEntryReader<T, ConfigEntry<T>> getReaderChain(ConfigEntry<T> elementEntry) {
+	static <T> TweedEntryReader<T, @NonNull ConfigEntry<T>> getReaderChain(ConfigEntry<T> elementEntry) {
 		//noinspection unchecked
-		return (TweedEntryReader<T, ConfigEntry<T>>) ((ReadWriteEntryDataExtension) elementEntry.extensionsData()).entryReaderChain();
+		return (TweedEntryReader<T, @NonNull ConfigEntry<T>>) ((ReadWriteEntryDataExtension) elementEntry.extensionsData()).entryReaderChain();
 	}
 
-	static <T> TweedEntryWriter<T, ConfigEntry<T>> getWriterChain(ConfigEntry<T> elementEntry) {
+	static <T> TweedEntryWriter<T, @NonNull ConfigEntry<T>> getWriterChain(ConfigEntry<T> elementEntry) {
 		//noinspection unchecked
-		return (TweedEntryWriter<T, ConfigEntry<T>>) ((ReadWriteEntryDataExtension) elementEntry.extensionsData()).entryWriterChain();
+		return (TweedEntryWriter<T, @NonNull ConfigEntry<T>>) ((ReadWriteEntryDataExtension) elementEntry.extensionsData()).entryWriterChain();
 	}
 }

tweed5-serde-extension/src/main/java/de/siphalor/tweed5/data/extension/impl/TweedEntryReaderWriterImpls.java

@@ -9,6 +9,9 @@ import de.siphalor.tweed5.dataapi.api.*;
 import lombok.AccessLevel;
 import lombok.NoArgsConstructor;
 import lombok.RequiredArgsConstructor;
+import org.jetbrains.annotations.Contract;
+import org.jspecify.annotations.NonNull;
+import org.jspecify.annotations.Nullable;
 
 import java.util.*;
 import java.util.function.BiConsumer;
@@ -32,7 +35,7 @@ public class TweedEntryReaderWriterImpls {
 	public static final TweedEntryReaderWriter<Object, ConfigEntry<Object>> NOOP_READER_WRITER = new NoopReaderWriter();
 
 	@RequiredArgsConstructor
-	public static class NullableReader<T, C extends ConfigEntry<T>> implements TweedEntryReader<T, C> {
+	public static class NullableReader<T extends @Nullable Object, C extends ConfigEntry<T>> implements TweedEntryReader<T, C> {
 		private final TweedEntryReader<T, C> delegate;
 
 		@Override
@@ -46,7 +49,7 @@ public class TweedEntryReaderWriterImpls {
 	}
 
 	@RequiredArgsConstructor
-	public static class NullableWriter<T, C extends ConfigEntry<T>> implements TweedEntryWriter<T, C> {
+	public static class NullableWriter<T extends @Nullable Object, C extends ConfigEntry<T>> implements TweedEntryWriter<T, C> {
 		private final TweedEntryWriter<T, C> delegate;
 
 		@Override
@@ -60,7 +63,7 @@ public class TweedEntryReaderWriterImpls {
 	}
 
 	@RequiredArgsConstructor
-	private static class PrimitiveReaderWriter<T> implements TweedEntryReaderWriter<T, ConfigEntry<T>> {
+	private static class PrimitiveReaderWriter<T extends @NonNull Object> implements TweedEntryReaderWriter<T, ConfigEntry<T>> {
 		private final Function<TweedDataToken, T> readerCall;
 		private final BiConsumer<TweedDataVisitor, T> writerCall;
 
@@ -70,13 +73,13 @@ public class TweedEntryReaderWriterImpls {
 		}
 
 		@Override
-		public void write(TweedDataVisitor writer, T value, ConfigEntry<T> entry, TweedWriteContext context) throws TweedEntryWriteException, TweedDataWriteException {
+		public void write(TweedDataVisitor writer, @Nullable T value, ConfigEntry<T> entry, TweedWriteContext context) throws TweedEntryWriteException, TweedDataWriteException {
 			requireNonNullWriteValue(value);
 			writerCall.accept(writer, value);
 		}
 	}
 
-	public static class CollectionReaderWriter<T, C extends Collection<T>> implements TweedEntryReaderWriter<C, CollectionConfigEntry<T, C>> {
+	public static class CollectionReaderWriter<T extends @NonNull Object, C extends Collection<T>> implements TweedEntryReaderWriter<C, CollectionConfigEntry<T, C>> {
 		@Override
 		public C read(TweedDataReader reader, CollectionConfigEntry<T, C> entry, TweedReadContext context) throws TweedEntryReadException, TweedDataReadException {
 			assertIsToken(reader.readToken(), TweedDataToken::isListStart, "Expected list start");
@@ -126,7 +129,7 @@ public class TweedEntryReaderWriterImpls {
 		}
 	}
 
-	public static class CompoundReaderWriter<T> implements TweedEntryReaderWriter<T, CompoundConfigEntry<T>> {
+	public static class CompoundReaderWriter<T extends @NonNull Object> implements TweedEntryReaderWriter<T, CompoundConfigEntry<T>> {
 		@Override
 		public T read(TweedDataReader reader, CompoundConfigEntry<T> entry, TweedReadContext context) throws TweedEntryReadException, TweedDataReadException {
 			assertIsToken(reader.readToken(), TweedDataToken::isMapStart, "Expected map start");
@@ -143,10 +146,8 @@ public class TweedEntryReaderWriterImpls {
 					//noinspection unchecked
 					ConfigEntry<Object> subEntry = (ConfigEntry<Object>) compoundEntries.get(key);
 					TweedEntryReader<Object, ConfigEntry<Object>> subEntryReaderChain = ReadWriteExtensionImpl.getReaderChain(subEntry);
-					if (subEntryReaderChain != null) {
+					Object subEntryValue = subEntryReaderChain.read(reader, subEntry, context);
-						Object subEntryValue = subEntryReaderChain.read(reader, subEntry, context);
+					entry.set(compoundValue, key, subEntryValue);
-						entry.set(compoundValue, key, subEntryValue);
-					}
 				} else {
 					throw new TweedEntryReadException("Unexpected token " + token + ": Expected map key or map end");
 				}
@@ -155,7 +156,7 @@ public class TweedEntryReaderWriterImpls {
 		}
 
 		@Override
-		public void write(TweedDataVisitor writer, T value, CompoundConfigEntry<T> entry, TweedWriteContext context) throws TweedEntryWriteException, TweedDataWriteException {
+		public void write(TweedDataVisitor writer, @Nullable T value, CompoundConfigEntry<T> entry, TweedWriteContext context) throws TweedEntryWriteException, TweedDataWriteException {
 			requireNonNullWriteValue(value);
 
 			writer.visitMapStart();
@@ -168,19 +169,17 @@ public class TweedEntryReaderWriterImpls {
 
 				TweedEntryWriter<Object, ConfigEntry<Object>> subEntryWriterChain = ReadWriteExtensionImpl.getWriterChain(subEntry);
 
-				if (subEntryWriterChain != null) {
+				writer.visitMapEntryKey(key);
-					writer.visitMapEntryKey(key);
+				subEntryWriterChain.write(writer, entry.get(value, key), subEntry, context);
-					subEntryWriterChain.write(writer, entry.get(value, key), subEntry, context);
-				}
 			}
 
 			writer.visitMapEnd();
 		}
 	}
 
-	public static class NoopReaderWriter implements TweedEntryReaderWriter<Object, ConfigEntry<Object>> {
+	public static class NoopReaderWriter implements TweedEntryReaderWriter<@Nullable Object, ConfigEntry<Object>> {
 		@Override
-		public Object read(TweedDataReader reader, ConfigEntry<Object> entry, TweedReadContext context) throws TweedDataReadException {
+		public @Nullable Object read(TweedDataReader reader, ConfigEntry<Object> entry, TweedReadContext context) throws TweedDataReadException {
 			TweedDataToken token = reader.readToken();
 			if (!token.isListStart() && !token.isMapStart()) {
 				return null;
@@ -209,7 +208,7 @@ public class TweedEntryReaderWriterImpls {
 		}
 
 		@Override
-		public void write(TweedDataVisitor writer, Object value, ConfigEntry<Object> entry, TweedWriteContext context) throws TweedDataWriteException {
+		public void write(TweedDataVisitor writer, @Nullable Object value, ConfigEntry<Object> entry, TweedWriteContext context) throws TweedDataWriteException {
 			writer.visitNull();
 		}
 
@@ -218,7 +217,8 @@ public class TweedEntryReaderWriterImpls {
 		}
 	}
 
-	private static <T> void requireNonNullWriteValue(T value) throws TweedEntryWriteException {
+	@Contract("null -> fail")
+	private static <T> void requireNonNullWriteValue(@Nullable T value) throws TweedEntryWriteException {
 		if (value == null) {
 			throw new TweedEntryWriteException("Unable to write null value");
 		}

tweed5-serde-extension/src/main/java/de/siphalor/tweed5/data/extension/impl/package-info.java

@@ -1,4 +1,6 @@
 @ApiStatus.Internal
+@NullMarked
 package de.siphalor.tweed5.data.extension.impl;
 
-import org.jetbrains.annotations.ApiStatus;
+import org.jetbrains.annotations.ApiStatus;
+import org.jspecify.annotations.NullMarked;

tweed5-serde-hjson/src/main/java/de/siphalor/tweed5/data/hjson/HjsonLexer.java

@@ -3,7 +3,7 @@ package de.siphalor.tweed5.data.hjson;
 import de.siphalor.tweed5.dataapi.api.TweedDataReadException;
 import lombok.RequiredArgsConstructor;
 import org.jetbrains.annotations.ApiStatus;
-import org.jetbrains.annotations.Nullable;
+import org.jspecify.annotations.Nullable;
 
 import java.io.IOException;
 import java.io.Reader;
@@ -58,8 +58,7 @@ public class HjsonLexer {
 		}
 	}
 
-	@Nullable
+	private HjsonLexerToken.@Nullable Type getTerminalTokenType(int codePoint) {
-	private HjsonLexerToken.Type getTerminalTokenType(int codePoint) {
 		switch (codePoint) {
 			case -1: return HjsonLexerToken.Type.EOF;
 			case '[': return HjsonLexerToken.Type.BRACKET_OPEN;
@@ -78,8 +77,7 @@ public class HjsonLexer {
 		return new HjsonLexerToken(tokenType, position, position, null);
 	}
 
-	@Nullable
+	private @Nullable HjsonLexerToken tryReadQuotedString(int codePoint) throws TweedDataReadException {
-	private HjsonLexerToken tryReadQuotedString(int codePoint) throws TweedDataReadException {
 		if (codePoint == '"') {
 			return readJsonQuotedString('"');
 		} else if (codePoint == '\'') {

tweed5-serde-hjson/src/main/java/de/siphalor/tweed5/data/hjson/HjsonLexerToken.java

@@ -3,7 +3,7 @@ package de.siphalor.tweed5.data.hjson;
 import lombok.EqualsAndHashCode;
 import lombok.Value;
 import org.jetbrains.annotations.ApiStatus;
-import org.jetbrains.annotations.Nullable;
+import org.jspecify.annotations.Nullable;
 
 @ApiStatus.Internal
 @Value
@@ -12,12 +12,10 @@ public class HjsonLexerToken {
 	HjsonReadPosition begin;
 	HjsonReadPosition end;
 	@EqualsAndHashCode.Exclude
-	@Nullable
+	@Nullable CharSequence content;
-	CharSequence content;
 
 	@EqualsAndHashCode.Include
-	@Nullable
+	public @Nullable String contentString() {
-	public String contentString() {
 		return content == null ? null : content.toString();
 	}
 

tweed5-serde-hjson/src/main/java/de/siphalor/tweed5/data/hjson/HjsonReader.java

@@ -1,6 +1,8 @@
 package de.siphalor.tweed5.data.hjson;
 
 import de.siphalor.tweed5.dataapi.api.*;
+import org.jspecify.annotations.NullUnmarked;
+import org.jspecify.annotations.Nullable;
 
 import java.util.*;
 import java.util.stream.Collectors;
@@ -10,9 +12,9 @@ public class HjsonReader implements TweedDataReader {
 	private final Deque<Context> contexts;
 	private State state = State.BEFORE_VALUE;
 
-	private HjsonLexerToken peekedLexerToken;
+	private @Nullable HjsonLexerToken peekedLexerToken;
 
-	private TweedDataToken peekedToken;
+	private @Nullable TweedDataToken peekedToken;
 
 	public HjsonReader(HjsonLexer lexer) {
 		this.lexer = lexer;
@@ -204,6 +206,7 @@ public class HjsonReader implements TweedDataReader {
 		};
 	}
 
+	@NullUnmarked
 	private TweedDataToken createNumberToken(HjsonLexerToken lexerToken) {
 		assert lexerToken.content() != null;
 		return new TweedDataToken() {
@@ -318,7 +321,7 @@ public class HjsonReader implements TweedDataReader {
 					tryLong = 0L;
 					boolean inFraction = false;
 					do {
-						tryLong = Math.addExact(Math.multiplyExact(tryLong, 10L), (long) (codePoint - '0'));
+						tryLong = Math.addExact(Math.multiplyExact(tryLong, 10L), codePoint - '0');
 						if (inFraction) {
 							fractionDigits++;
 						}
@@ -513,7 +516,7 @@ public class HjsonReader implements TweedDataReader {
 			@Override
 			public String readAsString() throws TweedDataReadException {
 				if (lexerToken.type() == HjsonLexerToken.Type.QUOTELESS_STRING || lexerToken.type() == HjsonLexerToken.Type.MULTILINE_STRING) {
-					return lexerToken.contentString();
+					return Objects.requireNonNull(lexerToken.contentString());
 				} else if (lexerToken.type() == HjsonLexerToken.Type.JSON_STRING) {
 					return readJsonString(lexerToken.content());
 				}
@@ -623,6 +626,7 @@ public class HjsonReader implements TweedDataReader {
 	}
 
 	private Context currentContext() {
+		assert contexts.peek() != null;
 		return contexts.peek();
 	}
 

tweed5-serde-hjson/src/main/java/de/siphalor/tweed5/data/hjson/HjsonSerde.java

@@ -4,19 +4,17 @@ import de.siphalor.tweed5.dataapi.api.TweedDataReader;
 import de.siphalor.tweed5.dataapi.api.TweedDataVisitor;
 import de.siphalor.tweed5.dataapi.api.TweedSerde;
 
-import java.io.IOException;
+import java.io.*;
-import java.io.InputStream;
-import java.io.OutputStream;
 
 public class HjsonSerde implements TweedSerde {
 	@Override
 	public TweedDataReader createReader(InputStream inputStream) {
-		return null;
+		return new HjsonReader(new HjsonLexer(new InputStreamReader(inputStream)));
 	}
 
 	@Override
 	public TweedDataVisitor createWriter(OutputStream outputStream) throws IOException {
-		return null;
+		return new HjsonWriter(new OutputStreamWriter(outputStream), new HjsonWriter.Options());
 	}
 
 	@Override

tweed5-serde-hjson/src/main/java/de/siphalor/tweed5/data/hjson/HjsonWriter.java

@@ -3,7 +3,6 @@ package de.siphalor.tweed5.data.hjson;
 import de.siphalor.tweed5.dataapi.api.TweedDataWriteException;
 import de.siphalor.tweed5.dataapi.api.TweedDataVisitor;
 import lombok.Data;
-import org.jetbrains.annotations.NotNull;
 
 import java.io.IOException;
 import java.io.Writer;
@@ -90,7 +89,7 @@ public class HjsonWriter implements TweedDataVisitor {
 	}
 
 	@Override
-	public void visitString(@NotNull String value) {
+	public void visitString(String value) {
 		beforeValueWrite();
 		writeStringValue(getValueStringStringType(value), value);
 		afterValueWrite();

tweed5-serde-hjson/src/main/java/de/siphalor/tweed5/data/hjson/package-info.java

@@ -0,0 +1,4 @@
+@NullMarked
+package de.siphalor.tweed5.data.hjson;
+
+import org.jspecify.annotations.NullMarked;

tweed5-type-utils/src/main/java/de/siphalor/tweed5/typeutils/api/type/ActualType.java

@@ -3,8 +3,7 @@ package de.siphalor.tweed5.typeutils.api.type;
 import lombok.AccessLevel;
 import lombok.Getter;
 import lombok.RequiredArgsConstructor;
-import org.jetbrains.annotations.NotNull;
+import org.jspecify.annotations.Nullable;
-import org.jetbrains.annotations.Nullable;
 
 import java.lang.annotation.Annotation;
 import java.lang.reflect.*;
@@ -27,13 +26,11 @@ public class ActualType<T> implements AnnotatedElement {
 	 * The {@link AnnotatedType} that represents the type that is actually in use (without parameters).
 	 */
 	@Getter(AccessLevel.PROTECTED)
-	@Nullable
+	private final @Nullable AnnotatedType usedType;
-	private final AnnotatedType usedType;
 	/**
 	 * The {@link AnnotatedParameterizedType} that represents the type that is actually in use with parameters.
 	 */
-	@Nullable
+	private final @Nullable AnnotatedParameterizedType usedParameterizedType;
-	private final AnnotatedParameterizedType usedParameterizedType;
 
 	/**
 	 * A representation of the layered annotations of this type.
@@ -45,7 +42,7 @@ public class ActualType<T> implements AnnotatedElement {
 	 * Internal cache for the resolved actual type parameters.
 	 */
 	@Nullable
-	private List<@NotNull ActualType<?>> resolvedParameters;
+	private List<ActualType<?>> resolvedParameters;
 
 	/**
 	 * Creates a basic actual type from just a declared class.
@@ -64,7 +61,7 @@ public class ActualType<T> implements AnnotatedElement {
 	 *
 	 * @throws UnsupportedOperationException when the given annotated type is not yet supported by this class
 	 */
-	public static ActualType<?> ofUsedType(@NotNull AnnotatedType annotatedType) throws UnsupportedOperationException {
+	public static ActualType<?> ofUsedType(AnnotatedType annotatedType) throws UnsupportedOperationException {
 		Class<?> clazz = getDeclaredClassForUsedType(annotatedType);
 
 		LayeredTypeAnnotations layeredTypeAnnotations = new LayeredTypeAnnotations();
@@ -83,7 +80,7 @@ public class ActualType<T> implements AnnotatedElement {
 	 *
 	 * @throws UnsupportedOperationException if the given parameter is not supported yet
 	 */
-	private static @NotNull Class<?> getDeclaredClassForUsedType(@NotNull AnnotatedType annotatedType) throws UnsupportedOperationException {
+	private static Class<?> getDeclaredClassForUsedType(AnnotatedType annotatedType) throws UnsupportedOperationException {
 		if (annotatedType.getType() instanceof Class) {
 			return (Class<?>) annotatedType.getType();
 		} else if (annotatedType.getType() instanceof ParameterizedType) {
@@ -102,24 +99,24 @@ public class ActualType<T> implements AnnotatedElement {
 	}
 
 	@Override
-	public <A extends Annotation> A getAnnotation(@NotNull Class<A> annotationClass) {
+	public <A extends Annotation> A getAnnotation(Class<A> annotationClass) {
 		return layeredTypeAnnotations.getAnnotation(annotationClass);
 	}
 
 	@Override
-	public @NotNull Annotation @NotNull [] getAnnotations() {
+	public Annotation[] getAnnotations() {
 		return layeredTypeAnnotations.getAnnotations();
 	}
 
 	@Override
-	public @NotNull Annotation @NotNull [] getDeclaredAnnotations() {
+	public Annotation[] getDeclaredAnnotations() {
 		return layeredTypeAnnotations.getDeclaredAnnotations();
 	}
 
 	/**
 	 * Resolves the type parameters of this type as {@link ActualType}s.
 	 */
-	public @NotNull List<@NotNull ActualType<?>> parameters() {
+	public List<ActualType<?>> parameters() {
 		if (resolvedParameters != null) {
 			return resolvedParameters;
 		} else if (usedParameterizedType == null) {
@@ -145,7 +142,7 @@ public class ActualType<T> implements AnnotatedElement {
 	 * @param targetClass the class to check
 	 * @return the list of type parameters if the given class is assignable from this type or {@code null} if not
 	 */
-	public @Nullable List<ActualType<?>> getTypesOfSuperArguments(@NotNull Class<?> targetClass) {
+	public @Nullable List<ActualType<?>> getTypesOfSuperArguments(Class<?> targetClass) {
 		if (targetClass.getTypeParameters().length == 0) {
 			if (targetClass.isAssignableFrom(declaredType)) {
 				return Collections.emptyList();
@@ -170,7 +167,7 @@ public class ActualType<T> implements AnnotatedElement {
 			return currentType;
 		}
 
-		List<@NotNull ActualType<?>> currentParameters = currentType.parameters();
+		List<ActualType<?>> currentParameters = currentType.parameters();
 
 		Map<String, AnnotatedType> paramMap;
 		if (currentParameters.isEmpty()) {
@@ -178,6 +175,8 @@ public class ActualType<T> implements AnnotatedElement {
 		} else {
 			paramMap = new HashMap<>();
 			for (int i = 0; i < currentParameters.size(); i++) {
+				// used types are always known in resolved parameters
+				//noinspection DataFlowIssue
 				paramMap.put(currentClass.getTypeParameters()[i].getName(), currentParameters.get(i).usedType());
 			}
 		}
@@ -185,7 +184,7 @@ public class ActualType<T> implements AnnotatedElement {
 		if (targetClass.isInterface()) {
 			for (AnnotatedType annotatedInterface : currentClass.getAnnotatedInterfaces()) {
 				ActualType<?> interfaceType = resolveTypeWithParameters(annotatedInterface, paramMap);
-				@Nullable ActualType<?> resultType = getViewOnSuperType(targetClass, interfaceType);
+				ActualType<?> resultType = getViewOnSuperType(targetClass, interfaceType);
 				if (resultType != null) {
 					return resultType;
 				}
@@ -193,7 +192,7 @@ public class ActualType<T> implements AnnotatedElement {
 		}
 		if (currentClass != Object.class && !currentClass.isInterface()) {
 			ActualType<?> superType = resolveTypeWithParameters(currentClass.getAnnotatedSuperclass(), paramMap);
-			@Nullable ActualType<?> resultType = getViewOnSuperType(targetClass, superType);
+			ActualType<?> resultType = getViewOnSuperType(targetClass, superType);
 			if (resultType != null) {
 				return resultType;
 			}
@@ -243,10 +242,10 @@ public class ActualType<T> implements AnnotatedElement {
 			appendAnnotationsToString(sb, usedType.getAnnotations());
 		}
 		sb.append(declaredType.getName());
-		List<@NotNull ActualType<?>> parameters = parameters();
+		List<ActualType<?>> parameters = parameters();
 		if (!parameters.isEmpty()) {
 			sb.append("<");
-			for (@NotNull ActualType<?> parameter : parameters) {
+			for (ActualType<?> parameter : parameters) {
 				sb.append(parameter);
 				sb.append(", ");
 			}
@@ -256,8 +255,8 @@ public class ActualType<T> implements AnnotatedElement {
 		return sb.toString();
 	}
 
-	private void appendAnnotationsToString(@NotNull StringBuilder sb, @NotNull Annotation[] annotations) {
+	private void appendAnnotationsToString(StringBuilder sb, Annotation[] annotations) {
-		for (@NotNull Annotation annotation : annotations) {
+		for (Annotation annotation : annotations) {
 			sb.append(annotation);
 			sb.append(' ');
 		}

tweed5-type-utils/src/main/java/de/siphalor/tweed5/typeutils/api/type/AnnotationRepeatType.java

@@ -2,12 +2,11 @@ package de.siphalor.tweed5.typeutils.api.type;
 
 import de.siphalor.tweed5.typeutils.impl.type.AnnotationRepeatTypeResolver;
 import lombok.Value;
-import org.jetbrains.annotations.NotNull;
 
 import java.lang.annotation.Annotation;
 
 public interface AnnotationRepeatType {
-	static AnnotationRepeatType getType(@NotNull Class<? extends Annotation> annotationClass) {
+	static AnnotationRepeatType getType(Class<? extends Annotation> annotationClass) {
 		return AnnotationRepeatTypeResolver.getType(annotationClass);
 	}
 

tweed5-type-utils/src/main/java/de/siphalor/tweed5/typeutils/api/type/LayeredTypeAnnotations.java

@@ -1,8 +1,7 @@
 package de.siphalor.tweed5.typeutils.api.type;
 
 import lombok.Value;
-import org.jetbrains.annotations.NotNull;
+import org.jspecify.annotations.Nullable;
-import org.jetbrains.annotations.Nullable;
 
 import java.lang.annotation.Annotation;
 import java.lang.reflect.AnnotatedElement;
@@ -11,7 +10,7 @@ import java.util.*;
 public class LayeredTypeAnnotations implements AnnotatedElement {
 	private static final Annotation[] EMPTY_ANNOTATIONS = new Annotation[0];
 
-	public static LayeredTypeAnnotations of(@NotNull TypeAnnotationLayer layer, @NotNull AnnotatedElement annotatedElement) {
+	public static LayeredTypeAnnotations of(TypeAnnotationLayer layer, AnnotatedElement annotatedElement) {
 		LayeredTypeAnnotations annotations = new LayeredTypeAnnotations();
 		annotations.layers.add(new Layer(layer, annotatedElement));
 		return annotations;
@@ -19,7 +18,7 @@ public class LayeredTypeAnnotations implements AnnotatedElement {
 
 	private final List<Layer> layers = new ArrayList<>();
 
-	public void appendLayerFrom(@NotNull TypeAnnotationLayer layer, @NotNull AnnotatedElement annotatedElement) {
+	public void appendLayerFrom(TypeAnnotationLayer layer, AnnotatedElement annotatedElement) {
 		int i;
 		for (i = 0; i < layers.size(); i++) {
 			if (layer.compareTo(layers.get(i).layer()) > 0) {
@@ -29,7 +28,7 @@ public class LayeredTypeAnnotations implements AnnotatedElement {
 		layers.add(i, new Layer(layer, annotatedElement));
 	}
 
-	public void prependLayerFrom(@NotNull TypeAnnotationLayer layer, @NotNull AnnotatedElement annotatedElement) {
+	public void prependLayerFrom(TypeAnnotationLayer layer, AnnotatedElement annotatedElement) {
 		int i;
 		for (i = 0; i < layers.size(); i++) {
 			if (layer.compareTo(layers.get(i).layer()) >= 0) {
@@ -40,7 +39,7 @@ public class LayeredTypeAnnotations implements AnnotatedElement {
 	}
 
 	@Override
-	public <T extends Annotation> T getAnnotation(@NotNull Class<T> annotationClass) {
+	public <T extends Annotation> T getAnnotation(Class<T> annotationClass) {
 		if (layers.isEmpty()) {
 			return null;
 		} else if (layers.size() == 1) {
@@ -62,7 +61,7 @@ public class LayeredTypeAnnotations implements AnnotatedElement {
 	}
 
 	@Override
-	public @NotNull Annotation @NotNull [] getAnnotations() {
+	public Annotation[] getAnnotations() {
 		if (layers.isEmpty()) {
 			return EMPTY_ANNOTATIONS;
 		} else if (layers.size() == 1) {
@@ -87,7 +86,7 @@ public class LayeredTypeAnnotations implements AnnotatedElement {
 	}
 
 	@Override
-	public @NotNull Annotation @NotNull [] getDeclaredAnnotations() {
+	public Annotation[] getDeclaredAnnotations() {
 		if (layers.isEmpty()) {
 			return EMPTY_ANNOTATIONS;
 		} else if (layers.size() == 1) {
@@ -111,7 +110,7 @@ public class LayeredTypeAnnotations implements AnnotatedElement {
 		return annotations.values().toArray(new Annotation[0]);
 	}
 
-	private static <T extends Annotation> @Nullable Class<? extends Annotation> getRepeatAlternativeAnnotation(@NotNull Class<T> annotationClass) {
+	private static <T extends Annotation> @Nullable Class<? extends Annotation> getRepeatAlternativeAnnotation(Class<T> annotationClass) {
 		AnnotationRepeatType annotationRepeatType = AnnotationRepeatType.getType(annotationClass);
 		Class<? extends Annotation> altAnnotationClass = null;
 		if (annotationRepeatType instanceof AnnotationRepeatType.Repeatable) {

tweed5-type-utils/src/main/java/de/siphalor/tweed5/typeutils/api/type/package-info.java

@@ -0,0 +1,4 @@
+@NullMarked
+package de.siphalor.tweed5.typeutils.api.type;
+
+import org.jspecify.annotations.NullMarked;

tweed5-type-utils/src/main/java/de/siphalor/tweed5/typeutils/impl/package-info.java

@@ -1,5 +1,6 @@
 @ApiStatus.Internal
-
+@NullMarked
 package de.siphalor.tweed5.typeutils.impl;
 
-import org.jetbrains.annotations.ApiStatus;
+import org.jetbrains.annotations.ApiStatus;
+import org.jspecify.annotations.NullMarked;

tweed5-type-utils/src/main/java/de/siphalor/tweed5/typeutils/impl/type/AnnotationRepeatTypeResolver.java

@@ -1,8 +1,7 @@
 package de.siphalor.tweed5.typeutils.impl.type;
 
 import de.siphalor.tweed5.typeutils.api.type.AnnotationRepeatType;
-import org.jetbrains.annotations.NotNull;
+import org.jspecify.annotations.Nullable;
-import org.jetbrains.annotations.Nullable;
 
 import java.lang.annotation.Annotation;
 import java.lang.annotation.Repeatable;
@@ -16,7 +15,7 @@ public class AnnotationRepeatTypeResolver {
 	private static final Map<Class<? extends Annotation>, AnnotationRepeatType> CACHE = new HashMap<>();
 	private static final ReadWriteLock CACHE_LOCK = new ReentrantReadWriteLock();
 
-	public static AnnotationRepeatType getType(@NotNull Class<? extends Annotation> annotationClass) {
+	public static AnnotationRepeatType getType(Class<? extends Annotation> annotationClass) {
 		CACHE_LOCK.readLock().lock();
 		try {
 			AnnotationRepeatType cachedValue = CACHE.get(annotationClass);
@@ -29,7 +28,7 @@ public class AnnotationRepeatTypeResolver {
 		return determineType(annotationClass);
 	}
 
-	private static AnnotationRepeatType determineType(@NotNull Class<? extends Annotation> annotationClass) {
+	private static AnnotationRepeatType determineType(Class<? extends Annotation> annotationClass) {
 		Class<? extends Annotation> container = getRepeatableContainerFromComponentAnnotation(annotationClass);
 		if (container != null) {
 			CACHE_LOCK.writeLock().lock();
@@ -64,8 +63,7 @@ public class AnnotationRepeatTypeResolver {
 		return AnnotationRepeatType.NonRepeatable.instance();
 	}
 
-	@Nullable
+	private static @Nullable Class<? extends Annotation> getRepeatableContainerFromComponentAnnotation(
-	private static Class<? extends Annotation> getRepeatableContainerFromComponentAnnotation(
 			Class<? extends Annotation> annotationClass
 	) {
 		Repeatable repeatableDeclaration = annotationClass.getAnnotation(Repeatable.class);
@@ -75,8 +73,7 @@ public class AnnotationRepeatTypeResolver {
 		return repeatableDeclaration.value();
 	}
 
-	@Nullable
+	private static @Nullable Class<? extends Annotation> getRepeatableComponentFromContainerAnnotation(
-	private static Class<? extends Annotation> getRepeatableComponentFromContainerAnnotation(
 			Class<? extends Annotation> annotationClass
 	) {
 		try {

tweed5-utils/src/main/java/de/siphalor/tweed5/utils/api/collection/ClassToInstanceMap.java

@@ -3,17 +3,18 @@ package de.siphalor.tweed5.utils.api.collection;
 import lombok.AccessLevel;
 import lombok.EqualsAndHashCode;
 import lombok.RequiredArgsConstructor;
-import org.jetbrains.annotations.NotNull;
+import org.jspecify.annotations.NonNull;
+import org.jspecify.annotations.Nullable;
 
 import java.util.*;
 
 @SuppressWarnings("unchecked")
 @EqualsAndHashCode
 @RequiredArgsConstructor(access = AccessLevel.PROTECTED)
-public class ClassToInstanceMap<T> implements Iterable<T> {
+public class ClassToInstanceMap<T extends @NonNull Object> implements Iterable<T> {
 	private final Map<Class<? extends T>, T> delegate;
 
-	public static <T> ClassToInstanceMap<T> backedBy(Map<Class<? extends T>, T> delegate) {
+	public static <T extends @NonNull Object> ClassToInstanceMap<T> backedBy(Map<Class<? extends T>, T> delegate) {
 		return new ClassToInstanceMap<>(delegate);
 	}
 
@@ -41,11 +42,11 @@ public class ClassToInstanceMap<T> implements Iterable<T> {
 		return (V) delegate.get(key);
 	}
 
-	public <V extends T> V put(@NotNull V value) {
+	public <V extends T> @Nullable V put(V value) {
 		return (V) delegate.put((Class<? extends T>) value.getClass(), value);
 	}
 
-	public <V extends T> V remove(Class<V> key) {
+	public <V extends T> @Nullable V remove(Class<V> key) {
 		return (V) delegate.remove(key);
 	}
 
@@ -60,7 +61,7 @@ public class ClassToInstanceMap<T> implements Iterable<T> {
 	public Set<T> values() {
 		return new AbstractSet<T>() {
 			@Override
-			public @NotNull Iterator<T> iterator() {
+			public Iterator<T> iterator() {
 				Iterator<Map.Entry<Class<? extends T>, T>> entryIterator = delegate.entrySet().iterator();
 				return new Iterator<T>() {
 					@Override
@@ -88,7 +89,7 @@ public class ClassToInstanceMap<T> implements Iterable<T> {
 	}
 
 	@Override
-	public @NotNull Iterator<T> iterator() {
+	public Iterator<T> iterator() {
 		return values().iterator();
 	}
 }

tweed5-utils/src/main/java/de/siphalor/tweed5/utils/api/collection/ClassToInstancesMultimap.java

@@ -1,7 +1,7 @@
 package de.siphalor.tweed5.utils.api.collection;
 
 import lombok.RequiredArgsConstructor;
-import org.jetbrains.annotations.NotNull;
+import org.jspecify.annotations.Nullable;
 
 import java.lang.reflect.Array;
 import java.util.*;
@@ -33,7 +33,7 @@ public class ClassToInstancesMultimap<T> implements Collection<T> {
 	}
 
 	@Override
-	public boolean contains(@NotNull Object o) {
+	public boolean contains(Object o) {
 		return delegate.getOrDefault(o.getClass(), Collections.emptyList()).contains(o);
 	}
 
@@ -42,10 +42,10 @@ public class ClassToInstancesMultimap<T> implements Collection<T> {
 	}
 
 	@Override
-	public @NotNull Iterator<T> iterator() {
+	public Iterator<T> iterator() {
 		return new Iterator<T>() {
 			private final Iterator<Map.Entry<Class<? extends T>, Collection<T>>> classIterator = delegate.entrySet().iterator();
-			private Iterator<? extends T> listIterator;
+			private @Nullable Iterator<? extends T> listIterator;
 			private boolean keptElement;
 			private boolean keptAnyElementInList;
 
@@ -82,14 +82,12 @@ public class ClassToInstancesMultimap<T> implements Collection<T> {
 	}
 
 	@Override
-	@NotNull
+	public Object[] toArray() {
-	public Object @NotNull [] toArray() {
 		return delegate.values().stream().flatMap(Collection::stream).toArray();
 	}
 
 	@Override
-	@NotNull
+	public <S> S[] toArray(S[] array) {
-	public <S> S @NotNull [] toArray(@NotNull S @NotNull [] array) {
 		Class<?> clazz = array.getClass().getComponentType();
 		return delegate.values().stream()
 				.flatMap(Collection::stream)
@@ -97,12 +95,12 @@ public class ClassToInstancesMultimap<T> implements Collection<T> {
 	}
 
 	@Override
-	public boolean add(@NotNull T value) {
+	public boolean add(T value) {
 		return delegate.computeIfAbsent(((Class<T>) value.getClass()), clazz -> collectionSupplier.get()).add(value);
 	}
 
 	@Override
-	public boolean remove(@NotNull Object value) {
+	public boolean remove(Object value) {
 		Collection<T> values = delegate.get(value.getClass());
 		if (values == null) {
 			return false;
@@ -116,19 +114,17 @@ public class ClassToInstancesMultimap<T> implements Collection<T> {
 		return false;
 	}
 
-	@NotNull
 	public <U extends T> Collection<U> getAll(Class<U> clazz) {
 		return (Collection<U>) Collections.unmodifiableCollection(delegate.getOrDefault(clazz, Collections.emptyList()));
 	}
 
-	@NotNull
 	public Collection<T> removeAll(Class<? extends T> clazz) {
 		Collection<T> removed = delegate.remove(clazz);
 		return removed == null ? Collections.emptyList() : Collections.unmodifiableCollection(removed);
 	}
 
 	@Override
-	public boolean containsAll(@NotNull Collection<?> values) {
+	public boolean containsAll(Collection<?> values) {
 		for (Object value : values) {
 			if (!contains(value)) {
 				return false;
@@ -138,7 +134,7 @@ public class ClassToInstancesMultimap<T> implements Collection<T> {
 	}
 
 	@Override
-	public boolean addAll(@NotNull Collection<? extends T> values) {
+	public boolean addAll(Collection<? extends T> values) {
 		boolean changed = false;
 		for (T value : values) {
 			changed = add(value) || changed;
@@ -147,7 +143,7 @@ public class ClassToInstancesMultimap<T> implements Collection<T> {
 	}
 
 	@Override
-	public boolean removeAll(@NotNull Collection<?> values) {
+	public boolean removeAll(Collection<?> values) {
 		boolean changed = false;
 		for (Object value : values) {
 			changed = remove(value) || changed;
@@ -156,7 +152,7 @@ public class ClassToInstancesMultimap<T> implements Collection<T> {
 	}
 
 	@Override
-	public boolean retainAll(@NotNull Collection<?> values) {
+	public boolean retainAll(Collection<?> values) {
 		Map<Class<?>, ? extends List<?>> valuesByClass = values.stream()
 				.collect(Collectors.groupingBy(Object::getClass));
 		delegate.putAll((Map<Class<? extends T>, List<T>>)(Object) valuesByClass);
@@ -178,37 +174,37 @@ public class ClassToInstancesMultimap<T> implements Collection<T> {
 		}
 
 		@Override
-		public @NotNull Iterator<T> iterator() {
+		public Iterator<T> iterator() {
 			return delegate.values().stream().flatMap(Collection::stream).iterator();
 		}
 
 		@Override
-		public boolean add(@NotNull T value) {
+		public boolean add(T value) {
 			throw createUnsupportedOperationException();
 		}
 
 		@Override
-		public boolean remove(@NotNull Object value) {
+		public boolean remove(Object value) {
 			throw createUnsupportedOperationException();
 		}
 
 		@Override
-		public @NotNull Collection<T> removeAll(Class<? extends T> clazz) {
+		public Collection<T> removeAll(Class<? extends T> clazz) {
 			throw createUnsupportedOperationException();
 		}
 
 		@Override
-		public boolean addAll(@NotNull Collection<? extends T> values) {
+		public boolean addAll(Collection<? extends T> values) {
 			throw createUnsupportedOperationException();
 		}
 
 		@Override
-		public boolean removeAll(@NotNull Collection<?> values) {
+		public boolean removeAll(Collection<?> values) {
 			throw createUnsupportedOperationException();
 		}
 
 		@Override
-		public boolean retainAll(@NotNull Collection<?> values) {
+		public boolean retainAll(Collection<?> values) {
 			throw createUnsupportedOperationException();
 		}
 

tweed5-utils/src/main/java/de/siphalor/tweed5/utils/api/collection/InheritanceMap.java

@@ -2,22 +2,24 @@ package de.siphalor.tweed5.utils.api.collection;
 
 import lombok.AccessLevel;
 import lombok.AllArgsConstructor;
+import org.jspecify.annotations.NonNull;
+import org.jspecify.annotations.Nullable;
 
 import java.util.*;
 
 @SuppressWarnings("unchecked")
 @AllArgsConstructor(access = AccessLevel.PROTECTED)
-public class InheritanceMap<T> {
+public class InheritanceMap<T extends @NonNull Object> {
 	private static final InheritanceMap<Object> EMPTY = unmodifiable(new InheritanceMap<>(Object.class));
 
 	private final Class<T> baseClass;
 	private final Map<T, Collection<Class<? extends T>>> instanceToClasses;
 	private final Map<Class<? extends T>, Collection<T>> classToInstances;
 
-	public static <T> InheritanceMap<T> empty() {
+	public static <T extends @NonNull Object> InheritanceMap<T> empty() {
 		return (InheritanceMap<T>) EMPTY;
 	}
-	public static <T> InheritanceMap<T> unmodifiable(InheritanceMap<T> map) {
+	public static <T extends @NonNull Object> InheritanceMap<T> unmodifiable(InheritanceMap<T> map) {
 		return new Unmodifiable<>(map);
 	}
 
@@ -49,7 +51,7 @@ public class InheritanceMap<T> {
 		return (Collection<V>) classToInstances.getOrDefault(clazz, Collections.emptyList());
 	}
 
-	public <V extends T> V getSingleInstance(Class<V> clazz) throws NonUniqueResultException {
+	public <V extends T> @Nullable V getSingleInstance(Class<V> clazz) throws NonUniqueResultException {
 		Collection<T> instances = classToInstances.getOrDefault(clazz, Collections.emptyList());
 		if (instances.isEmpty()) {
 			return null;
@@ -87,7 +89,7 @@ public class InheritanceMap<T> {
 		}
 	}
 	
-	public <V extends T> V removeInstance(V instance) {
+	public <V extends T> @Nullable V removeInstance(V instance) {
 		if (!instanceToClasses.containsKey(instance)) {
 			return null;
 		}
@@ -153,7 +155,7 @@ public class InheritanceMap<T> {
 		}
 	}
 
-	private static class Unmodifiable<T> extends InheritanceMap<T> {
+	private static class Unmodifiable<T extends @NonNull Object> extends InheritanceMap<T> {
 		public Unmodifiable(InheritanceMap<T> delegate) {
 			super(delegate.baseClass, delegate.instanceToClasses, delegate.classToInstances);
 		}

tweed5-utils/src/main/java/de/siphalor/tweed5/utils/api/collection/package-info.java

@@ -0,0 +1,4 @@
+@NullMarked
+package de.siphalor.tweed5.utils.api.collection;
+
+import org.jspecify.annotations.NullMarked;

tweed5-weaver-pojo-serde-extension/src/main/java/de/siphalor/tweed5/weaver/pojoext/serde/api/ReadWritePojoPostProcessor.java

@@ -7,7 +7,7 @@ import de.siphalor.tweed5.weaver.pojo.api.weaving.WeavingContext;
 import de.siphalor.tweed5.weaver.pojo.api.weaving.postprocess.TweedPojoWeavingPostProcessor;
 import de.siphalor.tweed5.weaver.pojoext.serde.impl.SerdePojoReaderWriterSpec;
 import lombok.extern.slf4j.Slf4j;
-import org.jetbrains.annotations.Nullable;
+import org.jspecify.annotations.Nullable;
 
 import java.lang.reflect.Array;
 import java.lang.reflect.Constructor;
@@ -80,8 +80,7 @@ public class ReadWritePojoPostProcessor implements TweedPojoWeavingPostProcessor
 		}
 	}
 
-	@Nullable
+	private @Nullable EntryReaderWriterDefinition createDefinitionFromEntryConfig(EntryReadWriteConfig entryConfig, WeavingContext context) {
-	private EntryReaderWriterDefinition createDefinitionFromEntryConfig(EntryReadWriteConfig entryConfig, WeavingContext context) {
 		String readerSpecText = entryConfig.reader().isEmpty() ? entryConfig.value() : entryConfig.reader();
 		String writerSpecText = entryConfig.writer().isEmpty() ? entryConfig.value() : entryConfig.writer();
 
@@ -98,14 +97,14 @@ public class ReadWritePojoPostProcessor implements TweedPojoWeavingPostProcessor
 			return null;
 		}
 
-		//noinspection unchecked
+		//noinspection unchecked,rawtypes
-		TweedEntryReader<?, ?> reader = readerSpec == null
+		TweedEntryReader<?, ?> reader = Optional.ofNullable(readerSpec)
-				? TweedEntryReaderWriterImpls.NOOP_READER_WRITER
+				.map((spec) -> resolveReaderWriterFromSpec((Class<TweedEntryReader<?, ?>>)(Object) TweedEntryReader.class, readerFactories, spec, context))
-				: resolveReaderWriterFromSpec((Class<TweedEntryReader<?, ?>>)(Object) TweedEntryReader.class, readerFactories, readerSpec, context);
+				.orElse(((TweedEntryReader) TweedEntryReaderWriterImpls.NOOP_READER_WRITER));
-		//noinspection unchecked
+		//noinspection unchecked,rawtypes
-		TweedEntryWriter<?, ?> writer = writerSpec == null
+		TweedEntryWriter<?, ?> writer = Optional.ofNullable(writerSpec)
-				? TweedEntryReaderWriterImpls.NOOP_READER_WRITER
+				.map((spec) -> resolveReaderWriterFromSpec((Class<TweedEntryWriter<?, ?>>)(Object) TweedEntryWriter.class, writerFactories, spec, context))
-				: resolveReaderWriterFromSpec((Class<TweedEntryWriter<?, ?>>)(Object) TweedEntryWriter.class, writerFactories, writerSpec, context);
+				.orElse(((TweedEntryWriter) TweedEntryReaderWriterImpls.NOOP_READER_WRITER));
 
 		return new EntryReaderWriterDefinition() {
 			@Override
@@ -120,8 +119,7 @@ public class ReadWritePojoPostProcessor implements TweedPojoWeavingPostProcessor
 		};
 	}
 
-	@Nullable
+	private @Nullable SerdePojoReaderWriterSpec specFromText(String specText, WeavingContext context) {
-	private SerdePojoReaderWriterSpec specFromText(String specText, WeavingContext context) {
 		if (specText.isEmpty()) {
 			return null;
 		}
@@ -137,7 +135,7 @@ public class ReadWritePojoPostProcessor implements TweedPojoWeavingPostProcessor
 		}
 	}
 
-	private <T> T resolveReaderWriterFromSpec(
+	private <T> @Nullable T resolveReaderWriterFromSpec(
 			Class<T> baseClass,
 			Map<String, TweedReaderWriterProvider.ReaderWriterFactory<T>> factories,
 			SerdePojoReaderWriterSpec spec,
@@ -152,17 +150,18 @@ public class ReadWritePojoPostProcessor implements TweedPojoWeavingPostProcessor
 		TweedReaderWriterProvider.ReaderWriterFactory<T> factory = factories.get(spec.identifier());
 
 		T instance;
-		if (factory != null) {
+		try {
-			instance = factory.create(arguments);
+			if (factory != null) {
-		} else {
+				instance = factory.create(arguments);
-			instance = loadClassIfExists(baseClass, spec.identifier(), arguments);
+			} else {
-		}
+				instance = loadClassIfExists(baseClass, spec.identifier(), arguments);
-
+			}
-		if (instance == null) {
+		} catch (Exception e) {
 			log.warn(
 					"Failed to resolve reader or writer factory \"{}\" for entry {}, entry will not be included in serde",
 					spec.identifier(),
-					context.path()
+					context.path(),
+					e
 			);
 			return null;
 		}
@@ -170,7 +169,7 @@ public class ReadWritePojoPostProcessor implements TweedPojoWeavingPostProcessor
 		return instance;
 	}
 
-	private <T> T loadClassIfExists(Class<T> baseClass, String className, T[] arguments) {
+	private <T> @Nullable T loadClassIfExists(Class<T> baseClass, String className, T[] arguments) {
 		try {
 			Class<?> clazz = Class.forName(className);
 			Class<?>[] argClasses = new Class<?>[arguments.length];

tweed5-weaver-pojo-serde-extension/src/main/java/de/siphalor/tweed5/weaver/pojoext/serde/api/package-info.java

@@ -0,0 +1,4 @@
+@NullMarked
+package de.siphalor.tweed5.weaver.pojoext.serde.api;
+
+import org.jspecify.annotations.NullMarked;

tweed5-weaver-pojo-serde-extension/src/main/java/de/siphalor/tweed5/weaver/pojoext/serde/impl/package-info.java

@@ -0,0 +1,4 @@
+@NullMarked
+package de.siphalor.tweed5.weaver.pojoext.serde.impl;
+
+import org.jspecify.annotations.NullMarked;

tweed5-weaver-pojo-serde-extension/src/test/java/de/siphalor/tweed5/weaver/pojoext/serde/WeaverPojoSerdeExtensionTest.java

@@ -57,13 +57,13 @@ class WeaverPojoSerdeExtensionTest {
 	public static class TestWriterProvider implements TweedReaderWriterProvider {
 		@Override
 		public void provideReaderWriters(ProviderContext context) {
-			context.registerWriterFactory("tweed5.test.dummy", delegates -> new TweedEntryWriter<Object, ConfigEntry<Object>>() {
+			context.registerWriterFactory("tweed5.test.dummy", delegates -> new TweedEntryWriter<Object, @NonNull ConfigEntry<Object>>() {
 				@Override
 				public void write(
-						TweedDataVisitor writer,
+						@NonNull TweedDataVisitor writer,
 						Object value,
 						ConfigEntry<Object> entry,
-						TweedWriteContext context
+						@NonNull TweedWriteContext context
 				) throws TweedDataWriteException {
 					writer.visitString("my cool custom writer");
 				}

tweed5-weaver-pojo/src/main/java/de/siphalor/tweed5/weaver/pojo/api/entry/WeavableCompoundConfigEntry.java

@@ -5,7 +5,7 @@ import de.siphalor.tweed5.core.api.entry.CompoundConfigEntry;
 import de.siphalor.tweed5.core.api.entry.ConfigEntry;
 import lombok.RequiredArgsConstructor;
 import lombok.Value;
-import org.jetbrains.annotations.NotNull;
+import org.jspecify.annotations.Nullable;
 
 import java.lang.invoke.MethodHandle;
 import java.util.function.Supplier;
@@ -28,9 +28,9 @@ public interface WeavableCompoundConfigEntry<T> extends CompoundConfigEntry<T> {
 	@Value
 	@RequiredArgsConstructor
 	class SubEntry {
-		@NotNull String name;
+		String name;
-		@NotNull ConfigEntry<?> configEntry;
+		ConfigEntry<?> configEntry;
-		@NotNull MethodHandle getter;
+		@Nullable MethodHandle getter;
-		@NotNull MethodHandle setter;
+		@Nullable MethodHandle setter;
 	}
 }

tweed5-weaver-pojo/src/main/java/de/siphalor/tweed5/weaver/pojo/api/entry/package-info.java

@@ -0,0 +1,4 @@
+@NullMarked
+package de.siphalor.tweed5.weaver.pojo.api.entry;
+
+import org.jspecify.annotations.NullMarked;

tweed5-weaver-pojo/src/main/java/de/siphalor/tweed5/weaver/pojo/api/weaving/CollectionPojoWeaver.java

@@ -9,8 +9,7 @@ import de.siphalor.tweed5.weaver.pojo.impl.entry.CollectionConfigEntryImpl;
 import de.siphalor.tweed5.weaver.pojo.impl.weaving.PojoWeavingException;
 import de.siphalor.tweed5.weaver.pojo.impl.weaving.collection.CollectionWeavingConfig;
 import de.siphalor.tweed5.weaver.pojo.impl.weaving.collection.CollectionWeavingConfigImpl;
-import org.jetbrains.annotations.NotNull;
+import org.jspecify.annotations.Nullable;
-import org.jetbrains.annotations.Nullable;
 
 import java.lang.invoke.MethodHandle;
 import java.lang.invoke.MethodHandles;
@@ -33,7 +32,7 @@ public class CollectionPojoWeaver implements TweedPojoWeaver {
 
 	@SuppressWarnings({"rawtypes", "unchecked"})
 	@Override
-	public @Nullable <T> ConfigEntry<T> weaveEntry(ActualType<T> valueType, WeavingContext context) {
+	public <T> @Nullable ConfigEntry<T> weaveEntry(ActualType<T> valueType, WeavingContext context) {
 		List<ActualType<?>> collectionTypeParams = valueType.getTypesOfSuperArguments(Collection.class);
 		if (collectionTypeParams == null) {
 			return null;
@@ -82,7 +81,7 @@ public class CollectionPojoWeaver implements TweedPojoWeaver {
 		return CollectionWeavingConfigImpl.withOverrides(parent, local);
 	}
 
-	private CollectionWeavingConfig createWeavingConfigFromAnnotations(@NotNull AnnotatedElement annotations) {
+	private @Nullable CollectionWeavingConfig createWeavingConfigFromAnnotations(AnnotatedElement annotations) {
 		CollectionWeaving annotation = annotations.getAnnotation(CollectionWeaving.class);
 		if (annotation == null) {
 			return null;

tweed5-weaver-pojo/src/main/java/de/siphalor/tweed5/weaver/pojo/api/weaving/CompoundPojoWeaver.java

@@ -15,8 +15,7 @@ import de.siphalor.tweed5.weaver.pojo.impl.weaving.PojoClassIntrospector;
 import de.siphalor.tweed5.weaver.pojo.impl.weaving.PojoWeavingException;
 import de.siphalor.tweed5.weaver.pojo.impl.weaving.compound.CompoundWeavingConfig;
 import de.siphalor.tweed5.weaver.pojo.impl.weaving.compound.CompoundWeavingConfigImpl;
-import org.jetbrains.annotations.NotNull;
+import org.jspecify.annotations.Nullable;
-import org.jetbrains.annotations.Nullable;
 
 import java.lang.invoke.MethodHandle;
 import java.lang.reflect.AnnotatedElement;
@@ -44,7 +43,7 @@ public class CompoundPojoWeaver implements TweedPojoWeaver {
 	}
 
 	@Override
-	public @Nullable <T> ConfigEntry<T> weaveEntry(ActualType<T> valueType, WeavingContext context) {
+	public <T> @Nullable ConfigEntry<T> weaveEntry(ActualType<T> valueType, WeavingContext context) {
 		if (context.annotations().getAnnotation(CompoundWeaving.class) == null) {
 			return null;
 		}
@@ -88,8 +87,7 @@ public class CompoundPojoWeaver implements TweedPojoWeaver {
 		return CompoundWeavingConfigImpl.withOverrides(parent, local);
 	}
 
-	@Nullable
+	private @Nullable CompoundWeavingConfig createWeavingConfigFromAnnotations(AnnotatedElement annotations) {
-	private CompoundWeavingConfig createWeavingConfigFromAnnotations(@NotNull AnnotatedElement annotations) {
 		CompoundWeaving annotation = annotations.getAnnotation(CompoundWeaving.class);
 		if (annotation == null) {
 			return null;
@@ -127,7 +125,6 @@ public class CompoundPojoWeaver implements TweedPojoWeaver {
 
 		//noinspection rawtypes
 		Class<? extends WeavableCompoundConfigEntry> annotationEntryClass = weavingConfig.compoundEntryClass();
-		@NotNull
 		Class<WeavableCompoundConfigEntry<C>> weavableEntryClass = (Class<WeavableCompoundConfigEntry<C>>) (
 				annotationEntryClass != null
 						? annotationEntryClass
@@ -143,7 +140,7 @@ public class CompoundPojoWeaver implements TweedPojoWeaver {
 		return property.getter() != null && (property.setter() != null || property.isFinal());
 	}
 
-	private @NotNull WeavableCompoundConfigEntry.SubEntry weaveCompoundSubEntry(
+	private WeavableCompoundConfigEntry.SubEntry weaveCompoundSubEntry(
 			PojoClassIntrospector.Property property,
 			WeavingContext.ExtensionsData newExtensionsData,
 			WeavingContext parentContext
@@ -167,7 +164,9 @@ public class CompoundPojoWeaver implements TweedPojoWeaver {
 		);
 	}
 
-	private @NotNull String convertName(String name, CompoundWeavingConfig weavingConfig) {
+	private String convertName(String name, CompoundWeavingConfig weavingConfig) {
+		// Always non-null at this point, since null values were already defaulted
+		//noinspection DataFlowIssue
 		return NamingFormat.convert(
 				name,
 				weavingConfig.compoundSourceNamingFormat(),
@@ -175,7 +174,7 @@ public class CompoundPojoWeaver implements TweedPojoWeaver {
 		);
 	}
 
-	private @NotNull NamingFormat getNamingFormatById(String id) {
+	private NamingFormat getNamingFormatById(String id) {
 		NamingFormat namingFormat = namingFormatCollector.namingFormats().get(id);
 		if (namingFormat == null) {
 			throw new PojoWeavingException(

tweed5-weaver-pojo/src/main/java/de/siphalor/tweed5/weaver/pojo/api/weaving/TrivialPojoWeaver.java

@@ -3,7 +3,6 @@ package de.siphalor.tweed5.weaver.pojo.api.weaving;
 import de.siphalor.tweed5.core.api.entry.ConfigEntry;
 import de.siphalor.tweed5.core.impl.entry.SimpleConfigEntryImpl;
 import de.siphalor.tweed5.typeutils.api.type.ActualType;
-import org.jetbrains.annotations.Nullable;
 
 public class TrivialPojoWeaver implements TweedPojoWeaver {
 	@Override
@@ -12,7 +11,7 @@ public class TrivialPojoWeaver implements TweedPojoWeaver {
 	}
 
 	@Override
-	public @Nullable <T> ConfigEntry<T> weaveEntry(ActualType<T> valueType, WeavingContext context) {
+	public <T> ConfigEntry<T> weaveEntry(ActualType<T> valueType, WeavingContext context) {
 		SimpleConfigEntryImpl<T> entry = new SimpleConfigEntryImpl<>(valueType.declaredType());
 		entry.seal(context.configContainer());
 		return entry;

tweed5-weaver-pojo/src/main/java/de/siphalor/tweed5/weaver/pojo/api/weaving/TweedPojoWeavingFunction.java

@@ -2,8 +2,7 @@ package de.siphalor.tweed5.weaver.pojo.api.weaving;
 
 import de.siphalor.tweed5.core.api.entry.ConfigEntry;
 import de.siphalor.tweed5.typeutils.api.type.ActualType;
-import org.jetbrains.annotations.NotNull;
+import org.jspecify.annotations.Nullable;
-import org.jetbrains.annotations.Nullable;
 
 @FunctionalInterface
 public interface TweedPojoWeavingFunction {
@@ -12,8 +11,7 @@ public interface TweedPojoWeavingFunction {
 	 * The returned config entry must be sealed.
 	 * @return The resulting, sealed config entry or {@code null}, if the weaving function is not applicable to the given parameters.
 	 */
-	@Nullable
+	<T> @Nullable ConfigEntry<T> weaveEntry(ActualType<T> valueType, WeavingContext context);
-	<T> ConfigEntry<T> weaveEntry(ActualType<T> valueType, WeavingContext context);
 
 	@FunctionalInterface
 	interface NonNull extends TweedPojoWeavingFunction {
@@ -25,6 +23,6 @@ public interface TweedPojoWeavingFunction {
 		 * @throws RuntimeException when a valid config entry could not be resolved.
 		 */
 		@Override
-		@NotNull <T> ConfigEntry<T> weaveEntry(ActualType<T> valueType, WeavingContext context);
+		<T> @org.jspecify.annotations.NonNull ConfigEntry<T> weaveEntry(ActualType<T> valueType, WeavingContext context);
 	}
 }

tweed5-weaver-pojo/src/main/java/de/siphalor/tweed5/weaver/pojo/api/weaving/WeavingContext.java

@@ -6,26 +6,19 @@ import de.siphalor.tweed5.patchwork.api.Patchwork;
 import de.siphalor.tweed5.typeutils.api.type.ActualType;
 import lombok.*;
 import lombok.experimental.Accessors;
-import org.jetbrains.annotations.NotNull;
+import org.jspecify.annotations.Nullable;
-import org.jetbrains.annotations.Nullable;
 
 import java.lang.reflect.AnnotatedElement;
 import java.util.Arrays;
 
 @Value
 public class WeavingContext implements TweedPojoWeavingFunction.NonNull {
-	@Nullable
+	@Nullable WeavingContext parent;
-	WeavingContext parent;
 	@Getter(AccessLevel.NONE)
-	@NotNull
 	TweedPojoWeavingFunction.NonNull weavingFunction;
-	@NotNull
 	ConfigContainer<?> configContainer;
-	@NotNull
 	String[] path;
-	@NotNull
 	ExtensionsData extensionsData;
-	@NotNull
 	AnnotatedElement annotations;
 
 	public static Builder builder(TweedPojoWeavingFunction.NonNull weavingFunction, ConfigContainer<?> configContainer) {
@@ -36,14 +29,14 @@ public class WeavingContext implements TweedPojoWeavingFunction.NonNull {
 		return new Builder(null, weavingFunction, configContainer, new String[]{ baseName });
 	}
 
-	public Builder subContextBuilder(@NotNull String subPathName) {
+	public Builder subContextBuilder(String subPathName) {
 		String[] newPath = Arrays.copyOf(path, path.length + 1);
 		newPath[path.length] = subPathName;
 		return new Builder(this, weavingFunction, configContainer, newPath).extensionsData(extensionsData);
 	}
 
 	@Override
-	public @NotNull <T> ConfigEntry<T> weaveEntry(ActualType<T> valueType, WeavingContext context) {
+	public <T> ConfigEntry<T> weaveEntry(ActualType<T> valueType, WeavingContext context) {
 		return weavingFunction.weaveEntry(valueType, context);
 	}
 

tweed5-weaver-pojo/src/main/java/de/siphalor/tweed5/weaver/pojo/api/weaving/package-info.java

@@ -0,0 +1,4 @@
+@NullMarked
+package de.siphalor.tweed5.weaver.pojo.api.weaving;
+
+import org.jspecify.annotations.NullMarked;

tweed5-weaver-pojo/src/main/java/de/siphalor/tweed5/weaver/pojo/api/weaving/postprocess/package-info.java

@@ -0,0 +1,4 @@
+@NullMarked
+package de.siphalor.tweed5.weaver.pojo.api.weaving.postprocess;
+
+import org.jspecify.annotations.NullMarked;

tweed5-weaver-pojo/src/main/java/de/siphalor/tweed5/weaver/pojo/impl/entry/CollectionConfigEntryImpl.java

@@ -9,6 +9,7 @@ import lombok.EqualsAndHashCode;
 import lombok.Getter;
 import lombok.ToString;
 import org.jetbrains.annotations.NotNull;
+import org.jspecify.annotations.Nullable;
 
 import java.util.Collection;
 import java.util.function.IntFunction;
@@ -18,7 +19,7 @@ import java.util.function.IntFunction;
 @ToString(callSuper = true)
 public class CollectionConfigEntryImpl<E, T extends Collection<E>> extends BaseConfigEntry<T> implements WeavableCollectionConfigEntry<E, T> {
 	private final IntFunction<T> constructor;
-	private ConfigEntry<E> elementEntry;
+	private @Nullable ConfigEntry<E> elementEntry;
 
 	public CollectionConfigEntryImpl(@NotNull Class<T> valueClass, IntFunction<T> constructor) {
 		super(valueClass);

tweed5-weaver-pojo/src/main/java/de/siphalor/tweed5/weaver/pojo/impl/entry/StaticPojoCompoundConfigEntry.java

@@ -5,7 +5,6 @@ import de.siphalor.tweed5.core.api.entry.ConfigEntry;
 import de.siphalor.tweed5.core.api.entry.ConfigEntryValueVisitor;
 import de.siphalor.tweed5.core.api.entry.ConfigEntryVisitor;
 import de.siphalor.tweed5.weaver.pojo.api.entry.WeavableCompoundConfigEntry;
-import org.jetbrains.annotations.NotNull;
 
 import java.util.Collections;
 import java.util.LinkedHashMap;
@@ -17,7 +16,7 @@ public class StaticPojoCompoundConfigEntry<T> extends BaseConfigEntry<T> impleme
 	private final Map<String, SubEntry> subEntries = new LinkedHashMap<>();
 	private final Map<String, ConfigEntry<?>> subConfigEntries = new LinkedHashMap<>();
 
-	public StaticPojoCompoundConfigEntry(@NotNull Class<T> valueClass, @NotNull Supplier<T> noArgsConstructor) {
+	public StaticPojoCompoundConfigEntry(Class<T> valueClass, Supplier<T> noArgsConstructor) {
 		super(valueClass);
 		this.noArgsConstructor = noArgsConstructor;
 	}
@@ -91,7 +90,7 @@ public class StaticPojoCompoundConfigEntry<T> extends BaseConfigEntry<T> impleme
 			subEntries.forEach((key, entry) -> {
 				if (visitor.enterCompoundSubEntry(key)) {
 					try {
-						Object subValue = entry.getter().invokeExact(value);
+						Object subValue = entry.getter().invoke(value);
 						//noinspection unchecked
 						visitor.visitEntry((ConfigEntry<Object>) entry.configEntry(), subValue);
 					} catch (Throwable e) {
@@ -103,11 +102,11 @@ public class StaticPojoCompoundConfigEntry<T> extends BaseConfigEntry<T> impleme
 	}
 
 	@Override
-	public @NotNull T deepCopy(@NotNull T value) {
+	public T deepCopy(T value) {
 		T copy = instantiateCompoundValue();
 		for (SubEntry subEntry : subEntries.values()) {
 			try {
-				Object subValue = subEntry.getter().invokeExact(value);
+				Object subValue = subEntry.getter().invoke(value);
 				subEntry.setter().invoke(copy, subValue);
 			} catch (Throwable e) {
 				throw new RuntimeException("Failed to copy value of sub entry \"" + subEntry.name() + "\"", e);

tweed5-weaver-pojo/src/main/java/de/siphalor/tweed5/weaver/pojo/impl/entry/package-info.java

@@ -0,0 +1,4 @@
+@NullMarked
+package de.siphalor.tweed5.weaver.pojo.impl.entry;
+
+import org.jspecify.annotations.NullMarked;

tweed5-weaver-pojo/src/main/java/de/siphalor/tweed5/weaver/pojo/impl/weaving/PojoClassIntrospector.java

@@ -5,7 +5,7 @@ import lombok.Builder;
 import lombok.RequiredArgsConstructor;
 import lombok.Value;
 import lombok.extern.slf4j.Slf4j;
-import org.jetbrains.annotations.Nullable;
+import org.jspecify.annotations.Nullable;
 
 import java.lang.invoke.MethodHandle;
 import java.lang.invoke.MethodHandles;
@@ -23,7 +23,7 @@ public class PojoClassIntrospector {
 	private final Class<?> clazz;
 	private final MethodHandles.Lookup lookup = MethodHandles.publicLookup();
 
-	private Map<String, Property> properties;
+	private @Nullable Map<String, Property> properties;
 
 	public static PojoClassIntrospector forClass(Class<?> clazz) {
 		if ((clazz.getModifiers() & Modifier.PUBLIC) == 0) {

tweed5-weaver-pojo/src/main/java/de/siphalor/tweed5/weaver/pojo/impl/weaving/TweedPojoWeaverBootstrapper.java

@@ -15,7 +15,7 @@ import de.siphalor.tweed5.weaver.pojo.api.weaving.WeavingContext;
 import de.siphalor.tweed5.weaver.pojo.api.weaving.postprocess.TweedPojoWeavingPostProcessor;
 import lombok.*;
 import lombok.extern.slf4j.Slf4j;
-import org.jetbrains.annotations.Nullable;
+import org.jspecify.annotations.Nullable;
 
 import java.lang.annotation.Annotation;
 import java.lang.invoke.MethodHandle;

tweed5-weaver-pojo/src/main/java/de/siphalor/tweed5/weaver/pojo/impl/weaving/collection/CollectionWeavingConfig.java

@@ -1,10 +1,9 @@
 package de.siphalor.tweed5.weaver.pojo.impl.weaving.collection;
 
 import de.siphalor.tweed5.weaver.pojo.api.entry.WeavableCollectionConfigEntry;
-import org.jetbrains.annotations.Nullable;
+import org.jspecify.annotations.Nullable;
 
 public interface CollectionWeavingConfig {
 	@SuppressWarnings("rawtypes")
-	@Nullable
+	@Nullable Class<? extends WeavableCollectionConfigEntry> collectionEntryClass();
-	Class<? extends WeavableCollectionConfigEntry> collectionEntryClass();
 }

tweed5-weaver-pojo/src/main/java/de/siphalor/tweed5/weaver/pojo/impl/weaving/collection/CollectionWeavingConfigImpl.java

@@ -3,15 +3,14 @@ package de.siphalor.tweed5.weaver.pojo.impl.weaving.collection;
 import de.siphalor.tweed5.weaver.pojo.api.entry.WeavableCollectionConfigEntry;
 import lombok.Builder;
 import lombok.Value;
-import org.jetbrains.annotations.Nullable;
+import org.jspecify.annotations.Nullable;
 
 @Builder
 @Value
 public class CollectionWeavingConfigImpl implements CollectionWeavingConfig {
 
 	@SuppressWarnings("rawtypes")
-	@Nullable
+	@Nullable Class<? extends WeavableCollectionConfigEntry> collectionEntryClass;
-	Class<? extends WeavableCollectionConfigEntry> collectionEntryClass;
 
 	public static CollectionWeavingConfigImpl withOverrides(CollectionWeavingConfig self, CollectionWeavingConfig overrides) {
 		return CollectionWeavingConfigImpl.builder()

tweed5-weaver-pojo/src/main/java/de/siphalor/tweed5/weaver/pojo/impl/weaving/collection/package-info.java

@@ -0,0 +1,4 @@
+@NullMarked
+package de.siphalor.tweed5.weaver.pojo.impl.weaving.collection;
+
+import org.jspecify.annotations.NullMarked;

tweed5-weaver-pojo/src/main/java/de/siphalor/tweed5/weaver/pojo/impl/weaving/compound/CompoundWeavingConfig.java

@@ -2,14 +2,13 @@ package de.siphalor.tweed5.weaver.pojo.impl.weaving.compound;
 
 import de.siphalor.tweed5.namingformat.api.NamingFormat;
 import de.siphalor.tweed5.weaver.pojo.api.entry.WeavableCompoundConfigEntry;
-import org.jetbrains.annotations.Nullable;
+import org.jspecify.annotations.Nullable;
 
 public interface CompoundWeavingConfig {
-	NamingFormat compoundSourceNamingFormat();
+	@Nullable NamingFormat compoundSourceNamingFormat();
 
-	NamingFormat compoundTargetNamingFormat();
+	@Nullable NamingFormat compoundTargetNamingFormat();
 
 	@SuppressWarnings("rawtypes")
-	@Nullable
+	@Nullable Class<? extends WeavableCompoundConfigEntry> compoundEntryClass();
-	Class<? extends WeavableCompoundConfigEntry> compoundEntryClass();
 }

tweed5-weaver-pojo/src/main/java/de/siphalor/tweed5/weaver/pojo/impl/weaving/compound/CompoundWeavingConfigImpl.java

@@ -4,17 +4,16 @@ import de.siphalor.tweed5.namingformat.api.NamingFormat;
 import de.siphalor.tweed5.weaver.pojo.api.entry.WeavableCompoundConfigEntry;
 import lombok.Builder;
 import lombok.Value;
-import org.jetbrains.annotations.Nullable;
+import org.jspecify.annotations.Nullable;
 
 @Builder
 @Value
 public class CompoundWeavingConfigImpl implements CompoundWeavingConfig {
 
-	NamingFormat compoundSourceNamingFormat;
+	@Nullable NamingFormat compoundSourceNamingFormat;
-	NamingFormat compoundTargetNamingFormat;
+	@Nullable NamingFormat compoundTargetNamingFormat;
 	@SuppressWarnings("rawtypes")
-	@Nullable
+	@Nullable Class<? extends WeavableCompoundConfigEntry> compoundEntryClass;
-	Class<? extends WeavableCompoundConfigEntry> compoundEntryClass;
 
 	public static CompoundWeavingConfigImpl withOverrides(CompoundWeavingConfig self, CompoundWeavingConfig overrides) {
 		return CompoundWeavingConfigImpl.builder()

tweed5-weaver-pojo/src/main/java/de/siphalor/tweed5/weaver/pojo/impl/weaving/compound/package-info.java

@@ -0,0 +1,4 @@
+@NullMarked
+package de.siphalor.tweed5.weaver.pojo.impl.weaving.compound;
+
+import org.jspecify.annotations.NullMarked;

tweed5-weaver-pojo/src/main/java/de/siphalor/tweed5/weaver/pojo/impl/weaving/package-info.java

@@ -0,0 +1,4 @@
+@NullMarked
+package de.siphalor.tweed5.weaver.pojo.impl.weaving;
+
+import org.jspecify.annotations.NullMarked;