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Add support for Log4j API and SLF4J (#177)

The logging backends supported by the default `LogFactoryImpl` have all
reached their end-of-life (except JUL and `SimpleLog`). Third-generation
logging backends, such as Log4j Core, support multiple logger contexts
per application and therefore can not be handled by the simplified
caching mechanism in `LogFactoryImpl`.

This PR introduces two new `LogFactory` implementations,
`Log4j2LogFactory` and `Slf4jLogFactory`, that forward messages to the
Log4j API and SLF4J.

During initialization the three existing factories are checked in the
following order:
 1. the `Log4j2LogFactory` has highest priority, since the Log4j API can
    faithfully transmit messages of type `Object`,
 2. the `Slf4jLogFactory` is the next choice. However, if the
    Log4j-to-SLF4J bridge is present we log directly through SLF4J
    instead of the Log4j API.
 3. the legacy `LogFactoryImpl` has lowest priority.
This commit is contained in:
Piotr P. Karwasz
2023-11-03 16:19:14 +01:00
committed by GitHub
parent b7f50da2aa
commit 946711e0a6
9 changed files with 1016 additions and 6 deletions

View File

@@ -92,6 +92,13 @@ public abstract class LogFactory {
*/
public static final String FACTORY_PROPERTY = "org.apache.commons.logging.LogFactory";
private static final String FACTORY_LOG4J_API = "org.apache.commons.logging.impl.Log4jApiLogFactory";
private static final String LOG4J_API_LOGGER = "org.apache.logging.log4j.Logger";
private static final String LOG4J_TO_SLF4J_BRIDGE = "org.apache.logging.slf4j.SLF4JProvider";
private static final String FACTORY_SLF4J = "org.apache.commons.logging.impl.Slf4jLogFactory";
private static final String SLF4J_API_LOGGER = "org.slf4j.Logger";
/**
* The fully qualified class name of the fallback {@code LogFactory}
* implementation class to use, if no other can be found.
@@ -932,7 +939,29 @@ public abstract class LogFactory {
}
}
// Fourth, try the fallback implementation class
// Fourth, try one of the 3 provided factories
try {
// We prefer Log4j API, since it does not stringify objects.
if (factory == null && isClassAvailable(LOG4J_API_LOGGER, baseClassLoader)) {
// If the Log4j API is redirected to SLF4J, we use SLF4J directly.
if (isClassAvailable(LOG4J_TO_SLF4J_BRIDGE, baseClassLoader)) {
logDiagnostic(
"[LOOKUP] Log4j API to SLF4J redirection detected. Loading the SLF4J LogFactory implementation '" + FACTORY_SLF4J + "'.");
factory = newFactory(FACTORY_SLF4J, baseClassLoader, contextClassLoader);
} else {
logDiagnostic("[LOOKUP] Log4j API detected. Loading the Log4j API LogFactory implementation '" + FACTORY_LOG4J_API + "'.");
factory = newFactory(FACTORY_LOG4J_API, baseClassLoader, contextClassLoader);
}
}
if (factory == null && isClassAvailable(SLF4J_API_LOGGER, baseClassLoader)) {
logDiagnostic("[LOOKUP] SLF4J detected. Loading the SLF4J LogFactory implementation '" + FACTORY_SLF4J + "'.");
factory = newFactory(FACTORY_SLF4J, baseClassLoader, contextClassLoader);
}
} catch (final Exception e) {
logDiagnostic("[LOOKUP] An exception occurred while creating LogFactory: " + e.getMessage());
}
if (factory == null) {
if (isDiagnosticsEnabled()) {
@@ -973,6 +1002,18 @@ public abstract class LogFactory {
return factory;
}
private static boolean isClassAvailable(final String className, final ClassLoader classLoader) {
final ClassLoader loader = LogFactory.class.getClassLoader();
logDiagnostic("Checking if class '" + className + "' is available in class loader " + objectId(loader));
try {
Class.forName(className, true, classLoader);
return true;
} catch (final ClassNotFoundException | LinkageError e) {
logDiagnostic("Failed to load class '" + className + "' from class loader " + objectId(loader) + ": " + e.getMessage());
}
return false;
}
/**
* Convenience method to return a named logger, without the application having to care about factories.
*

View File

@@ -40,6 +40,8 @@ import org.apache.log4j.Priority;
* Log4J1.3 is expected to change Level so it no longer extends Priority, which is
* a non-binary-compatible change. The class generated by compiling this code against
* log4j 1.2 will therefore not run against log4j 1.3.
*
* @deprecated Scheduled for removal since version 1.x of Log4j has reached end-of-life.
*/
public class Log4JLogger implements Log, Serializable {

View File

@@ -0,0 +1,231 @@
/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.commons.logging.impl;
import java.io.IOException;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ConcurrentMap;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.logging.log4j.Level;
import org.apache.logging.log4j.LogManager;
import org.apache.logging.log4j.Marker;
import org.apache.logging.log4j.MarkerManager;
import org.apache.logging.log4j.spi.AbstractLoggerAdapter;
import org.apache.logging.log4j.spi.ExtendedLogger;
import org.apache.logging.log4j.spi.LoggerAdapter;
import org.apache.logging.log4j.spi.LoggerContext;
import org.apache.logging.log4j.util.StackLocatorUtil;
/**
* Logger factory hardcoded to send everything to Log4j API.
* <p>
* Based on the `log4j-jcl` artifact from Apache Logging Services.
* </p>
*
* @since 1.3
*/
public final class Log4jApiLogFactory extends LogFactory {
private static final String[] EMPTY_ARRAY = new String[0];
/**
* Marker used by all messages coming from Apache Commons Logging.
*/
private static final Marker MARKER = MarkerManager.getMarker("COMMONS-LOGGING");
/**
* Caches Log instances
*/
private final LoggerAdapter<Log> adapter = new LogAdapter();
private final ConcurrentMap<String, Object> attributes = new ConcurrentHashMap<>();
@Override
public Log getInstance(final String name) {
return adapter.getLogger(name);
}
@Override
public Object getAttribute(final String name) {
return attributes.get(name);
}
@Override
public String[] getAttributeNames() {
return attributes.keySet().toArray(EMPTY_ARRAY);
}
@Override
public Log getInstance(final Class clazz) {
return getInstance(clazz.getName());
}
/**
* This method is supposed to clear all loggers. In this implementation it will clear all the logger
* wrappers but the loggers managed by the underlying logger context will not be.
*/
@Override
public void release() {
try {
adapter.close();
} catch (final IOException ignored) {
}
}
@Override
public void removeAttribute(final String name) {
attributes.remove(name);
}
@Override
public void setAttribute(final String name, final Object value) {
if (value != null) {
attributes.put(name, value);
} else {
removeAttribute(name);
}
}
private static final class LogAdapter extends AbstractLoggerAdapter<Log> {
@Override
protected Log newLogger(final String name, final LoggerContext context) {
return new Log4j2Log(context.getLogger(name));
}
@Override
protected LoggerContext getContext() {
return getContext(LogManager.getFactory().isClassLoaderDependent() ? StackLocatorUtil.getCallerClass(
LogFactory.class) : null);
}
}
private static final class Log4j2Log implements Log {
private static final String FQCN = Log4j2Log.class.getName();
private final ExtendedLogger logger;
public Log4j2Log(final ExtendedLogger logger) {
this.logger = logger;
}
@Override
public boolean isDebugEnabled() {
return isEnabled(Level.DEBUG);
}
@Override
public boolean isErrorEnabled() {
return isEnabled(Level.ERROR);
}
@Override
public boolean isFatalEnabled() {
return isEnabled(Level.FATAL);
}
@Override
public boolean isInfoEnabled() {
return isEnabled(Level.INFO);
}
@Override
public boolean isTraceEnabled() {
return isEnabled(Level.TRACE);
}
@Override
public boolean isWarnEnabled() {
return isEnabled(Level.WARN);
}
@Override
public void trace(final Object message) {
logIfEnabled(Level.TRACE, message, null);
}
@Override
public void trace(final Object message, final Throwable t) {
logIfEnabled(Level.TRACE, message, t);
}
@Override
public void debug(final Object message) {
logIfEnabled(Level.DEBUG, message, null);
}
@Override
public void debug(final Object message, final Throwable t) {
logIfEnabled(Level.DEBUG, message, t);
}
@Override
public void info(final Object message) {
logIfEnabled(Level.INFO, message, null);
}
@Override
public void info(final Object message, final Throwable t) {
logIfEnabled(Level.INFO, message, t);
}
@Override
public void warn(final Object message) {
logIfEnabled(Level.WARN, message, null);
}
@Override
public void warn(final Object message, final Throwable t) {
logIfEnabled(Level.WARN, message, t);
}
@Override
public void error(final Object message) {
logIfEnabled(Level.ERROR, message, null);
}
@Override
public void error(final Object message, final Throwable t) {
logIfEnabled(Level.ERROR, message, t);
}
@Override
public void fatal(final Object message) {
logIfEnabled(Level.FATAL, message, null);
}
@Override
public void fatal(final Object message, final Throwable t) {
logIfEnabled(Level.FATAL, message, t);
}
private boolean isEnabled(final Level level) {
return logger.isEnabled(level, MARKER, null);
}
private void logIfEnabled(final Level level, final Object message, final Throwable t) {
if (message instanceof CharSequence) {
logger.logIfEnabled(FQCN, level, MARKER, (CharSequence) message, t);
} else {
logger.logIfEnabled(FQCN, level, MARKER, message, t);
}
}
}
}

View File

@@ -0,0 +1,323 @@
/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.commons.logging.impl;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ConcurrentMap;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogConfigurationException;
import org.apache.commons.logging.LogFactory;
import org.slf4j.ILoggerFactory;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.slf4j.Marker;
import org.slf4j.MarkerFactory;
import org.slf4j.spi.LocationAwareLogger;
import static org.slf4j.spi.LocationAwareLogger.DEBUG_INT;
import static org.slf4j.spi.LocationAwareLogger.ERROR_INT;
import static org.slf4j.spi.LocationAwareLogger.INFO_INT;
import static org.slf4j.spi.LocationAwareLogger.TRACE_INT;
import static org.slf4j.spi.LocationAwareLogger.WARN_INT;
/**
* Logger factory hardcoded to send everything to SLF4J.
*
* @since 1.3
*/
public final class Slf4jLogFactory extends LogFactory {
private static final Object[] EMPTY_OBJECT_ARRAY = new Object[0];
private static final String[] EMPTY_STRING_ARRAY = new String[0];
/**
* Marker used by all messages coming from Apache Commons Logging.
*/
private static final Marker MARKER = MarkerFactory.getMarker("COMMONS-LOGGING");
/**
* Caches Log instances.
* <p>
* The SLF4J reference implementation (Logback) has a single logger context, so each call to
* {@link #getInstance(String)}
* should give the same result.
* </p>
*/
private final ConcurrentMap<String, Log> loggers = new ConcurrentHashMap<>();
private final ConcurrentMap<String, Object> attributes = new ConcurrentHashMap<>();
@Override
public Log getInstance(final String name) {
return loggers.computeIfAbsent(name, n -> {
final Logger logger = LoggerFactory.getLogger(n);
return logger instanceof LocationAwareLogger ? new Slf4jLocationAwareLog((LocationAwareLogger) logger) : new Slf4jLog(
logger);
});
}
@Override
public Object getAttribute(final String name) {
return attributes.get(name);
}
@Override
public String[] getAttributeNames() {
return attributes.keySet().toArray(EMPTY_STRING_ARRAY);
}
@Override
public Log getInstance(final Class clazz) throws LogConfigurationException {
return getInstance(clazz.getName());
}
/**
* This method is supposed to clear all loggers.
* <p>
* In this implementation it calls a "stop" method if the logger factory supports it. This is the case of
* Logback.
* </p>
*/
@Override
public void release() {
final ILoggerFactory factory = LoggerFactory.getILoggerFactory();
try {
factory.getClass().getMethod("stop").invoke(factory);
} catch (final ReflectiveOperationException ignored) {
}
}
@Override
public void removeAttribute(final String name) {
attributes.remove(name);
}
@Override
public void setAttribute(final String name, final Object value) {
if (value != null) {
attributes.put(name, value);
} else {
removeAttribute(name);
}
}
private static class Slf4jLog implements Log {
private final Logger logger;
public Slf4jLog(final Logger logger) {
this.logger = logger;
}
@Override
public void debug(Object message) {
logger.debug(MARKER, String.valueOf(message));
}
@Override
public void debug(Object message, Throwable t) {
logger.debug(MARKER, String.valueOf(message), t);
}
@Override
public void error(Object message) {
logger.error(MARKER, String.valueOf(message));
}
@Override
public void error(Object message, Throwable t) {
logger.debug(MARKER, String.valueOf(message), t);
}
@Override
public void fatal(Object message) {
error(message);
}
@Override
public void fatal(Object message, Throwable t) {
error(message, t);
}
@Override
public void info(Object message) {
logger.info(MARKER, String.valueOf(message));
}
@Override
public void info(Object message, Throwable t) {
logger.info(MARKER, String.valueOf(message), t);
}
@Override
public boolean isDebugEnabled() {
return logger.isDebugEnabled(MARKER);
}
@Override
public boolean isErrorEnabled() {
return logger.isErrorEnabled(MARKER);
}
@Override
public boolean isFatalEnabled() {
return isErrorEnabled();
}
@Override
public boolean isInfoEnabled() {
return logger.isInfoEnabled(MARKER);
}
@Override
public boolean isTraceEnabled() {
return logger.isTraceEnabled(MARKER);
}
@Override
public boolean isWarnEnabled() {
return logger.isWarnEnabled(MARKER);
}
@Override
public void trace(Object message) {
logger.trace(MARKER, String.valueOf(message));
}
@Override
public void trace(Object message, Throwable t) {
logger.trace(MARKER, String.valueOf(message), t);
}
@Override
public void warn(Object message) {
logger.warn(MARKER, String.valueOf(message));
}
@Override
public void warn(Object message, Throwable t) {
logger.warn(MARKER, String.valueOf(message), t);
}
}
private static final class Slf4jLocationAwareLog implements Log {
private static final String FQCN = Slf4jLocationAwareLog.class.getName();
private final LocationAwareLogger logger;
public Slf4jLocationAwareLog(final LocationAwareLogger logger) {
this.logger = logger;
}
@Override
public void debug(Object message) {
log(DEBUG_INT, message, null);
}
@Override
public void debug(Object message, Throwable t) {
log(DEBUG_INT, message, t);
}
@Override
public void error(Object message) {
log(ERROR_INT, message, null);
}
@Override
public void error(Object message, Throwable t) {
log(ERROR_INT, message, t);
}
@Override
public void fatal(Object message) {
error(message);
}
@Override
public void fatal(Object message, Throwable t) {
error(message, t);
}
@Override
public void info(Object message) {
log(INFO_INT, message, null);
}
@Override
public void info(Object message, Throwable t) {
log(INFO_INT, message, t);
}
@Override
public boolean isDebugEnabled() {
return logger.isDebugEnabled(MARKER);
}
@Override
public boolean isErrorEnabled() {
return logger.isErrorEnabled(MARKER);
}
@Override
public boolean isFatalEnabled() {
return isErrorEnabled();
}
@Override
public boolean isInfoEnabled() {
return logger.isInfoEnabled(MARKER);
}
@Override
public boolean isTraceEnabled() {
return logger.isTraceEnabled(MARKER);
}
@Override
public boolean isWarnEnabled() {
return logger.isWarnEnabled(MARKER);
}
@Override
public void trace(Object message) {
log(TRACE_INT, message, null);
}
@Override
public void trace(Object message, Throwable t) {
log(TRACE_INT, message, t);
}
@Override
public void warn(Object message) {
log(WARN_INT, message, null);
}
@Override
public void warn(Object message, Throwable t) {
log(WARN_INT, message, t);
}
private void log(final int level, final Object message, final Throwable t) {
logger.log(MARKER, FQCN, level, String.valueOf(message), EMPTY_OBJECT_ARRAY, t);
}
}
}