[LOGGING-192] Fix factory loading from TCCL (#281)

This fixes the loading of standard `LogFactory` implementations from the TCCL.

The current code has a fallback clause in `newFactory`, so it can happen that the code tests for the presence of Log4j API and SLF4J in the TCCL, but it actually loads the factory from the current classloader (which lacks either of those libraries).

src/test/java/org/apache/commons/logging/security/SecurityForbiddenTestCase.java

@@ -22,6 +22,7 @@ import static org.junit.Assert.assertNotEquals;
 import java.io.PrintWriter;
 import java.io.StringWriter;
 import java.lang.reflect.Field;
+import java.lang.reflect.InvocationTargetException;
 import java.lang.reflect.Method;
 import java.util.Hashtable;
 
@@ -93,10 +94,11 @@ public class SecurityForbiddenTestCase extends TestCase {
             final Class<?> clazz = classLoader.loadClass(name);
             return clazz.getConstructor().newInstance();
         } catch (final Exception e) {
+            final Throwable wrapped = e instanceof InvocationTargetException ? ((InvocationTargetException) e).getTargetException() : e;
             final StringWriter sw = new StringWriter();
             final PrintWriter pw = new PrintWriter(sw);
-            e.printStackTrace(pw);
-            fail("Unexpected exception:" + e.getMessage() + ":" + sw.toString());
+            wrapped.printStackTrace(pw);
+            fail("Unexpected exception:" + wrapped.getMessage() + ":" + sw);
         }
         return null;
     }

src/test/java/org/apache/commons/logging/tccl/logfactory/AdaptersTcclTestCase.java

@@ -0,0 +1,76 @@
+/*
+ * 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.tccl.logfactory;
+
+import junit.framework.Test;
+import junit.framework.TestCase;
+import org.apache.commons.logging.LogFactory;
+import org.apache.commons.logging.PathableClassLoader;
+import org.apache.commons.logging.PathableTestSuite;
+import org.apache.commons.logging.impl.Log4jApiLogFactory;
+
+/**
+ * Verifies that if the TCCL contains only `commons-logging-adapters`, it can load a web-application specific
+ * logging backend.
+ */
+public class AdaptersTcclTestCase extends TestCase {
+
+    /**
+     * Return the tests included in this test suite.
+     */
+    public static Test suite() throws Exception {
+        // The classloader running the test has access to `commons-logging`
+        final PathableClassLoader classLoader = new PathableClassLoader(null);
+        classLoader.useExplicitLoader("junit.", Test.class.getClassLoader());
+        classLoader.addLogicalLib("commons-logging");
+        classLoader.addLogicalLib("testclasses");
+
+        // The TCCL has access to both `commons-logging-adapters` and `log4j-api`
+        final PathableClassLoader tcclLoader = new PathableClassLoader(classLoader);
+        tcclLoader.addLogicalLib("commons-logging-adapters");
+        tcclLoader.addLogicalLib("log4j-api");
+        tcclLoader.setParentFirst(false);
+
+        final Class<?> testClass = classLoader.loadClass(AdaptersTcclTestCase.class.getName());
+        return new PathableTestSuite(testClass, tcclLoader);
+    }
+
+    /**
+     * Sets up instance variables required by this test case.
+     */
+    @Override
+    public void setUp() throws Exception {
+        LogFactory.releaseAll();
+    }
+
+    /**
+     * Tear down instance variables required by this test case.
+     */
+    @Override
+    public void tearDown() {
+        LogFactory.releaseAll();
+    }
+
+    public void testFactoryLoading() {
+        final LogFactory factory = LogFactory.getFactory();
+        // The implementation comes from the TCCL
+        assertEquals(Thread.currentThread().getContextClassLoader(), factory.getClass().getClassLoader());
+        // It uses the `log4j-api` only available in the TCCL
+        assertEquals(Log4jApiLogFactory.class.getName(), factory.getClass().getName());
+    }
+}

src/test/java/org/apache/commons/logging/tccl/logfactory/SiblingTcclTestCase.java

@@ -0,0 +1,72 @@
+/*
+ * 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.tccl.logfactory;
+
+import junit.framework.Test;
+import junit.framework.TestCase;
+import org.apache.commons.logging.LogFactory;
+import org.apache.commons.logging.PathableClassLoader;
+import org.apache.commons.logging.PathableTestSuite;
+
+/**
+ * Verifies that if the TCCL is a sibling of the classloader with `commons-logging`
+ */
+public class SiblingTcclTestCase extends TestCase {
+
+    /**
+     * Return the tests included in this test suite.
+     */
+    public static Test suite() throws Exception {
+        // The classloader running the test has access to `commons-logging`
+        final PathableClassLoader classLoader = new PathableClassLoader(null);
+        classLoader.useExplicitLoader("junit.", Test.class.getClassLoader());
+        classLoader.addLogicalLib("commons-logging");
+        classLoader.addLogicalLib("testclasses");
+
+        // The TCCL has only access to `log4j-api` and `slf4j-api`
+        // See https://issues.apache.org/jira/browse/LOGGING-192
+        final PathableClassLoader tcclLoader = new PathableClassLoader(null);
+        tcclLoader.addLogicalLib("log4j-api");
+
+        final Class<?> testClass = classLoader.loadClass(SiblingTcclTestCase.class.getName());
+        return new PathableTestSuite(testClass, tcclLoader);
+    }
+
+    /**
+     * Sets up instance variables required by this test case.
+     */
+    @Override
+    public void setUp() throws Exception {
+        LogFactory.releaseAll();
+    }
+
+    /**
+     * Tear down instance variables required by this test case.
+     */
+    @Override
+    public void tearDown() {
+        LogFactory.releaseAll();
+    }
+
+    public void testFactoryLoading() {
+        // Loading the factory does not fail as in LOGGING-192
+        final LogFactory factory = LogFactory.getFactory();
+        // The selected implementation comes from this classloader
+        assertEquals(getClass().getClassLoader(), factory.getClass().getClassLoader());
+    }
+}