Creates a parallel-capable classloader

Closes #46.
copernik-eu · Aug 18, 2023 · 596159d · 596159d
1 parent 58ddd35
commit 596159d
Show file tree

Hide file tree

Showing 4 changed files with 145 additions and 23 deletions.
diff --git a/log4j-tomcat/src/main/java/eu/copernik/log4j/tomcat/ClassLoaderUtil.java b/log4j-tomcat/src/main/java/eu/copernik/log4j/tomcat/ClassLoaderUtil.java
@@ -0,0 +1,44 @@
+/*
+ * Copyright © 2022 Piotr P. Karwasz
+ *
+ * Licensed 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 eu.copernik.log4j.tomcat;
+
+class ClassLoaderUtil {
+
+  static boolean isLog4jApiResource(final String name, final boolean isClassName) {
+    if (isClassName && name.startsWith("org.apache.logging.log4j.")) {
+      if (name.indexOf('.', 25) == -1
+          || name.startsWith("internal.", 25)
+          || name.startsWith("message.", 25)
+          || name.startsWith("simple.", 25)
+          || name.startsWith("spi.", 25)
+          || name.startsWith("status.", 25)
+          || name.startsWith("util.", 25)) {
+        return true;
+      }
+    } else if (!isClassName && name.startsWith("org/apache/logging/log4j/")) {
+      if (name.indexOf('/', 25) == -1
+          || name.startsWith("internal/", 25)
+          || name.startsWith("message/", 25)
+          || name.startsWith("simple/", 25)
+          || name.startsWith("spi/", 25)
+          || name.startsWith("status/", 25)
+          || name.startsWith("util/", 25)) {
+        return true;
+      }
+    }
+    return false;
+  }
+}
diff --git a/log4j-tomcat/src/main/java/eu/copernik/log4j/tomcat/Log4jParallelWebappClassLoader.java b/log4j-tomcat/src/main/java/eu/copernik/log4j/tomcat/Log4jParallelWebappClassLoader.java
@@ -0,0 +1,76 @@
+/*
+ * Copyright © 2022 Piotr P. Karwasz
+ *
+ * Licensed 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 eu.copernik.log4j.tomcat;
+
+import org.apache.catalina.LifecycleException;
+import org.apache.catalina.loader.ParallelWebappClassLoader;
+
+/**
+ * A classloader that delegates lookups for Log4j2 API classes to the parent classloader.
+ *
+ * <p>This allows multiple applications bundled with Log4j2 API to use a single copy of Log4j2 in
+ * the parent classloader, without modifying the servlet delegation model for the application.
+ *
+ * <p>In order to replace the default application classloader add:
+ *
+ * <pre>
+ * &lt;Context&gt;
+ *     ...
+ *     &lt;Loader loaderClass="eu.copernik.log4j.tomcat.Log4jParallelWebappClassLoader"/&gt;
+ * &lt;/Context&gt;
+ * </pre>
+ *
+ * <p>to the application's context definition (cf. <a href=
+ * "https://tomcat.apache.org/tomcat-10.0-doc/config/context.html#Defining_a_context">defining a
+ * context</a>).
+ */
+public class Log4jParallelWebappClassLoader extends ParallelWebappClassLoader {
+
+  public Log4jParallelWebappClassLoader() {
+    super();
+  }
+
+  public Log4jParallelWebappClassLoader(ClassLoader parent) {
+    super(parent);
+  }
+
+  @Override
+  protected boolean filter(String name, boolean isClassName) {
+    if (name == null || name.length() < 25) {
+      return super.filter(name, isClassName);
+    }
+    if (ClassLoaderUtil.isLog4jApiResource(name, isClassName)) {
+      return true;
+    }
+    return super.filter(name, isClassName);
+  }
+
+  @Override
+  public Log4jParallelWebappClassLoader copyWithoutTransformers() {
+
+    Log4jParallelWebappClassLoader result = new Log4jParallelWebappClassLoader(getParent());
+
+    super.copyStateWithoutTransformers(result);
+
+    try {
+      result.start();
+    } catch (LifecycleException e) {
+      throw new IllegalStateException(e);
+    }
+
+    return result;
+  }
+}
diff --git a/log4j-tomcat/src/main/java/eu/copernik/log4j/tomcat/Log4jWebappClassLoader.java b/log4j-tomcat/src/main/java/eu/copernik/log4j/tomcat/Log4jWebappClassLoader.java
@@ -16,7 +16,7 @@
 package eu.copernik.log4j.tomcat;
 
 import org.apache.catalina.LifecycleException;
-import org.apache.catalina.loader.WebappClassLoaderBase;
+import org.apache.catalina.loader.WebappClassLoader;
 
 /**
  * A classloader that delegates lookups for Log4j2 API classes to the parent classloader.
@@ -29,15 +29,15 @@
  * <pre>
  * &lt;Context&gt;
  *     ...
- *     &lt;Loader loaderClass="eu.copernik.log4j.tomcat.Log4jWebappClassLoader"/&gt;
+ *     &lt;Loader loaderClass="eu.copernik.log4j.tomcat.Log4jParallelWebappClassLoader"/&gt;
  * &lt;/Context&gt;
  * </pre>
  *
  * <p>to the application's context definition (cf. <a href=
  * "https://tomcat.apache.org/tomcat-10.0-doc/config/context.html#Defining_a_context">defining a
  * context</a>).
  */
-public class Log4jWebappClassLoader extends WebappClassLoaderBase {
+public class Log4jWebappClassLoader extends WebappClassLoader {
 
   public Log4jWebappClassLoader() {
     super();
@@ -52,26 +52,8 @@ protected boolean filter(String name, boolean isClassName) {
     if (name == null || name.length() < 25) {
       return super.filter(name, isClassName);
     }
-    if (isClassName && name.startsWith("org.apache.logging.log4j.")) {
-      if (name.indexOf('.', 25) == -1
-          || name.startsWith("internal.", 25)
-          || name.startsWith("message.", 25)
-          || name.startsWith("simple.", 25)
-          || name.startsWith("spi.", 25)
-          || name.startsWith("status.", 25)
-          || name.startsWith("util.", 25)) {
-        return true;
-      }
-    } else if (!isClassName && name.startsWith("org/apache/logging/log4j/")) {
-      if (name.indexOf('/', 25) == -1
-          || name.startsWith("internal/", 25)
-          || name.startsWith("message/", 25)
-          || name.startsWith("simple/", 25)
-          || name.startsWith("spi/", 25)
-          || name.startsWith("status/", 25)
-          || name.startsWith("util/", 25)) {
-        return true;
-      }
+    if (ClassLoaderUtil.isLog4jApiResource(name, isClassName)) {
+      return true;
     }
     return super.filter(name, isClassName);
   }

diff --git a/log4j-tomcat/src/test/java/eu/copernik/log4j/tomcat/Log4jWebappClassLoaderTest.java b/log4j-tomcat/src/test/java/eu/copernik/log4j/tomcat/Log4jWebappClassLoaderTest.java
@@ -140,4 +140,24 @@ public void testLog4jClassloader() throws IOException {
               });
     }
   }
+
+  @RepeatedTest(100)
+  public void testParallelLog4jClassloader() throws IOException {
+    try (final URLClassLoader cl = createClassLoader(Log4jParallelWebappClassLoader.class); ) {
+      classes()
+          .forEach(
+              arg -> {
+                final Class<?> clazz = (Class<?>) arg.get()[0];
+                final boolean isEqual = (boolean) arg.get()[1];
+                final Class<?> otherClazz =
+                    assertDoesNotThrow(() -> Class.forName(clazz.getName(), true, cl));
+                final ClassAssert assertion = assertThat(otherClazz);
+                if (isEqual) {
+                  assertion.isEqualTo(clazz);
+                } else {
+                  assertion.isNotEqualTo(clazz);
+                }
+              });
+    }
+  }
 }