Improved memory leak prevention for resource ResourceBundle

git-svn-id: https://svn.apache.org/repos/asf/tomcat/trunk@909097 13f79535-47bb-0310-9956-ffa450edef68

diff --git a/java/org/apache/catalina/loader/LocalStrings.properties b/java/org/apache/catalina/loader/LocalStrings.properties
index fe1dbac..b97b385 100644 (file)
--- a/java/org/apache/catalina/loader/LocalStrings.properties
+++ b/java/org/apache/catalina/loader/LocalStrings.properties
@@ -35,6 +35,8 @@ webappClassLoader.jdbcRemoveStreamError=Exception closing input stream during JD
 webappClassLoader.stopped=Illegal access: this web application instance has been stopped already.  Could not load {0}.  The eventual following stack trace is caused by an error thrown for debugging purposes as well as to attempt to terminate the thread which caused the illegal access, and has no functional impact.
 webappClassLoader.readError=Resource read error: Could not load {0}.
 webappClassLoader.clearJbdc=A web application registered the JBDC driver [{0}] but failed to unregister it when the web application was stopped. To prevent a memory leak, the JDBC Driver has been forcibly unregistered.
+webappClassLoader.clearReferencesResourceBundlesCount=Removed [{0}] ResourceBundle references from the cache
+webappClassLoader.clearReferencesResourceBundlesFail=Failed to clear ResourceBundle references
 webappClassLoader.clearRmiInfo=Failed to find class sun.rmi.transport.Target to clear context class loader. This is expected on non-Sun JVMs.
 webappClassLoader.clearRmiFail=Failed to clear context class loader referenced from sun.rmi.transport.Target 
 webappClassLoader.clearThreadLocalDebug=A web application created a ThreadLocal with key of type [{0}] (value [{1}]). The ThreadLocal has been correctly set to null and the key will be removed by GC. However, to simplify the process of tracing memory leaks, the key has been forcibly removed.

diff --git a/java/org/apache/catalina/loader/WebappClassLoader.java b/java/org/apache/catalina/loader/WebappClassLoader.java
index e9adf34..4aaa08c 100644 (file)
--- a/java/org/apache/catalina/loader/WebappClassLoader.java
+++ b/java/org/apache/catalina/loader/WebappClassLoader.java
@@ -25,6 +25,7 @@ import java.io.FilePermission;
 import java.io.IOException;
 import java.io.InputStream;
 import java.lang.ref.Reference;
+import java.lang.ref.WeakReference;
 import java.lang.reflect.Field;
 import java.lang.reflect.InvocationTargetException;
 import java.lang.reflect.Method;
@@ -47,6 +48,8 @@ import java.util.Iterator;
 import java.util.LinkedHashMap;
 import java.util.List;
 import java.util.Map;
+import java.util.ResourceBundle;
+import java.util.Set;
 import java.util.Vector;
 import java.util.concurrent.ThreadPoolExecutor;
 import java.util.jar.Attributes;
@@ -66,6 +69,7 @@ import org.apache.catalina.Lifecycle;
 import org.apache.catalina.LifecycleException;
 import org.apache.catalina.LifecycleListener;
 import org.apache.tomcat.util.res.StringManager;
+import org.apache.jasper.servlet.JasperLoader;
 import org.apache.naming.JndiPermission;
 import org.apache.naming.resources.Resource;
 import org.apache.naming.resources.ResourceAttributes;
@@ -1773,6 +1777,9 @@ public class WebappClassLoader
             org.apache.juli.logging.LogFactory.release(this);
         }
         
+        // Clear the resource bundle cache
+        clearReferencesResourceBundles();
+
         // Clear the classloader reference in the VM's bean introspector
         java.beans.Introspector.flushCaches();
 
@@ -2313,6 +2320,83 @@ public class WebappClassLoader
     
     
     /**
+     * Clear the {@link ResourceBundle} cache of any bundles loaded by this
+     * class loader or any class loader where this loader is a parent class
+     * loader. Whilst {@link ResourceBundle#clearCache()} could be used there
+     * are complications around the {@link JasperLoader} that mean a reflection
+     * based approach is more likely to be complete.
+     * 
+     * The ResourceBundle is using WeakReferences so it shouldn't be pinning the
+     * class loader in memory. However, it is. Therefore clear ou the
+     * references.
+     */
+    private void clearReferencesResourceBundles() {
+        // Get a reference to the cache
+        try {
+            Field cacheListField =
+                ResourceBundle.class.getDeclaredField("cacheList");
+            cacheListField.setAccessible(true);
+
+            // Java 6 uses ConcurrentMap
+            // Java 5 uses SoftCache extends Abstract Map
+            // So use Map and it *should* work with both
+            Map<?,?> cacheList = (Map<?,?>) cacheListField.get(null);
+            
+            // Get the keys (loader references are in the key)
+            Set<?> keys = cacheList.keySet();
+            
+            Field loaderRefField = null;
+            
+            // Iterate over the keys looking at the loader instances
+            Iterator<?> keysIter = keys.iterator();
+            
+            int countRemoved = 0;
+            
+            while (keysIter.hasNext()) {
+                Object key = keysIter.next();
+                
+                if (loaderRefField == null) {
+                    loaderRefField =
+                        key.getClass().getDeclaredField("loaderRef");
+                    loaderRefField.setAccessible(true);
+                }
+                WeakReference<?> loaderRef =
+                    (WeakReference<?>) loaderRefField.get(key);
+                
+                ClassLoader loader = (ClassLoader) loaderRef.get();
+                
+                while (loader != null && loader != this) {
+                    loader = loader.getParent();
+                }
+                
+                if (loader != null) {
+                    keysIter.remove();
+                    countRemoved++;
+                }
+            }
+            
+            if (countRemoved > 0 && log.isDebugEnabled()) {
+                log.debug(sm.getString(
+                        "webappClassLoader.clearReferencesResourceBundlesCount",
+                        Integer.valueOf(countRemoved)));
+            }
+        } catch (SecurityException e) {
+            log.error(sm.getString(
+                    "webappClassLoader.clearReferencesResourceBundlesFail"), e);
+        } catch (NoSuchFieldException e) {
+            log.error(sm.getString(
+                    "webappClassLoader.clearReferencesResourceBundlesFail"), e);
+        } catch (IllegalArgumentException e) {
+            log.error(sm.getString(
+                    "webappClassLoader.clearReferencesResourceBundlesFail"), e);
+        } catch (IllegalAccessException e) {
+            log.error(sm.getString(
+                    "webappClassLoader.clearReferencesResourceBundlesFail"), e);
+        }
+    }
+
+
+    /**
      * Determine whether a class was loaded by this class loader or one of
      * its child class loaders.
      */