001 /** 002 * Licensed to the Apache Software Foundation (ASF) under one or more 003 * contributor license agreements. See the NOTICE file distributed with 004 * this work for additional information regarding copyright ownership. 005 * The ASF licenses this file to You under the Apache License, Version 2.0 006 * (the "License"); you may not use this file except in compliance with 007 * the License. You may obtain a copy of the License at 008 * 009 * http://www.apache.org/licenses/LICENSE-2.0 010 * 011 * Unless required by applicable law or agreed to in writing, software 012 * distributed under the License is distributed on an "AS IS" BASIS, 013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 014 * See the License for the specific language governing permissions and 015 * limitations under the License. 016 */ 017 package org.apache.xbean.classloader; 018 019 import java.util.Map; 020 import java.lang.reflect.Field; 021 import java.lang.reflect.Method; 022 import java.beans.Introspector; 023 import java.io.ObjectInputStream; 024 import java.io.ObjectOutputStream; 025 import java.io.ObjectStreamClass; 026 027 /** 028 * Utility methods for class loader manipulation in a server environment. 029 * 030 * @author Dain Sundstrom 031 * @version $Id: ClassLoaderUtil.java 813161 2009-09-09 23:03:32Z djencks $ 032 * @since 2.0 033 */ 034 public final class ClassLoaderUtil { 035 private ClassLoaderUtil() { 036 } 037 038 /** 039 * Cleans well known class loader leaks in VMs and libraries. There is a lot of bad code out there and this method 040 * will clear up the known problems. This method should only be called when the class loader will no longer be used. 041 * It this method is called two often it can have a serious impact on preformance. 042 * @param classLoader the class loader to destroy 043 */ 044 public static void destroy(ClassLoader classLoader) { 045 releaseCommonsLoggingCache(classLoader); 046 clearSunSoftCache(ObjectInputStream.class, "subclassAudits"); 047 clearSunSoftCache(ObjectOutputStream.class, "subclassAudits"); 048 clearSunSoftCache(ObjectStreamClass.class, "localDescs"); 049 clearSunSoftCache(ObjectStreamClass.class, "reflectors"); 050 Introspector.flushCaches(); 051 } 052 053 /** 054 * Clears the caches maintained by the SunVM object stream implementation. This method uses reflection and 055 * setAccessable to obtain access to the Sun cache. The cache is locked with a synchronize monitor and cleared. 056 * This method completely clears the class loader cache which will impact performance of object serialization. 057 * @param clazz the name of the class containing the cache field 058 * @param fieldName the name of the cache field 059 */ 060 public static void clearSunSoftCache(Class clazz, String fieldName) { 061 Map cache = null; 062 try { 063 Field field = clazz.getDeclaredField(fieldName); 064 field.setAccessible(true); 065 cache = (Map) field.get(null); 066 } catch (Throwable ignored) { 067 // there is nothing a user could do about this anyway 068 } 069 070 if (cache != null) { 071 synchronized (cache) { 072 cache.clear(); 073 } 074 } 075 } 076 077 /** 078 * Releases the specified classloader from the Apache Jakarta Commons Logging class loader cache using reflection. 079 * @param classLoader the class loader to release 080 */ 081 public static void releaseCommonsLoggingCache(ClassLoader classLoader) { 082 try { 083 Class logFactory = classLoader.loadClass("org.apache.commons.logging.LogFactory"); 084 Method release = logFactory.getMethod("release", new Class[] {ClassLoader.class}); 085 release.invoke(null, new Object[] {classLoader}); 086 } catch (Throwable ignored) { 087 // there is nothing a user could do about this anyway 088 } 089 } 090 091 }