/*

  * Copyright 2006-2011 The Kuali Foundation

  *

  * Licensed under the Educational Community 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.opensource.org/licenses/ecl2.php

  *

  * 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.kuali.rice.core.impl.resourceloader;

 import org.kuali.rice.core.api.util.ClassLoaderUtils;

 import org.kuali.rice.core.api.util.reflect.BaseTargetedInvocationHandler;

 import java.lang.reflect.InvocationTargetException;

 import java.lang.reflect.Method;

 import java.lang.reflect.Proxy;

 /**

  * A Proxy that sets the thread Context ClassLoader before invocation of the

  * proxied object, and resets it back afterwards.

  *

  * @author Kuali Rice Team (rice.collab@kuali.org)

  */

 public class ContextClassLoaderProxy extends BaseTargetedInvocationHandler {

     private static final org.apache.log4j.Logger LOG = org.apache.log4j.Logger.getLogger(ContextClassLoaderProxy.class);

     /**

      * Convenience method that wraps a specified object with a ContextClassLoaderProxy, with a specified

      * handler classloader and proxy classloader.  If the specified object is null, or the object classloader

      * equals the proxy classloader, the object is returned unwrapped.

      * @param proxiedObject the object to proxy

      * @param proxyClassLoader the classloader OF THE PROXY INSTANCE

      * @param objectClassLoader the classloader to set as the context classloader prior to any invocations on the proxiedObject

      * @return a ContextClassLoaderProxy Proxy for the proxiedObject

      */

     public static Object wrap(Object proxiedObject, Class<?>[] classesToProxy, ClassLoader proxyClassLoader, ClassLoader objectClassLoader) {

         if (proxiedObject == null) {

                 return null;

         }

             if (proxyClassLoader == null) {

             //proxyClassLoader = Thread.currentThread().getContextClassLoader();

                 proxyClassLoader = proxiedObject.getClass().getClassLoader();

         }

         if (objectClassLoader == null) {

             objectClassLoader = proxiedObject.getClass().getClassLoader();

         }

         if (classesToProxy == null) {

             classesToProxy = getInterfacesToProxy(proxyClassLoader, proxiedObject);

         }

         // this classloader comparison looks fishy

         // it is testing the classloader of the proxy against the intended *context* classloader of the proxiedObject

         // if these are the same the proxiedObject is not wrapped.  However, that implies that if the proxy

         // classloader may equal the intended context class loader, that the context class loader is actually not set,

         // and could theoretically NOT be the intended one in the future

         // somebody who understands this better than me should investigate this, and this method which I have

         // now applied to all prior uses of ContextClassLoaderProxy as a convenience

         //if (proxiedObject != null) { //&& !objectClassLoader.equals(proxyClassLoader)) {

         ContextClassLoaderProxy handler = new ContextClassLoaderProxy(objectClassLoader, proxiedObject);

         LOG.debug("Installed a ContextClassLoaderProxy on object: " + proxiedObject.getClass().getName());

         proxiedObject = Proxy.newProxyInstance(proxyClassLoader, classesToProxy, handler);

         //}

         return proxiedObject;

     }

     public static Object wrap(Object proxiedObject, ClassLoader proxyClassLoader, ClassLoader objectClassLoader) {

             return wrap(proxiedObject, null, proxyClassLoader, objectClassLoader);

     }

     public static Object wrap(Object proxiedObject, ClassLoader classLoader) {

             return wrap(proxiedObject, classLoader, classLoader);

     }

     public static Object wrap(Object proxiedObject, Class<?>[] classesToProxy) {

             return wrap(proxiedObject, classesToProxy, null, null);

     }

     public static Object wrap(Object proxiedObject, Class<?>[] classesToProxy, ClassLoader classLoader) {

             return wrap(proxiedObject, classesToProxy, classLoader, classLoader);

     }

     public static Object wrap(Object proxiedObject) {

             return wrap(proxiedObject, null, null, null);

     }

     public static Class<?>[] getInterfacesToProxy(Object proxiedObject) {

         return getInterfacesToProxy(null, proxiedObject);

     }

     /**

      * Determines the interfaces which need to be proxied and are visable to the given proxy ClassLoader.

      */

     public static Class<?>[] getInterfacesToProxy(ClassLoader proxyClassLoader, Object proxiedObject) {

             return ClassLoaderUtils.getInterfacesToProxy(proxiedObject, proxyClassLoader, null);

     }

     private ClassLoader classLoader;

     public ContextClassLoaderProxy(ClassLoader classLoader, Object target) {

             super(target);

         this.classLoader = classLoader;

     }

     protected Object invokeInternal(Object proxy, Method m, Object[] args) throws Throwable {

         ClassLoader oldCl = Thread.currentThread().getContextClassLoader();

         try {

             Thread.currentThread().setContextClassLoader(this.classLoader);

             return m.invoke(getTarget(), args);

         } catch (InvocationTargetException e) {

                 throw (e.getCause() != null ? e.getCause() : e);

         } finally {

             Thread.currentThread().setContextClassLoader(oldCl);

         }

     }

 }