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/**
 *  Copyright 2003-2010 Terracotta, Inc.
 *
 *  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 net.sf.ehcache.exceptionhandler;

import net.sf.ehcache.Ehcache;

import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;


/**
 * A dynamic proxy which provides CacheException handling.
 * 

* The ehcache configuration will create and register in the CacheManager {@link Ehcache}s decorated * with this dynamic proxy. See following for programmatic use. *

* The createProxy factory method may be used to simply create a proxy. Otherwise the calling client * will need code similar to: *

 * (Ehcache) Proxy.newProxyInstance(ehcache.getClass().getClassLoader(), new Class[]{ Ehcache.class },
 * new ExceptionHandlingDynamicCacheProxy(ehcache));
*

* A common usage is to create a proxy and then register the proxy in CacheManager in place of the * underlying cache. To do that create a proxy and then call *

 * cacheManager.replaceCacheWithDecoratedCache(Ehcache cache, Ehcache decoratedCache);
 * 
* All clients accessing the cache throughcacheManager.getEhcache() will then receive proxy references. *

* See CacheTest for a perf test. * * @author Greg Luck * @version $Id: ExceptionHandlingDynamicCacheProxy.java 2154 2010-04-06 02:45:52Z cdennis $ */ public final class ExceptionHandlingDynamicCacheProxy implements InvocationHandler { private static final Logger LOG = LoggerFactory.getLogger(ExceptionHandlingDynamicCacheProxy.class.getName()); private Ehcache ehcache; /** * Constructor: Use with something like: *

     * (Ehcache) Proxy.newProxyInstance(ehcache.getClass().getClassLoader(), new Class[]{ Ehcache.class },
     * new ExceptionHandlingDynamicCacheProxy(ehcache));
* @param ehcache the backing ehcache */ public ExceptionHandlingDynamicCacheProxy(Ehcache ehcache) { this.ehcache = ehcache; } /** * A simple factory method to hide the messiness of creating the proxy from clients. * * @param ehcache the target cache * @return a proxied Ehcache */ public static Ehcache createProxy(Ehcache ehcache) { return (Ehcache) Proxy.newProxyInstance(ehcache.getClass().getClassLoader(), new Class[]{Ehcache.class}, new ExceptionHandlingDynamicCacheProxy(ehcache)); } /** * Processes a method invocation on a proxy instance and returns * the result. This method will be invoked on an invocation handler * when a method is invoked on a proxy instance that it is * associated with. * * @param proxy the proxy instance that the method was invoked on * @param method the Method instance corresponding to * the interface method invoked on the proxy instance. The declaring * class of the Method object will be the interface that * the method was declared in, which may be a superinterface of the * proxy interface that the proxy class inherits the method through. * @param args an array of objects containing the values of the * arguments passed in the method invocation on the proxy instance, * or null if interface method takes no arguments. * Arguments of primitive types are wrapped in instances of the * appropriate primitive wrapper class, such as * java.lang.Integer or java.lang.Boolean. * @return the value to return from the method invocation on the * proxy instance. If the declared return type of the interface * method is a primitive type, then the value returned by * this method must be an instance of the corresponding primitive * wrapper class; otherwise, it must be a type assignable to the * declared return type. If the value returned by this method is * null and the interface method's return type is * primitive, then a NullPointerException will be * thrown by the method invocation on the proxy instance. If the * value returned by this method is otherwise not compatible with * the interface method's declared return type as described above, * a ClassCastException will be thrown by the method * invocation on the proxy instance. * @throws Throwable the exception to throw from the method * invocation on the proxy instance. The exception's type must be * assignable either to any of the exception types declared in the * throws clause of the interface method or to the * unchecked exception types java.lang.RuntimeException * or java.lang.Error. If a checked exception is * thrown by this method that is not assignable to any of the * exception types declared in the throws clause of * the interface method, then an * {@link java.lang.reflect.UndeclaredThrowableException} containing the * exception that was thrown by this method will be thrown by the * method invocation on the proxy instance. * @see java.lang.reflect.UndeclaredThrowableException * */ public Object invoke(Object proxy, Method method, Object[] args) throws Throwable { Object invocationResult = null; try { invocationResult = method.invoke(ehcache, args); } catch (Exception e) { CacheExceptionHandler cacheExceptionHandler = ehcache.getCacheExceptionHandler(); if (cacheExceptionHandler != null) { String keyAsString = null; //should be a CacheException Throwable cause = e.getCause(); if (cause != null) { keyAsString = extractKey(cause.getMessage()); } Exception causeAsException = null; try { causeAsException = (Exception) cause; } catch (ClassCastException cce) { //we only handle exceptions, not errors. LOG.debug("Underlying cause was not an Exception: {}", cce); } cacheExceptionHandler.onException(ehcache, keyAsString, causeAsException); } else { throw e.getCause(); } } return invocationResult; } /** * Extracts the key from the message, if any */ static String extractKey(String message) { if (message == null) { return null; } int beginIndex = message.lastIndexOf("key "); if (beginIndex < 0) { return null; } beginIndex += "key ".length(); int endIndex = beginIndex; for (int i = beginIndex; i < message.length(); i++) { char character = message.charAt(i); if (character == ' ') { break; } endIndex = i; } endIndex++; if (endIndex > message.length()) { endIndex = message.length(); } String key = message.substring(beginIndex, endIndex); return key; } }




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