src/main/java/org/apache/commons/proxy/factory/cglib/CglibProxyFactory.java

/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You 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 org.apache.commons.proxy.factory.cglib;

import net.sf.cglib.proxy.Callback;
import net.sf.cglib.proxy.CallbackFilter;
import net.sf.cglib.proxy.Dispatcher;
import net.sf.cglib.proxy.Enhancer;
import net.sf.cglib.proxy.MethodProxy;
import net.sf.cglib.proxy.MethodInterceptor;
import org.apache.commons.proxy.Interceptor;
import org.apache.commons.proxy.Invocation;
import org.apache.commons.proxy.Invoker;
import org.apache.commons.proxy.ObjectProvider;
import org.apache.commons.proxy.factory.util.AbstractSubclassingProxyFactory;

import java.io.Serializable;
import java.lang.reflect.Method;

/**
 * A <a href="http://cglib.sourceforge.net/">CGLIB</a>-based {@link org.apache.commons.proxy.ProxyFactory}
 * implementation.
 * <p/>
 * <p/>
 * <b>Dependencies</b>: <ul> <li>CGLIB version 2.0.2 or greater</li> </ul> </p>
 *
 * @author James Carman
 * @since 1.0
 */
public class CglibProxyFactory extends AbstractSubclassingProxyFactory
{
//**********************************************************************************************************************
// Fields
//**********************************************************************************************************************

    private static CallbackFilter callbackFilter = new CglibProxyFactoryCallbackFilter();

//**********************************************************************************************************************
// Other Methods
//**********************************************************************************************************************

    public Object createDelegatorProxy(ClassLoader classLoader, ObjectProvider targetProvider,
                                       Class[] proxyClasses)
    {
        final Enhancer enhancer = new Enhancer();
        enhancer.setClassLoader(classLoader);
        enhancer.setInterfaces(toInterfaces(proxyClasses));
        enhancer.setSuperclass(getSuperclass(proxyClasses));
        enhancer.setCallbackFilter(callbackFilter);
        enhancer.setCallbacks(new Callback[]{new ObjectProviderDispatcher(targetProvider), new EqualsHandler(), new HashCodeHandler()});
        return enhancer.create();
    }

    public Object createInterceptorProxy(ClassLoader classLoader, Object target, Interceptor interceptor,
                                         Class[] proxyClasses)
    {
        final Enhancer enhancer = new Enhancer();
        enhancer.setClassLoader(classLoader);
        enhancer.setInterfaces(toInterfaces(proxyClasses));
        enhancer.setSuperclass(getSuperclass(proxyClasses));
        enhancer.setCallbackFilter(callbackFilter);
        enhancer.setCallbacks(new Callback[]{new InterceptorBridge(target, interceptor), new EqualsHandler(), new HashCodeHandler()});
        return enhancer.create();
    }

    public Object createInvokerProxy(ClassLoader classLoader, Invoker invoker,
                                     Class[] proxyClasses)
    {
        final Enhancer enhancer = new Enhancer();
        enhancer.setClassLoader(classLoader);
        enhancer.setInterfaces(toInterfaces(proxyClasses));
        enhancer.setSuperclass(getSuperclass(proxyClasses));
        enhancer.setCallbackFilter(callbackFilter);
        enhancer.setCallbacks(new Callback[]{new InvokerBridge(invoker), new EqualsHandler(), new HashCodeHandler()});
        return enhancer.create();
    }

//**********************************************************************************************************************
// Inner Classes
//**********************************************************************************************************************

    private static class InterceptorBridge implements net.sf.cglib.proxy.MethodInterceptor, Serializable
    {
        private final Interceptor inner;
        private final Object target;

        public InterceptorBridge(Object target, Interceptor inner)
        {
            this.inner = inner;
            this.target = target;
        }

        public Object intercept(Object object, Method method, Object[] args, MethodProxy methodProxy) throws Throwable
        {
            return inner.intercept(new MethodProxyInvocation(target, method, args, methodProxy));
        }
    }

    private static class HashCodeHandler implements MethodInterceptor, Serializable
    {
        public Object intercept(Object o, Method method, Object[] objects, MethodProxy methodProxy) throws Throwable
        {
            return new Integer(System.identityHashCode(o));
        }
    }

    private static class EqualsHandler implements MethodInterceptor, Serializable
    {
        public Object intercept(Object o, Method method, Object[] objects, MethodProxy methodProxy) throws Throwable
        {
            return Boolean.valueOf(o == objects[0]);
        }
    }


    private static class InvokerBridge implements net.sf.cglib.proxy.InvocationHandler, Serializable
    {
        private final Invoker original;

        public InvokerBridge(Invoker original)
        {
            this.original = original;
        }

        public Object invoke(Object object, Method method, Object[] objects) throws Throwable
        {
            return original.invoke(object, method, objects);
        }
    }

    private static class MethodProxyInvocation implements Invocation, Serializable
    {
        private final MethodProxy methodProxy;
        private final Method method;
        private final Object[] args;
        private final Object target;

        public MethodProxyInvocation(Object target, Method method, Object[] args, MethodProxy methodProxy)
        {
            this.target = target;
            this.method = method;
            this.methodProxy = methodProxy;
            this.args = args;
        }

        public Method getMethod()
        {
            return method;
        }

        public Object[] getArguments()
        {
            return args;
        }

        public Object proceed() throws Throwable
        {
            return methodProxy.invoke(target, args);
        }

        public Object getProxy()
        {
            return target;
        }
    }

    private static class ObjectProviderDispatcher implements Dispatcher, Serializable
    {
        private final ObjectProvider delegateProvider;

        public ObjectProviderDispatcher(ObjectProvider delegateProvider)
        {
            this.delegateProvider = delegateProvider;
        }

        public Object loadObject()
        {
            return delegateProvider.getObject();
        }
    }

    private static class CglibProxyFactoryCallbackFilter implements CallbackFilter
    {
        public int accept(Method method)
        {
            if (isEqualsMethod(method))
            {
                return 1;
            }
            else if (isHashCode(method))
            {
                return 2;
            }
            else
            {
                return 0;
            }
        }


    }
}