jdk/src/main/java/org/apache/commons/proxy2/jdk/JdkProxyFactory.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.proxy2.jdk;

import java.io.Serializable;
import java.lang.reflect.InvocationHandler;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;

import org.apache.commons.lang3.ArrayUtils;
import org.apache.commons.lang3.ObjectUtils;
import org.apache.commons.proxy2.Interceptor;
import org.apache.commons.proxy2.Invocation;
import org.apache.commons.proxy2.Invoker;
import org.apache.commons.proxy2.ObjectProvider;
import org.apache.commons.proxy2.ProxyUtils;
import org.apache.commons.proxy2.impl.AbstractProxyFactory;

/**
 * {@link org.apache.commons.proxy2.ProxyFactory ProxyFactory} implementation that uses {@link java.lang.reflect.Proxy}
 * proxies.
 */
public class JdkProxyFactory extends AbstractProxyFactory
{
    //******************************************************************************************************************
    // ProxyFactory Implementation
    //******************************************************************************************************************

    /**
     * Creates a proxy2 which delegates to the object provided by <code>delegateProvider</code>.
     * 
     * @param classLoader
     *            the class loader to use when generating the proxy2
     * @param delegateProvider
     *            the delegate provider
     * @param proxyClasses
     *            the interfaces that the proxy2 should implement
     * @return a proxy2 which delegates to the object provided by the target <code>delegateProvider>
     */
    @Override
    public <T> T createDelegatorProxy(ClassLoader classLoader, ObjectProvider<?> delegateProvider,
            Class<?>... proxyClasses)
    {
        @SuppressWarnings("unchecked") // type inference
        final T result = (T) Proxy.newProxyInstance(classLoader, proxyClasses, new DelegatorInvocationHandler(
                delegateProvider));
        return result;
    }

    /**
     * Creates a proxy2 which passes through a {@link Interceptor interceptor} before eventually reaching the
     * <code>target</code> object.
     * 
     * @param classLoader
     *            the class loader to use when generating the proxy2
     * @param target
     *            the target object
     * @param interceptor
     *            the method interceptor
     * @param proxyClasses
     *            the interfaces that the proxy2 should implement.
     * @return a proxy2 which passes through a {@link Interceptor interceptor} before eventually reaching the
     *         <code>target</code> object.
     */
    @Override
    public <T> T createInterceptorProxy(ClassLoader classLoader, Object target, Interceptor interceptor,
            Class<?>... proxyClasses)
    {
        @SuppressWarnings("unchecked") // type inference
        final T result = (T) Proxy.newProxyInstance(classLoader, proxyClasses, new InterceptorInvocationHandler(target,
                interceptor));
        return result;
    }

    /**
     * Creates a proxy2 which uses the provided {@link Invoker} to handle all method invocations.
     * 
     * @param classLoader
     *            the class loader to use when generating the proxy2
     * @param invoker
     *            the invoker
     * @param proxyClasses
     *            the interfaces that the proxy2 should implement
     * @return a proxy2 which uses the provided {@link Invoker} to handle all method invocations
     */
    @Override
    public <T> T createInvokerProxy(ClassLoader classLoader, Invoker invoker, Class<?>... proxyClasses)
    {
        @SuppressWarnings("unchecked") // type inference
        final T result = (T) Proxy.newProxyInstance(classLoader, proxyClasses, new InvokerInvocationHandler(invoker));
        return result;
    }

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

    private abstract static class AbstractInvocationHandler implements InvocationHandler, Serializable
    {
        /** Serialization version */
        private static final long serialVersionUID = 1L;

        @Override
        public Object invoke(Object proxy, Method method, Object[] args) throws Throwable
        {
            if (ProxyUtils.isHashCode(method))
            {
                return Integer.valueOf(System.identityHashCode(proxy));
            }
            else if (ProxyUtils.isEqualsMethod(method))
            {
                return Boolean.valueOf(proxy == args[0]);
            }
            else
            {
                return invokeImpl(proxy, method, args);
            }
        }

        protected abstract Object invokeImpl(Object proxy, Method method, Object[] args) throws Throwable;
    }

    private static class DelegatorInvocationHandler extends AbstractInvocationHandler
    {
        /** Serialization version */
        private static final long serialVersionUID = 1L;

        private final ObjectProvider<?> delegateProvider;

        protected DelegatorInvocationHandler(ObjectProvider<?> delegateProvider)
        {
            this.delegateProvider = delegateProvider;
        }

        @Override
        public Object invokeImpl(Object proxy, Method method, Object[] args) throws Throwable
        {
            try
            {
                return method.invoke(delegateProvider.getObject(), args);
            }
            catch (InvocationTargetException e)
            {
                throw e.getTargetException();
            }
        }
    }

    private static class InterceptorInvocationHandler extends AbstractInvocationHandler
    {
        /** Serialization version */
        private static final long serialVersionUID = 1L;

        private final Object target;
        private final Interceptor methodInterceptor;

        public InterceptorInvocationHandler(Object target, Interceptor methodInterceptor)
        {
            this.target = target;
            this.methodInterceptor = methodInterceptor;
        }

        @Override
        public Object invokeImpl(Object proxy, Method method, Object[] args) throws Throwable
        {
            final ReflectionInvocation invocation = new ReflectionInvocation(proxy, target, method, args);
            return methodInterceptor.intercept(invocation);
        }
    }

    private static class InvokerInvocationHandler extends AbstractInvocationHandler
    {
        /** Serialization version */
        private static final long serialVersionUID = 1L;

        private final Invoker invoker;

        public InvokerInvocationHandler(Invoker invoker)
        {
            this.invoker = invoker;
        }

        @Override
        public Object invokeImpl(Object proxy, Method method, Object[] args) throws Throwable
        {
            return invoker.invoke(proxy, method, args);
        }
    }

    private static class ReflectionInvocation implements Invocation
    {
        private final Object proxy;
        private final Object target;
        private final Method method;
        private final Object[] arguments;

        public ReflectionInvocation(Object proxy, Object target, Method method, Object[] arguments)
        {
            this.proxy = proxy;
            this.target = target;
            this.method = method;
            this.arguments = ObjectUtils.defaultIfNull(ArrayUtils.clone(arguments), ProxyUtils.EMPTY_ARGUMENTS);
        }

        @Override
        public Object[] getArguments()
        {
            return arguments;
        }

        @Override
        public Method getMethod()
        {
            return method;
        }

        @Override
        public Object getProxy()
        {
            return proxy;
        }

        @Override
        public Object proceed() throws Throwable
        {
            try
            {
                return method.invoke(target, arguments);
            }
            catch (InvocationTargetException e)
            {
                throw e.getTargetException();
            }
        }
    }
}