Dynamic proxy interface and subclasses

Dynamic Agent:

    Features: use with the bytecode to create, with the use loading
    effect: not modify the source code on the basis of the method of enhancing
    Classification:
        Based on Dynamic agent interface
        dynamic proxy subclasses based

First, based on dynamic agent interface:

    Class involved: Proxy
    Provider: the JDK
    how to create a proxy object:
        using newProxyInstance methods of the Proxy class
    creation requires proxy objects:
        the proxy class happened implements an interface, if not can not be used
    newProxyInstance method parameters:
        ClassLoader: class loader
            proxy object for loading bytecode, and the same proxy object class loader
        class []: bytecode array
            to allow the object and a proxy agent objects with the same method
        InvocationHandler: code for providing enhanced
            let how to write agents are generally the class that implements the interface, are usually anonymous inner classes, but not necessary

public interface IProducer {
    public void saleProduct(Float money);
    public void afterService(Float money);
}

public class Producer implements IProducer{
    /**
     * 销售
     * @param money
     */
    public void saleProduct(Float money){
        System.out.println("销售产品，并拿到钱："+money);
    }
    /**
     * 售后
     * @param money
     */
    public void afterService(Float money){
        System.out.println("提供售后服务，并拿到钱："+money);
    }
}

import com.ycl.proxy.IProducer;
import com.ycl.proxy.Producer;
import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;
/**
* 模拟一个消费者
*/
public class Client {
    public static void main(String[] args) {
        final Producer producer = new Producer();
        IProducer proxyProducer = (IProducer) Proxy.newProxyInstance(producer.getClass().getClassLoader(),
                producer.getClass().getInterfaces(), new InvocationHandler() {
                    /**
                     * 作用：执行被代理对象的任何接口方法都会经过该方法
                     * @param proxy     代理对象的引用
                     * @param method    当前执行的方法
                     * @param args      当前执行方法所需的参数
                     * @return          和被代理对象有相同的返回值
                     * @throws Throwable
                     */
                    public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
                        //增强的代码
                        Object value = null;
                        Float money = (Float) args[0];
                        if ("saleProduct".equals(method.getName())){
                            value = method.invoke(producer,money*0.8f);
                        }
                        return value;
                    }
                });
        proxyProducer.saleProduct(10000f);
    }
}

Second, based on dynamic proxy subclasses:

    Related categories: Enhancer
    Provider: third-party libraries cglib
    how to create a proxy object:
        create method Enhancer class
    to create a proxy object request:
        the proxy class can not be the final class
    parameter create method:
        Class: byte code
            specifies the proxy object bytecode
        Callback: code for providing enhanced

import net.sf.cglib.proxy.Enhancer;
import net.sf.cglib.proxy.MethodInterceptor;
import net.sf.cglib.proxy.MethodProxy;
import java.lang.reflect.Method;
/**
* 模拟一个消费者
*/
public class Client {
    public static void main(String[] args) {
        final Producer producer = new Producer();
        Producer cglibEnhancer = (Producer) Enhancer.create(producer.getClass(), new MethodInterceptor() {
            /**
             * 作用：执行被代理对象的任何接口方法都会经过该方法
             * @param o
             * @param method
             * @param objects
             *      以上三个参数和基于接口的动态代理中invoke方法的参数是一样的
             * @param methodProxy：当前执行方法的代理对象
             * @return
             * @throws Throwable
             */
            public Object intercept(Object o, Method method, Object[] objects, MethodProxy methodProxy) throws Throwable {
                //增强的代码
                Object value = null;
                Float money = (Float) objects[0];
                if ("saleProduct".equals(method.getName())){
                    value = method.invoke(producer,money*0.8f);
                }
                return value;
            }
        });
        cglibEnhancer.saleProduct(10000f);
    }
}