Jdk dynamic proxy usage and cglib

A: JDK dynamic proxy

JDK dynamic proxy class agent used in the program to call when the agent class object is actually created by the JVM , the JVM passed in accordance with the business to achieve the object class and method names, dynamically create a proxy class and the class file byte code execution engine, and then call the method by which the agent class object.

Case

1, the definition of interfaces and service implementation class

package com.yjc.jdkproxy;

public interface DoSomeService {
    void doSome();
}
-------------------------------------------

package com.yjc.jdkproxy;

public class DoSomeServiceImpl implements DoSomeService {
    @Override
    public void doSome() {
        System.out.println("doSome++++++++++++++++++==");
    }
}

2. Call management interface to create a dynamic proxy class InvocationHandler

com.yjc.jdkproxy Package; 

Import java.lang.reflect.InvocationHandler; 
Import the java.lang.reflect.Method; 

public class DoSomeHandler the implements of InvocationHandler { 
  // service implementation class object which is actually used to call a business method 
    private Object target ; 
    @Override 
    public Invoke Object (Object Proxy, Method, Method, Object [] args) throws the Throwable { 
        System.out.println ( "before --------------------- ------- "); 
 　　　　 // call the real business methods 
        Object = Method.invoke the invoke (target, args); 
        System.out.println (" the After ------------- -------------- "); 
        return Invoke; 
    } 

    public DoSomeHandler (Object target) { 
        this.target = target; // implementation class object parameter receiving traffic 
    }

    public DoSomeHandler() {
    }
}

testing method

package com.yjc.jdkproxy;

import sun.misc.ProxyGenerator;

import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.lang.reflect.Proxy;

public class JdkProxyTest {
    public static void main(String[] args) throws IOException {
        DoSomeService doSomeService=new DoSomeServiceImpl();
 　　　　//通过反射机制，创建一个代理类对象实例并返回。用户进行方法调用时使用

        //创建代理对象时，需要传递该业务类的类加载器（用来获取业务实现类的元数据，在包装方法是调用真正的业务方法）、接口、handler实现类

        DoSomeService o = (DoSomeService)Proxy.newProxyInstance(doSomeService.getClass().getClassLoader(), new Class[]{DoSomeService.class}, new DoSomeHandler(doSomeService));
        //调用目标函数
　　　　  o.doSome();
　　　　　　//将内存中代理的类生成到本地
        byte[] $proxy0s = ProxyGenerator.generateProxyClass("$proxy0", new Class[]{DoSomeService.class});
        FileOutputStream fos=new FileOutputStream("F:/$proxy0.class");
        fos.write($proxy0s);
        fos.flush();
        fos.close();
    }
}

二:CGLIB动态代理

     cglib是针对类来实现代理的，原理是对指定的业务类生成一个子类，并覆盖其中业务方法实现代理。因为采用的是继承，所以不能对final修饰的类进行代理。

　cglib和jdk动态代理的区别就是,cglib无需业务接口也可以实现动态代理,而jdk是在业务接口的基础上进行实现的,没有接口不行。cglib也需要项目对cglib的支持,需要引入依赖

业务类

 

package com.yjc.cglibproxy;

public class DoSomeServiceImpl {

    public void doSome() {
        System.out.println("doSome++++++++++++++++++==");
    }
}

 

代理类

package com.yjc.cglibproxy;

import net.sf.cglib.proxy.MethodInterceptor;
import net.sf.cglib.proxy.MethodProxy;

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

public class DoSomeHandler implements MethodInterceptor {
    //目标对象
    private  Object target;


    public DoSomeHandler(Object target) {
        this.target = target;
    }

    public DoSomeHandler() {
    }

/**
* 
* 方法描述 当对基于代理的方法回调时，在调用原方法之前会调用该方法
* 拦截对目标方法的调用
*
* @param obj 代理对象
* @param method 拦截的方法
* @param args 拦截的方法的参数
* @param proxy 代理
* @return
* @throws Throwable
*/

    @Override
    public Object intercept(Object o, Method method, Object[] objects, MethodProxy methodProxy) throws Throwable {
        System.out.println("before==========================");
        Object invoke = method.invoke(target, objects);
        System.out.println("after============================");
        return invoke;
    }
}

测试类

package com.yjc.cglibproxy;

import net.sf.cglib.proxy.Enhancer;

public class CglibProxyTest {
    public static void main(String[] args) {
        Enhancer enhancer=new Enhancer(); 

// 设置目标对象的Class

enhancer.setSuperclass(DoSomeServiceImpl.class); 

  // 设置回调操作，相当于InvocationHandler

enhancer.setCallback(new DoSomeHandler(new DoSomeServiceImpl()));
 DoSomeServiceImpl o =(DoSomeServiceImpl) enhancer.create();
 o.doSome(); 
} }