动态代理

 示例代码

package DP;

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

/**
 * 通过动态代理的模式去拓展方法
 * 
 * @author renguanyu
 *
 */
public class DynamicProxyDemo {

    public static void main(String[] args) {

        /*
        System.getProperties().put("sun.misc.ProxyGenerator.saveGeneratedFiles", "true");
        System.getProperties().put("jdk.proxy.ProxyGenerator.saveGeneratedFiles", "true");
        */

        // 示例数据
        Emp e = new Emp("1", "liubei");
        // 业务对象
        Dao dao = new DaoImpl();

        // 通过动态代理，拓展方法
        InvocationHandler h = null;

        h = new DaoInvocationHandler1(dao);
        dao = (Dao) Proxy.newProxyInstance(ClassLoader.getSystemClassLoader(), new Class[] { Dao.class }, h);

        h = new DaoInvocationHandler2(dao);
        dao = (Dao) Proxy.newProxyInstance(ClassLoader.getSystemClassLoader(), new Class[] { Dao.class }, h);

        // 业务操作
        dao.save(e);
    }

}

interface Dao {

    void save(Emp e);

}

class DaoImpl implements Dao {

    @Override
    public void save(Emp e) {

        System.out.println("save -> " + e);

    }

}

class DaoInvocationHandler1 implements InvocationHandler {

    Dao dao;

    public DaoInvocationHandler1(Dao dao) {
        this.dao = dao;
    }

    @Override
    public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
        System.out.println("DaoInvocationHandler1 - start ");
        method.invoke(dao, args);
        System.out.println("DaoInvocationHandler1 - end ");
        return null;
    }

}

class DaoInvocationHandler2 implements InvocationHandler {

    Dao dao;

    public DaoInvocationHandler2(Dao dao) {
        this.dao = dao;
    }

    @Override
    public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
        System.out.println("DaoInvocationHandler2 - start ");
        method.invoke(dao, args);
        System.out.println("DaoInvocationHandler2 - end ");
        return null;
    }

}

class Emp {

    String id;
    String name;

    public Emp(String id, String name) {
        super();
        this.id = id;
        this.name = name;
    }

    @Override
    public String toString() {
        return "Emp [id=" + id + ", name=" + name + "]";
    }

}