jdk 动态代理

package com.bjsxt.aop;

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

public class LogInterceptor implements InvocationHandler {

private Object target;

public Object getTarget() {
return target;
}

public void setTarget(Object target) {
this.target = target;
}

public void beforeMethod(Method m) {

System.out.println(m.getName() + " start");
}

public Object invoke(Object proxy, Method m, Object[] args)
throws Throwable {
beforeMethod(m);
m.invoke(target, args);
return null;
}

}

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package com.bjsxt.dao;
import com.bjsxt.model.User;


public interface UserDAO {
public void save(User user);
public void delete();
}

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package com.bjsxt.dao.impl;

import com.bjsxt.dao.UserDAO;
import com.bjsxt.model.User;


public class UserDAOImpl implements UserDAO {

public void save(User user) {

//Hibernate
//JDBC
//XML
//NetWork
System.out.println("user saved!");
}

public void delete() {
System.out.println("user deteleted");

}

}

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package com.bjsxt.model;

public class User {
private String username;
private String password;
public String getUsername() {
return username;
}
public void setUsername(String username) {
this.username = username;
}
public String getPassword() {
return password;
}
public void setPassword(String password) {
this.password = password;
}
}


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package test.com.bjsxt.service;

import java.lang.reflect.Proxy;

import org.junit.Test;

import com.bjsxt.aop.LogInterceptor;
import com.bjsxt.dao.UserDAO;
import com.bjsxt.dao.impl.UserDAOImpl;
import com.bjsxt.model.User;

import junit.framework.TestCase;

public class UserServiceTest extends TestCase {

@Test
public void testProxy() {
UserDAO userDAO = new UserDAOImpl();
LogInterceptor li = new LogInterceptor();
li.setTarget(userDAO);
UserDAO userDAOProxy = (UserDAO)Proxy.newProxyInstance(userDAO.getClass().getClassLoader(), userDAO.getClass().getInterfaces(), li);
System.out.println(userDAOProxy.getClass());
userDAOProxy.delete();
userDAOProxy.save(new User());

}

}

userDAO是被代理对象  LogInterceptor就是一个切面类 在执行save方法之前我要给它织入一点业务逻辑代码 在这里就假设是beforeMethod,beforeMethod就是前置方法

程序运行的结果是:
delete start
user deteleted
save start
user saved