AOP那些事（一）

aop 的实现方式有四种。

1 jdk的动态代理。

2 CGLib代理。

3 AspectJ

4 instrumentation

下面介绍一下proxy

package proxy;

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

/**
 * Created by dingshuangkun on 2018/1/8.
 */
public class DynamicProxy implements InvocationHandler {

    private Object target;

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

    public <T> T getProxy() {
        return (T) Proxy.newProxyInstance(
                target.getClass().getClassLoader(),
                target.getClass().getInterfaces(),
                this);
    }

    @Override
    public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
        before();
        Object obj = method.invoke(target, args);
        after();
        return obj;
    }

    public void before() {
        System.out.println("------before------");
    }

    public void after() {
        System.out.println("-------after---------");
    }
}

实现jdk的动态代理很是简单，实现InvocationHandler接口便可。

下面作个测试

package aop;

/**
 * Created by dingshuangkun on 2018/1/8.
 */
public interface Greeting {
    void sayHello(String name);
    void sayNiHao(String name);
}

Greeting 实现类

package aop.impl;

import aop.Greeting;

/**
 * Created by dingshuangkun on 2018/1/8.
 */
public class GreetingImpl implements Greeting {
    @Override
    public void sayHello(String name) {
        System.out.println("hello "+name);
    }
    @Override
    public void sayNiHao(String name) {
        System.out.println("niHao "+name);
    }
}

单测

import aop.Greeting;
import aop.impl.GreetingImpl;
import org.junit.Test;
import proxy.DynamicProxy;

/**
 * Created by dingshuangkun on 2018/1/8.
 */
public class AopTest {

    @Test
    public void proxyTest(){
        Greeting greeting = new GreetingImpl();
        DynamicProxy dynamicProxy = new DynamicProxy(greeting);
        Greeting  greetingProxy = dynamicProxy.getProxy();
        greetingProxy.sayHello("ding");
        greetingProxy.sayNiHao("ding");
    }
}

运行结果

------before------ hello ding -------after--------- ------before------ niHao ding -------after---------