spring aop

JDK动态代理和CGLib代理

• JDK的代理
  代理类

package com.xiaoyuxixi.yxrzbj;

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


/**
 * Created by yuxi on 2018/1/6.
 */
public class JdkProxy implements InvocationHandler {
    private Object target;//代理对象

    public JdkProxy(Object object) {
        this.target = object;
    }

    /**
     * 获取代理对象
     *
     * @param <T>
     * @return
     */
    public <T> T getProxy() {
        return (T) Proxy.newProxyInstance(
                target.getClass().getClassLoader(),
                target.getClass().getInterfaces(),
                this
        );

    }

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

    private void before() {
        System.out.println("hello before");
    }

    private void after() {
        System.out.println("hello after");
    }
}

被代理接口

package com.xiaoyuxixi.yxrzbj;

/**
 * Created by yuxi on 2018/1/6.
 */
public interface Hello {
    public  void  sayHello() ;
}

被代理实现类

package com.xiaoyuxixi.yxrzbj;

/**
 * Created by yuxi on 2018/1/6.
 */
public class HelloImpl implements Hello{
    public void sayHello() {
        System.out.println("hello jdk 动态代理");
    }
}

启动类：

package com.xiaoyuxixi.yxrzbj;

/**
 * Created by yuxi on 2018/1/6.
 */
public class Main {
    public static void main(String[] args) {
//        Hello hello = new HelloImpl();
//        hello.sayHello();

        //动态代理
        Hello hello = new JdkProxy(new HelloImpl()).getProxy();
        hello.sayHello();
    }
}

jdk的动态代理是针对接口的，如果不是接口实现类的方式是无效的，这也是JDK代理的局限性，因此有了cglib代理。

• CGLib代理
  cglib代理类：

package com.xiaoyuxixi.yxrzbj.cglib;

import org.mockito.cglib.proxy.Enhancer;
import org.mockito.cglib.proxy.MethodInterceptor;
import org.mockito.cglib.proxy.MethodProxy;

import java.lang.reflect.Method;


/**
 * Created by yuxi on 2018/1/6.
 */
public class CglibProxy implements MethodInterceptor {

    private static CglibProxy cglibProxy = new CglibProxy();

    private CglibProxy() {

    }
    public static CglibProxy getInstance() {
        return cglibProxy;
    }

    /**
     * 获取代理对象
     *
     * @param cls
     * @param <T>
     * @return
     */
    public <T> T getProxy(Class<T> cls) {
        return (T) Enhancer.create(cls, this);
    }

    public Object intercept(Object target, Method method, Object[] args, MethodProxy proxy) throws Throwable {
        before();
        Object result = proxy.invokeSuper(target, args);
        after();
        return result;
    }

    private void before() {
        System.out.println("hello cglib before");
    }

    private void after() {
        System.out.println("hello cglib after");
    }
}

启动类：

package com.xiaoyuxixi.yxrzbj.cglib;

import com.xiaoyuxixi.yxrzbj.jdkproxy.Hello;
import com.xiaoyuxixi.yxrzbj.jdkproxy.HelloImpl;

/**
 * Created by yuxi on 2018/1/6.
 */
public class Main {
    public static void main(String[] args) {
        Hello hello = CglibProxy.getInstance(). getProxy(HelloImpl.class);
        hello.sayHello();
    }
}

aop 相关术语

• 通知 advice
• 连接点 joinpoint
• 切点 pointcut
• 切面
• 引入introduction

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spring aop 是什么？

spring aop 有什么好处？

spring aop 是如何实现的？

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