AOP面向切面编程

责任链模式

Spring 创建 AOP 代理类时序图

代理模式。

AOP代理

package com.imooc.chain;
Chain与ChainHandler之间的函数回调设计，遍历Chain中的ChainHandler执行相关方法/**
 * Created by cat on 2017-02-28.
 */
public abstract class ChainHandler {

    public void execute(Chain chain){
        handleProcess();
        chain.proceed();
    }

    protected abstract void handleProcess();
}
package com.imooc.chain;

import java.util.List;

/**
 * Created by cat on 2017-02-28.
 */
public class Chain {

    private List<ChainHandler> handlers;

    private int index = 0;

    public Chain(List<ChainHandler> handlers) {
        this.handlers = handlers;
    }

    public void proceed(){
        if(index >= handlers.size()){
            return ;
        }
        handlers.get(index++).execute(this);
    }
}

/**
 * Created by cat on 2017-02-28.
 */
public class ChainClient {
    static class ChainHandlerA extends ChainHandler{
        @Override
        protected void handleProcess() {
            System.out.println("handle by chain a");
        }
    }
    static class ChainHandlerB extends ChainHandler{
        @Override
        protected void handleProcess() {
            System.out.println("handle by chain b");
        }
    }
    static class ChainHandlerC extends ChainHandler{
        @Override
        protected void handleProcess() {
            System.out.println("handle by chain c");
        }
    }

    public static void main(String[] args){
        List<ChainHandler> handlers = Arrays.asList(
                new ChainHandlerA(),
                new ChainHandlerB(),
                new ChainHandlerC()
        );
        Chain chain = new Chain(handlers);
        chain.proceed();
    }
}

责任链的调用

/**
 * Created by cat on 2017-02-28.
 */
public abstract class Handler {

    private Handler sucessor;

    public Handler getSucessor() {
        return sucessor;
    }

    public void setSucessor(Handler sucessor) {
        this.sucessor = sucessor;
    }

    public void execute(){
        handleProcess();
        if(sucessor != null){
            sucessor.execute();
        }
    }

    protected abstract void handleProcess();
}
package com.imooc.chain;

/**
 * Created by cat on 2017-02-28.
 */
public class Client {
    static class HandlerA extends Handler{
        @Override
        protected void handleProcess() {
            System.out.println("handle by a");
        }
    }
    static class HandlerB extends Handler{
        @Override
        protected void handleProcess() {
            System.out.println("handle by b");
        }
    }
    static class HandlerC extends Handler{
        @Override
        protected void handleProcess() {
            System.out.println("handle by c");
        }
    }

    public static void main(String[] args){
        Handler handlerA = new HandlerA();
        Handler handlerB = new HandlerB();
        Handler handlerC = new HandlerC();

        handlerA.setSucessor(handlerB);
        handlerB.setSucessor(handlerC);

        handlerA.execute();
    }
}

责任链模式

强制使用Cglib代理

springAOP的代理分情况使用jdk或者cglib的动态代理。

Spring如何选择使用jdk代理还是cglib代理？

1、如果目标对象实现了接口，默认使用JDK代理

2、如果目标对象没有实现接口，默认使用cglib代理

3、如果目标对象实现了接口，但我们可以强制使用cglib代理，方法如下：

@SpringBootApplication @EnableAspectJAutoProxy(proxyTargetClass = true)

Spring 如何代理

JDK与Cglib代理对比： 1：JDK只能针对有接口的类的接口方法进行动态代理； 2：Cglib基于继承来实现代理，无法对static、final类进行代理； 3：Cglib基于继承来实现代理，无法对private、static方法进行代理。

public class Client {<br/><br/>&nbsp;&nbsp;&nbsp; public static void main(String[] args){<br/>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; Enhancer enhancer = new Enhancer();<br/>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; enhancer.setSuperclass(RealSubject.class);<br/>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; enhancer.setCallback(new DemoMethodInterceptor());<br/>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; Subject subject = (Subject) enhancer.create();<br/>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; subject.hello();<br/>&nbsp;&nbsp;&nbsp; }<br/>}

public class DemoMethodInterceptor implements MethodInterceptor{
    @Override
    public Object intercept(Object obj, Method method, Object[] args, MethodProxy proxy) throws Throwable {
        System.out.println("before in cglib");
        Object result = null;
        try{
            result = proxy.invokeSuper(obj, args);
        }catch (Exception e){
            System.out.println("get ex:"+e.getMessage());
            throw e;
        }finally {
            System.out.println("after in cglib");
        }
        return result;
    }
}