手写aop

package com.demo;


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


// 测试接口和类
interface Waiter {
    //服务方法
    public void server();
}

class ManWaiter implements Waiter {

    @Override
    public void server() {
        System.out.println("服务中");
    }
}

// aop框架
interface BeforeAdvice {
    public void before();
}

interface AfterAdvice {
    public void after();
}


/**
 * @author sunwenfei
 * @date 2021-08-13 14:00
 */
public class ProxyFactory {

    private Object targetObject;//目标对象
    private BeforeAdvice beforeAdvice;//前值增强
    private AfterAdvice afterAdvice;//后置增强

    public Object getTargetObject() {
        return targetObject;
    }

    public void setTargetObject(Object targetObject) {
        this.targetObject = targetObject;
    }

    public BeforeAdvice getBeforeAdvice() {
        return beforeAdvice;
    }

    public void setBeforeAdvice(BeforeAdvice beforeAdvice) {
        this.beforeAdvice = beforeAdvice;
    }

    public AfterAdvice getAfterAdvice() {
        return afterAdvice;
    }

    public void setAfterAdvice(AfterAdvice afterAdvice) {
        this.afterAdvice = afterAdvice;
    }

    /**
     * 用来生成代理对象
     * @return
     */
    public Object creatProxy() {
        /**
         * 给出三个参数
         */
        ClassLoader classLoader = this.getClass().getClassLoader();
        //获取当前类型所实现的所有接口类型
        Class[] interfaces = targetObject.getClass().getInterfaces();

        InvocationHandler invocationHandler = new InvocationHandler() {
            @Override
            public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
                /**
                 * 在调用代理对象的方法时，会执行这里的内容
                 */
                if(beforeAdvice != null) {
                    beforeAdvice.before();
                }
                Object result = method.invoke(targetObject, args);//调用目标对象的目标方法
                //执行后续增强
                afterAdvice.after();

                //返回目标对象的返回值
                return result;
            }
        };
        /**
         * 2、得到代理对象
         */
        Object proxyObject = Proxy.newProxyInstance(classLoader, interfaces, invocationHandler);
        return proxyObject;

    }

    public static void main(String[] args) {

        ProxyFactory proxyFactory = new ProxyFactory();//创建工厂
        proxyFactory.setTargetObject(new ManWaiter());//设置目标对象
        //设置前置增强
        proxyFactory.setBeforeAdvice(new BeforeAdvice() {
            @Override
            public void before() {
                System.out.println("客户你好");
            }
        });
        //设置后置增强
        proxyFactory.setAfterAdvice(new AfterAdvice() {
            @Override
            public void after() {
                System.out.println("客户再见");
            }
        });
        Waiter waiter = (Waiter) proxyFactory.creatProxy();
        waiter.server();
    }
}

　　https://zhuanlan.zhihu.com/p/37732577