Java jdk proxy、cglib、aspectj 三种常用代理示范

必须实现接口，没有实现接口用cglib.

package com.example.test.jdk_proxy;


public interface Animal {
    
    String say();
}

package com.example.test.jdk_proxy;


public class Cat implements Animal {
    
    @Override
    public String say() {
        return "喵喵喵~";
    }
}

package com.example.test.jdk_proxy;

import java.lang.reflect.Proxy;


public class ProxyDemo {
    public static void main(String[] args) {
        Cat cat = new Cat();
        Animal animalProxyInstance = (Animal) Proxy.newProxyInstance(Cat.class.getClassLoader(), Cat.class.getInterfaces(), (proxy, method, args1) -> {
            System.out.println("invoke before");
            Object result = method.invoke(cat, args1);
            System.out.println("invoke result: " + result);
            System.out.println("invoke after");
            return result;
        });
        animalProxyInstance.say();
    }
}

运行结果：

spring对于实现了接口的类会采用jdk proxy，否则使用cglib做动态代理。
也可以配置都使用cglib

package com.example.test.cglib;


public class Cat {
    
    public String write() {
        return "cat write letter";
    }
}

package com.example.test.cglib;

import org.springframework.cglib.proxy.Enhancer;
import org.springframework.cglib.proxy.MethodInterceptor;


public class CgLibDemo {
    public static void main(String[] args) {
        Enhancer enhancer = new Enhancer();
        enhancer.setSuperclass(Cat.class);
        enhancer.setCallback((MethodInterceptor) (object, method, args1, methodProxy) -> {
            System.out.println("invoke before");
            Object result = methodProxy.invokeSuper(object, args1);
            System.out.println("invoke result: " + result);
            System.out.println("invoke after");
            return result;
        });
        Cat cat = (Cat) enhancer.create();
        cat.write();
    }
}

运行结果：

package com.example.test.aspectj;

import org.springframework.stereotype.Component;


@Component
public class Dog {
    public String say() {
        return "汪汪汪";
    }
}

package com.example.test.aspectj.aspect;

import org.aspectj.lang.JoinPoint;
import org.aspectj.lang.ProceedingJoinPoint;
import org.aspectj.lang.annotation.*;
import org.springframework.stereotype.Component;


@Aspect
@Component
public class DogAspect {

    
    @Pointcut("execution(String com.example.test.aspectj.Dog.say())")
    public void dogSay() {

    }

    
    @Before(value = "dogSay()")
    public void before() {
        System.out.println("@Before executed");
    }

    
    @After(value = "dogSay()")
    public void after() {
        System.out.println("@After executed");
    }

    
    @Around(value = "dogSay()")
    public Object around(ProceedingJoinPoint joinPoint) {
        System.out.println("@Around before executed");
        Object result = null;
        try {
            result = joinPoint.proceed();
            System.out.println("@Around proceed result: " + result);
        } catch (Throwable e) {
            e.printStackTrace();
        }
        System.out.println("@Around after executed");
        return result;
    }

    
    @AfterReturning(value = "dogSay()", returning = "returnObject")
    public void afterReturning(JoinPoint joinPoint, Object returnObject) {
        System.out.println("@AfterReturning,result: " + returnObject);
    }

    
    @AfterThrowing(value = "dogSay()", throwing = "e")
    public void afterThrowing(Throwable e) {
        System.err.println("@AfterThrowing,error message: " + e.getMessage());
    }
}

package com.example.test.aspectj;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.boot.context.event.ApplicationReadyEvent;
import org.springframework.context.ApplicationListener;


@SpringBootApplication
public class Application implements ApplicationListener {
    @Autowired
    private Dog dog;

    public static void main(String[] args) {
        SpringApplication.run(Application.class, args);
    }

    
    @Override
    public void onApplicationEvent(ApplicationReadyEvent applicationReadyEvent) {
        System.out.println("call result: " + dog.say());
    }
}

运行结果：