spring框架 aop:aspectj-autoproxy proxy-target-class=“true“用法理解

在spring框架中，集成使用AOP面向切面编程：
1、当一个类有接口的时候，那么spring默认使用的是JDK动态代理
2、如果当前类没有接口的时候，那么spring会默认使用CGLIB动态代理
3、如果一个类有接口的时候，还想要使用CGLIB动态代理，
那么就需要在spring的配置文件中加上 ：
aop:aspectj-autoproxy proxy-target-class="true" 属性。

切面类：MyAspect 

package com.ba01;
import org.aspectj.lang.ProceedingJoinPoint;
import org.aspectj.lang.annotation.*;
import java.util.Date;
@Aspect
public class MyAspect {
    @Around(value = "mypt()")
    public Object myAround(ProceedingJoinPoint joinPoint) throws Throwable {
        Object object = null;
        System.out.println("环绕通知，在目标方法之前调用，输出时间，" + new Date());
        //1、可以控制目标方法的执行
        String name = "";
        Object[] args = joinPoint.getArgs();
        if(args != null && args.length > 1){
            name = (String) args[0];
        }
        if(!"zhangshan".equals(name)){
            //2、目标方法的调用
            object = joinPoint.proceed();//相当于method.invoke();
        }
        System.out.println("环绕通知，在目标方法之后调用，输出时间，" + new Date());
        //3、可以直接修改方法的返回值
        object = "1234werqwe";
        return object;
    }
    @AfterThrowing(value = "execution(* *(..))",throwing = "ex")
    public void myafterThrowing(Exception ex){
        System.out.println("异常通知：" + ex.getMessage());
        //可以发送邮件，短信，来通知开发人员
    }
    @Before(value = "mypt())")
    public void myafterThrowing(){
        System.out.println("前置通知：");
    }
    @Pointcut(value = "execution(* *(..))")
    private void mypt(){
    }
}

接口SomeService 

public interface SomeService {
    public void doSome(String name,Integer age);
    public String doOther(String name,Integer age);
}

package com.ba01;
import com.ba01.SomeService;
import org.springframework.stereotype.Component;
public class SomeServiceImpl implements SomeService{
    @Override
    public String doOther(String name, Integer age) {
        System.out.println("====doOther方法===========");
        return "abcd";
    }
    @Override
    public void doSome(String name, Integer age) {
        System.out.println("====dosome方法===========");
    }
}

spring的xml配置

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xmlns:context="http://www.springframework.org/schema/context"
       xmlns:aop="http://www.springframework.org/schema/aop"
       xsi:schemaLocation="http://www.springframework.org/schema/beans
       http://www.springframework.org/schema/beans/spring-beans.xsd
       http://www.springframework.org/schema/context
       https://www.springframework.org/schema/context/spring-context.xsd http://www.springframework.org/schema/aop https://www.springframework.org/schema/aop/spring-aop.xsd">
    <!--声明目标对象-->
    <bean id="someService" class="com.ba01.SomeServiceImpl"/>
    <!--声明切面类对象-->
    <bean id="myAspect" class="com.ba01.MyAspect"/>
    <!--声明自动代理生成器
        aspectj-autoproxy:会把spring 容器中所有的目标对象，一次性的生成代理对象
    -->
    <aop:aspectj-autoproxy/>
</beans>

执行测试类，主要就是把获得的bean对象打印出来

@Test
    public void shouldAnswerWithTrue()
    {
        ApplicationContext context = new ClassPathXmlApplicationContext("beans.xml");
        SomeService someService =  (SomeService) context.getBean("someService");
        System.out.println(someService.getClass());
    }

class com.sun.proxy.$Proxy14
Process finished with exit code 0

public class SomeServiceImpl{
    public String doOther(String name, Integer age) {
        System.out.println("====doOther方法===========");
        return "abcd";
    }
    public void doSome(String name, Integer age) {
        System.out.println("====dosome方法===========");
    }
}

切面类不变，spring的xml文件也不变

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xmlns:context="http://www.springframework.org/schema/context"
       xmlns:aop="http://www.springframework.org/schema/aop"
       xsi:schemaLocation="http://www.springframework.org/schema/beans
       http://www.springframework.org/schema/beans/spring-beans.xsd
       http://www.springframework.org/schema/context
       https://www.springframework.org/schema/context/spring-context.xsd http://www.springframework.org/schema/aop https://www.springframework.org/schema/aop/spring-aop.xsd">
    <!--声明目标对象-->
    <bean id="someService" class="com.ba01.SomeServiceImpl"/>
    <!--声明切面类对象-->
    <bean id="myAspect" class="com.ba01.MyAspect"/>
    <!--声明自动代理生成器
        aspectj-autoproxy:会把spring 容器中所有的目标对象，一次性的生成代理对象
    -->
    <aop:aspectj-autoproxy/>
</beans>

直接运行测试类，注意此时是用的SomeServiceImpl ，而不是接口SomeService

@Test
    public void shouldAnswerWithTrue()
    {
        ApplicationContext context = new ClassPathXmlApplicationContext("beans.xml");
        SomeServiceImpl someService =  (SomeServiceImpl) context.getBean("someService");
        System.out.println(someService.getClass());
    }

运行结果，我们发现现在变成了CGLIB动态代理，这个是spring框架自动帮我们实现的

class com.ba01.SomeServiceImpl$$EnhancerBySpringCGLIB$$4ec165aa
Process finished with exit code 0

修改spring的xml文件

<beans>
...
<aop:aspectj-autoproxy proxy-target-class="true"/>
</beans>

public class SomeServiceImpl implements SomeService{
    @Override
    public String doOther(String name, Integer age) {
        System.out.println("====doOther方法===========");
        return "abcd";
    }
    @Override
    public void doSome(String name, Integer age) {
        System.out.println("====dosome方法===========");
    }
}

测试类泡一下

@Test
    public void shouldAnswerWithTrue()
    {
        ApplicationContext context = new ClassPathXmlApplicationContext("beans.xml");
        SomeService someService =  (SomeService) context.getBean("someService");
        System.out.println(someService.getClass());
    }

class com.ba01.SomeServiceImpl$$EnhancerBySpringCGLIB$$63108b69
Process finished with exit code 0