@EnableAspectAutoJAutoProxy_ Exposeproxy property

One 、@EnableAspectAutoJAutoProxy Turn on AOP function

@Target({
    ElementType.TYPE})
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Import({
    AspectJAutoProxyRegistrar.class})
public @interface EnableAspectJAutoProxy {
    
    boolean proxyTargetClass() default false;
    boolean exposeProxy() default false;
}

1. Attribute interpretation

• proxyTargetClass： Represents the implementation of dynamic proxy , If the value is set true, Indicates that proxy classes are based on CGLIB To achieve ; By default, the value is set to false Indicates that if the original class defines an interface, it passes JDK.Proxy Implementation is otherwise based on CGLIB To achieve .
• exposeProxy: exposeProxy=true Spring The current proxy object will be stored in ThreadLocal in

Two 、 About exposeProxy

1. Let's look at an example

• Interface ：

public interface IUserService {
    
   boolean showName();
   void showAge();
}

• Implementation interface

@Service
public class UserService implements IUserService {
    
    @Override
    public boolean showName() {
    
        System.out.println("UserService.showName");
        showAge();
        return false;
    }
    @Override
    public void showAge() {
    
        System.out.println("UserService.showAge");
    }
}

• section

@Component
@Aspect
public class MyAspect {
    
    @Before("execution(* com.aop.UserService.*(..))")
    @AfterReturning
    public void myBefore(JoinPoint joinPoint) {
    
        System.out.println("before invoke "+joinPoint.getSignature().getName());
}

• Config

@Configuration
@ComponentScan("com.aop")
@EnableAspectJAutoProxy
public class AppConfig {
    
}

• Test

public class TestAOP {
    
    public static void main(String[] args) {
    
        AnnotationConfigApplicationContext ctx = new AnnotationConfigApplicationContext(AppConfig.class);
        IUserService userService = (IUserService) ctx.getBean("userService");
        userService.showName();
    }
}

• result

before invoke showName
UserService.showName
UserService.showAge

• reflection ： Why not output before invoke showAge
• The reason is that ：

 public boolean showName() {
    
        System.out.println("UserService.showName");
        // The essence is this.showAge(), Here it is. UserService The original object of , Not by spring Strengthened Proxy Object to call 
        showAge();
        return false;
    }

2. resolvent ： The core is Get Spring Enhanced proxy object , Call again .

• Give Way UserService Perceive ApplicationContextAware, Make it from beanFactory Get Proxy Object capability . Be careful Out of commission new AnnotationConfigApplicationContext(), such Spring There will be two containers

@Service
public class UserService implements IUserService , ApplicationContextAware {
    
    private ApplicationContext applicationContext;
   @Override
    public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {
    
            this.applicationContext = applicationContext;
    }
    public boolean showName(){
    
        System.out.println("UserService.showName");
        IUserService userService = (IUserService) applicationContext.getBean("userService");
        userService.showAge();
        return true;
    }
    @Override
    public void showAge() {
    
        System.out.println("UserService.showAge");
    }
}
-----------------------------------------------------
 result ：
before invoke showName
UserService.showName
before invoke showAge
UserService.showAge

• stay ThreadLocal Get to the Proxy object , This is a Spring Capabilities provided , However, to enable this function, you need to set exposeProxy=true ： Store the current proxy object in ThreadLocal in

@Service
public class UserService implements IUserService {
    
   @Override
    public boolean showName() {
    
        System.out.println("UserService.showName");
        //TheadLocal in   Get proxy object   And call 
        IUserService userService = (IUserService) AopContext.currentProxy();
        userService.showAge();
        return true;
    }
    @Override
    public void showAge() {
    
        System.out.println("UserService.showAge");
    }
}

If not ：@EnableAspectJAutoProxy(exposeProxy = true), Report the following error ：

• Source code ：

stay Spring.JdkDynamicAopProxy.invoke() In the method , You can see the following ：

 if (this.advised.exposeProxy) {
    
                    oldProxy = AopContext.setCurrentProxy(proxy);
                    setProxyContext = true;
                }

3、 ... and 、Spring They don't advocate the above methods ,Spring The official document suggests , Don't call each other in proxy methods