This article takes you to understand the implementation of surround notification @around and final notification @after

Catalog

Surrounding the notification @Around

Execute the process ​ edit

Code implementation  

Interface

  Implementation class

Section class

​ edit   Surrounding the notification

Final notice @After

Add various notifications to a method

Alias the pointcut expression

---

Surrounding the notification @Around

  It is by intercepting the target method , Notification of enhancements before and after the target method . It is the most powerful notification , General business uses this notice . It can easily change the return value of the target method .

Execute the process

Code implementation  

Interface

  Implementation class

Section class

  Surrounding the notification

  @Aspect
@Component
public class MyAspect {
    /**
     *  Specification of surrounding notification method 
     * 1) Access rights are public
     * 2) The facet method has a return value , This return value is the return value of the target method 
     * 3) Method name customization 
     * 4) Method has parameters , This parameter is the target method 
     * 5) Avoid exceptions Throwable
     * 6) Use @Around Annotation declarations are around notifications 
     *    Parameters :
     *      value: Specify pointcut expression 
     */

    @Around(value = "execution(* com.bjpowernode.s03.*.*(..))")
    public Object myAround(ProceedingJoinPoint pjp) throws Throwable {
        // The forward cutting function is realized 
        System.out.println(" Pre function implementation in surround notification ............");
        // Target method call 
        Object obj = pjp.proceed(pjp.getArgs());
        // The back cutting function is realized 
        System.out.println(" Post function implementation in surround notification ............");
        return obj.toString().toUpperCase();  // Changed the return value of the target method 
    }
}

Final notice @After

  Whether or not the target method performs normally , The final notification code will be executed .

    

Add various notifications to a method

    

 

 

Alias the pointcut expression

Alias the pointcut expression @Pointcut
  If multiple facets cut into the same entry point , Aliases can be used to simplify development .
  Use @Pointcut annotation , Create an empty method , The name of this method is alias .

 

 

@Aspect
    @Component
    public class MyAspect {
        /**
         *  Specification of the final notification method 
         * 1) Access rights are public
         * 2) Method does not return a value 
         * 3) Method name customization 
         * 4) Method has no parameters , If so, it can only be JoinPoint
         * 5) Use @After The note indicates that it is the final notice 
         *    Parameters :
         *     value: Specify pointcut expression 
         */
        @After(value = "mycut()")
        public void myAfter(){
            System.out.println(" The function of final notification ........");
        }

        @Before(value = "mycut()")
        public void myBefore(){
            System.out.println(" The function of pre notification ........");
        }

        @AfterReturning(value = "mycut()",returning = "obj")
        public void myAfterReturning(Object obj){
            System.out.println(" Post notification function ........");
        }
        @Around(value = "mycut()")
        public Object myAround(ProceedingJoinPoint pjp) throws Throwable {
            System.out.println(" Surround the function of pre notification in notification ........");
            Object obj = pjp.proceed(pjp.getArgs());
            System.out.println(" Surround the function of post notification in notification ........");
            return obj;
        }

        @Pointcut(value = "execution(* com.bjpowernode.s04.*.*(..))")
        public void mycut(){}
    }

test

 

    (1)Before: Enhance before the target method is called ,@Before Just specify the pointcut expression

 (2)AfterReturning: Enhance after the target method is completed normally ,@AfterReturning Except after specifying the pointcut expression , You can also specify a return value parameter name returning, Represents the return value of the target method

 (3)AfterThrowing: Mainly used to handle unhandled exceptions in the program ,@AfterThrowing Except after specifying the pointcut expression , You can also specify a throwing The return value parameter name of , You can use this parameter name to access the exception object thrown in the target method

 (4)After: Enhance after the target method is completed , No matter when the target method is successfully completed [email protected] You can specify a pointcut expression

 (5)Around: Surrounding the notification , Enhance before and after the completion of the target method , Surround notification is the most important type of notification , Like business , Logs and so on are all around notifications , Note that the core of programming is a ProceedingJoinPoint