Practice Topics

Configuration

1. Add dependencies:
   • Spring framework [URL]
   • AspectJ Weaver: supports AOP (avoid Beta version) [URL]
2. Create Spring AOP Java configuaration class with @Configuration, @EnableAspectJAutoProxy, @ComponentScan [JavaConfig].
3. Create bean class with @Component [Account].
4. Create Main app class [LoggingApp]
   1. Read Spring config Java class to get the context

   AnnotationConfigApplicationContext context = new AnnotationConfigApplicationContext(JavaConfig.class);
   

   2. Get bean class from Spring container

   BeanClass aBean = context.getBean("aBean", BeanClass.class);
   

   3. Call business methods of the bean
   4. Close the context: context.close();
5. Create Aspect class with @Aspect and @Component (to group related Advices) [LoggingAspect]
   1. Setup logger [java.util.logging.Logger] or use @Logger from Lombok (to log Advices output in the same thread? as Spring)
   2. Setup Pointcut declarations with @Pointcut (to associate business methods of bean with Advices)
   3. Create Advices (to execute whatever code with associated business methods)

Concepts

• @EnableAspectJAutoProxy
• AnnotationConfigApplicationContext
• Aspect with @Aspect
• Advice [LoggingAspect]
  • @Before: run before the method
  • @AfterReturning: run after the method (success execution), use returning to get returning result
  • @AfterThrowing: run after the method (if exception thrown), use throwing and Throwable the capture the exception, can not handle exception
  • @After: run after the method (regardless of outcome)
  • @Around: run before and after the method, use ProceedingJoinPoint.proceed() to execute target method when desired, can handle/rethrow exception using try catch block
• Pointcut expression: execution(return_type package.class.method(params))
  • Wildcards [LoggingAspect]
    • (): no args
    • (*): one arg, any types
    • (..): zero or more args, any types
    • (fully qualified classname)
  • Declare with @Pointcut [CommonAspect]
  • Combine pointcut expressions using &&, ||, ! [CommonAspect]
• @Order: Decide the execution order of all Advices in a Aspect
  • Lower numbers have higher predence
  • Negative numbers are allowed
  • Does not have to be consecutive
• JoinPoint: contains metadata of the business method [TestingAspect]
  • Get method signature by MethodSignature and JoinPoint.getSignature()
  • Get method parameters by Objec[] and JoinPoint.getArgs()

Notes - Tips

• 📌 Quick copy fully qualified classname from that class
• 📌 Group related advices into one Aspect to order with @Order (i.e., logging aspect, testing aspect)
• 📌 Declare public pointcut expressions in a common Aspect to share with other Aspects [CommonAspect].
• ℹ️ Order execution: @Before -> @Around (before) -> Business method -> @Around (after) -> @After -> @AfterThrowing