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AOP Overview
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AOP stands for Aspect-Oriented Programming. It is a powerful programming paradigm that helps modularize cross-cutting concerns - functionalities that cut across multiple parts of an application, like:

  • Logging
  • Security
  • Transaction management
  • Performance monitoring
Instead of adding these concerns directly inside your business logic, AOP keeps them separate - making your code cleaner, easier to maintain, and less error-prone.



Why do we need AOP ?

Imagine you have a Payment Service. Before a user can make a payment, they need to be logged in. Instead of adding login check code in every payment method, you can use AOP to handle this cross-cutting concern automatically.

This way, you

  • Avoid duplicate code
  • Keep business logic clean
  • Centralize your cross-cutting logic



Key Point

  • OOP (Object-Oriented Programming) is about classes and objects
  • AOP (Aspect-Oriented Programming) is about aspects



Basic Terminologies in AOP


TermMeaning
AspectA module / class that encapsulates a cross-cutting concern (e.g., logging). Contains advices and pointcuts.
AdviceThe action or code to run at a specific join point. Types include

  • Before Advice: Runs before method execution
  • After Advice: Runs after method execution, no matter what
  • After Returning Advice: Runs only if method completes successfully
  • After Throwing Advice: Runs only if method throws an exception
  • Around Advice: Wraps method; can control execution and return value
Join PointA point in the execution of your program (e.g., method call) where advice can be applied
PointcutDefines which join points the advice should run on (e.g., all methods in a package)
WeavingThe process of linking aspects with other application code to create the final executable system



How AOP works in Spring

  • You define an aspect (e.g., a class with @Aspect annotation)
  • You write advices (methods annotated with @Before, @After, etc.)
  • You configure pointcuts to decide where the advices apply
  • Spring automatically weaves your advice into the business methods at runtime



Example Use Cases

  • Logging method calls
  • Checking permissions before executing methods
  • Managing transactions
  • Performance monitoring (e.g., measuring execution time)



Conclusion

AOP makes it easier to separate cross-cutting concerns from business logic leading to cleaner, maintainable, and modular applications.


If you had like, I can also

  • Create a complete Spring Boot AOP example with code
  • Explain annotations like @Aspect, @Before, @After
  • Show step-by-step how to configure AOP in Spring Boot