Spring aop
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This document discusses Spring AOP (Aspect Oriented Programming) and provides examples of how to implement cross-cutting concerns in a Spring application. It defines key AOP concepts like advice, aspect, pointcut, and joint point. It also describes the different types of AOP advices in Spring like before, after returning, after throwing and around advices. The document compares Spring AOP to AspectJ and provides code samples and use cases of implementing AOP.
Spring aop
- 2. Spring AOP Features • What are cross cutting concerns? • How do you implement cross cutting concerns in an application? • If you would want to log every request to a web application, what are the options you can think of? • If you would want to track performance of every request, what options can you think of? • What is an Advice, Aspect, Pointcut and Joint Point, Weaving ? • What are the different types of AOP Advices Types? • How do you implement AOP with Spring Boot? • What are the AOP Best Practices?
- 3. Use Case : Business Problems • Read/write locks. Instead of replicating the same snippet, I used an aspect to define the methods that needed a read lock or an exclusive lock. • Exception Handling: don't need to repeat the horrible list of try ... catch, catch, catch etc - also means the exception handling is guaranteed to be consistent. • Can use it to track events in the system, whenever some object is CRUD you can send an event to your event system. • Can use it for sending web/ios/email notifications before /after any method call. • Audit logging (the gold standard AOP use case). Its a bit coarse but the general approach is to annotate methods that represent some auditable action. Combined with something like Spring Security, we can get a pretty good idea of: o who the user is o what method they're invoking o what data they're providing o what time the method was invoked o whether the invocation was successful or not (i.e., if an exception was thrown)
- 4. What can be build in Spring • Airline reservation system • Inventory Management • Banking / Finance Systems • Social Network • Security Models • Mobile clients • Messaging Systems
- 5. Cross cutting concerns Applications are generally developed with multiple layers. A typical Java application has : Web Layer - Exposing the services to outside world using REST or a web application Business Layer - Business Logic Data Layer - Persistence Logic While the responsibilities of each of these layers are different, there are a few common aspects that apply to all layers Logging Security
- 6. Advice, Aspect, Pointcut, Joint Point, Weaving • Advice – Indicate the action to take either before or after the method execution. • Pointcut – Indicate which method should be intercept, by method name or regular expression pattern. • Advisor – Group ‘Advice’ and ‘Pointcut’ into a single unit, and pass it to a proxy factory object.
- 9. Spring AOP AspectJ Implemented in pure Java Implemented using extensions of Java programming language No need for separate compilation process Needs AspectJ compiler (ajc) unless LTW is set up Only runtime weaving is available Runtime weaving is not available. Supports compile-time, post-compile, and load-time Weaving Less Powerful – only supports method level weaving More Powerful – can weave fields, methods, constructors, static initializers, final class/methods, etc… Can only be implemented on beans managed by Spring container Can be implemented on all domain objects Supports only method execution pointcuts Support all pointcuts Proxies are created of targeted objects, and aspects are applied on these proxies Aspects are weaved directly into code before application is executed (before runtime) Much slower than AspectJ Better Performance Easy to learn and apply Comparatively more complicated than Spring AOP Difference between Spring AOP and AspectJ
- 10. Pointcut Expression Examples • The execution of any public method • execution(public * * (…)) • The Execution of any method begin with set • execution(* set*(…)) • The Execution of any method defined by Service Interface • execution(* com.dbschenker.spring.AopService.*(…)) • The Execution of any method defined in Dao Package • execution(* com.dbschenker.spring.dao.*.*(…))
- 11. AOP Advice Types • Before Advice: These advices runs before the execution of join point methods. We can use @Before annotation to mark an advice type as Before advice. • After (finally) Advice: An advice that gets executed after the join point method finishes executing, whether normally or by throwing an exception. We can create after advice using @After annotation. • After Returning Advice: Sometimes we want advice methods to execute only if the join point method executes normally. We can use @AfterReturning annotation to mark a method as after returning advice. • After Throwing Advice: This advice gets executed only when join point method throws exception, we can use it to rollback the transaction declaratively. We use @AfterThrowing annotation for this type of advice. • Around Advice: This is the most important and powerful advice. This advice surrounds the join point method and we can also choose whether to execute the join point method or not. We can write advice code that gets executed before and after the execution of the join point method. It is the responsibility of around advice to invoke the join point method and return values if the method is returning something. We use @Around annotation to create around advice methods.
- 12. Advice Hierarchy
- 13. codes / examples
- 14. REFERNCES • https://www.Springsource.org • https://Start.spring.io • https://docs.spring.io/spring/docs/3.2.x/spring-framework- reference/html/mvc.html • http://www.baeldung.com/spring-aop • Downloads: http://www.eclipse.org/aspectj/downloads.php