Spring aop

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Spring aop

  1. 1. Spring AOP ASPECT ORIENTED PROGRAMMING
  2. 2. Spring AOP - Introduction Aspect – Unit of Modularity  Entails breaking down program logic into distinct parts called socalled concerns. The functions that span multiple points of an application are called cross-cutting concerns  Cross-cutting concerns are conceptually separate from the application's business logic. 
  3. 3. AOP in Business  Logging  Transaction Management – Declarative  Caching  Security
  4. 4. AOP Terminologies  Aspect  Advice  Join Point  Pointcut  Introduction  Target Object  Weaving
  5. 5. AOP Advice   This is the actual action to be taken either before or after the method execution. This is actual piece of code that is invoked during program execution by Spring AOP framework.
  6. 6. Types of Advices      Before - Run advice before the a method execution. After - Run advice after the a method execution regardless of its outcome. After Returning - Run advice after the a method execution only if method completes successfully. After throwing - Run advice after the a method execution only if method exits by throwing an exception. Around- Run advice before and after the advised method is invoked.
  7. 7. Advices - Examples  @Before("execution(* *.*(..))")  @After("execution(* *.*(..))")  @AfterReturning("execution(* *.*(..))")  @AfterThrowing("execution(* *.*(..))")  @Around("execution(* *.*(..))")
  8. 8. Aspects Implementation  XML Schema Based  Annotaion Based
  9. 9. Join Point   An Advice is applied to different program execution points, which are called join points. An Advice to take the correct action, it often requires detailed information about join points.
  10. 10. Accessing Join Point Information  Kind  Method signature  Argument values  Target Object  Proxy Object
  11. 11. AspectJ Precedence  More than one Aspect classes – need Precedence  How to implement?  Ordered Interface  Order Annotation
  12. 12. Point Cut Expressions    It is a powerful expression language that can match various kinds of join points. Indicate which method should be intercept, by method name or regular expression pattern. expression(<method scope> <return type> <fully qualified class name>.*(parametes))
  13. 13. Continue..,   method scope: Advice will be applied to all the methods having this scope. For e.g., public, private, etc. Please note that Spring AOP only supports advising public methods. return type: Advice will be applied to all the methods having this return type.
  14. 14. Continue..,   fully qualified class name: Advice will be applied to all the methods of this type. If the class and advice are in the same package then package name is not required parameters: You can also filter the method names based on the types. Two dots(..) means any number and type of parameters.
  15. 15. Pointcut Examples    execution(* com.aspects.pointcut.DemoClass.*(..)) : This advice will be applied to all the methods of DemoClass. execution(* DemoClass.*(..)): You can omit the package if the DemoClass and the advice is in the same package. execution(public * DemoClass.*(..)): This advice will be applied to the public methods of DemoClass.
  16. 16. Pointcut Examples    execution(public int DemoClass.*(..)): This advice will be applied to the public methods of DemoClass and returning an int. execution(public int DemoClass.*(int, ..)): This advice will be applied to the public methods of DemoClass and returning an int and having first parameter as int. execution(public int DemoClass.*(int, int)): This advice will be applied to the public methods of DemoClass and returning an int and having both parameters as int.
  17. 17. Reusing Pointcut Expression @Pointcut("execution(* *.*(..))") private void loggingOperation() {} @Before("loggingOperation()") public void logBefore(JoinPoint joinPoint) {}
  18. 18. PointCut Class Aspect @Aspect Class PointCut { @Pointcut("execution(* *.*(..))") private void loggingOperation() {} }
  19. 19. @AfterReturning( pointcut = "PointCut.loggingOperation()", returning = "result") public void logAfterReturning(JoinPoint joinPoint, Object result) { }
  20. 20. Type Signature Pattern   Within - pointcut expressions matches all join points within certain types. pointcut matches all the method execution join points within the com.msoftgp.spring package within(com.msoftgp.spring.*)  To match the join points within a package and its subpackage, you have to add one more dot before the wildcard. within(com.msoftgp.spring..*)
  21. 21.  The pointcut expression matches the method execution join points within a particular class: within(com.msoftgp.spring.ArithmeticCalculatorImpl)  Again, if the target class is located in the same package as this aspect, the package name can be omitted. within(ArithmeticCalculatorImpl)
  22. 22.  You can match the method execution join points within all classes that implement the ArithmeticCalculator interface by adding a plus symbol. within(ArithmeticCalculator+)
  23. 23. Combining Pointcuts @Aspect public class CalculatorPointcuts { @Pointcut("within(ArithmeticCalculator+)") public void arithmeticOperation() {} @Pointcut("within(UnitCalculator+)") public void unitOperation() {} @Pointcut("arithmeticOperation()|| unitOperation()") public void loggingOperation() {} }
  24. 24. Pointcut Parameters   execution(* *.*(..)) && target(target) && args(a,b) Public void logBefore(Object target,int a,int b)
  25. 25. AOP Introduction  Special type of Advice  Same effect as multiple inheritance  Mechanism used – Dynamic Proxy  @DeclareParents
  26. 26. Load Time Weaving AspectJ  Purpose – Additional Pointcuts ,apply aspects to objects created outside the Spring IoC container    Weaving is the process of applying aspects to your target objects. Weaving happens at runtime through dynamic proxies. Supports compile time and load time weaving.
  27. 27. Types of AspectJ Weaving  Complie time weaving  Load time weaving    By AspectJ Weaver Spring Load time Weaver Application Used : Caching
  28. 28. Configuring AspectJ Aspects in Spring  Factory-method is aspectof()
  29. 29. Injecting Spring Beans into Domain Beans    Wiring Spring objects and Domain Objects Injection of Spring beans is a cross cutting concern Annotate the Domain class with @Configurable
  30. 30. THANK YOU

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