Aspect Oriented Programming

1. Aspect Oriented Programming By Rohit Ghatol & LoukikPurohit

2. What is Aspect Oriented Programming?

3. Core Business Logic

4. Pooling Tracing Logging Concerns Caching Transactions Contract Profiling

5. Problem Statement

6. Layered Architecture Inventory.jsp Inventory Service Inventory DAO CartView.jsp Shopping Cart Operator Shopping Service Shopping Cart DAO View Service Database

7. Non AOP Solution

8. Cross Cutting Concerns Inventory Service Logging Shopping Cart Operator Security Shopping Service Transactions Inventory DAO Caching Shopping Cart DAO Pooling

9. AOP Implementations AspectJ Spring AOP Works with runtime proxies which extend and wrap and delegate calls to original objects • Compile time changes the byte code of existing .class to inject new concerns in code

10. What is Weaving? Class B Class A1 Class A2 String getData() void method1() void method2()

11. What is Weaving? Class B Class A1 Class A2 String getData() void method1() void method2()

12. What is Weaving? Class B Class A1 Class A2 String getData() void method1() void method2() Proxy

13. AspectJ

14. Problem -1 Tracing/Logging

15. New Project New Person Logging/Tracing Debugging Flow

16. Logging/Tracing Inventory.jsp Inventory Service Inventory DAO L L L CartView.jsp Shopping Cart Operator L L Shopping Service Shopping Cart DAO L View Service Database

17. Problem -2 Profiling

19. Problem -3 Caching

20. Caching to avoid DB hit Inventory.jsp Inventory Service Inventory DAO Cache CartView.jsp Shopping Cart Operator Shopping Service Shopping Cart DAO Cache View Service Database

21. Problem -4 Connection Pooling

22. Connection Pooling Inventory.jsp Inventory Service Inventory DAO CartView.jsp Shopping Cart Operator 4 Shopping Service Shopping Cart DAO View Service 4 Database

23. Problem -5 Contracts

24. Use of System.out.println View calling DAO ……….

25. Problem -6 Adding to existing Classes

26. Extending without changing code Item String getID(); String getName(); String getDescription(); boolean equals(); Inthashcode(); Item clone(); String toString(); Referred as “Introduction” or ITD

27. AspectJ using STS Download from http://www.springsource.com/developer/sts

28. HelloWorldAspectJ Code Example

29. package com.test; /** * @author rohit * */ public class Helloworld { public static void main(String args[]){ Helloworldhelloworld = new Helloworld(); helloworld.hello(); } public void hello(){ System.out.print("Hello"); } } HelloWorld.java

30. package com.test.aspects; /** * @author rohit * */ public aspect WorldAspect { pointcut world() : call( public void com.test.Helloworld.hello()) ; before(): world(){ System.out.print("--> "); } after() : world() { System.out.print(" World!"); } } WorldAspect.java

31. ackagecom.test.aspects; /** * @author rohit * */ public aspect Decorator { declare precedence: Decorator, WorldAspect; pointcut world() : call(* *.hello(..)) && !within(Decorator) && !within(WorldAspect) ; void around(): world(){ System.out.print("**** "); proceed(); System.out.print(" ****"); } } Decorator.java

32. Output of Program **** --> Hello World! ****

33. AspectJ Process Main Java Source .Classes Business Logic .Classes AspectJ Compiler Business Logic with Concerns now weaved in Aspects Source

34. Different Types of Aspect Dynamic Cross Cutting Static Cross Cutting

35. Dynamic Cross Cutting Join Points Point Cut Advice Join Points Join Points

36. Flow Example JoinPoint InventoryService InventoryDAO Item getItem(long id) Item getItem(long id) Around Advice Psuedo Code If(item in cache){ return item; }else{ //fetch from db; proceed(); put item in cache; return item } PointCut :execution(InventoryDAO.getItem(..)) PointCut :execution(*DAO.getItem(..))

37. Writing pointcuts accessor return type execution(* com.mypackage.myClass.method(..)) Takes any args execution/ call/ new/ handler Method Declaration Reference : http://www.eclipse.org/aspectj/doc/released/progguide/quick.html

38. Static Cross Cutting Introduction/ITD Employee Inject equals() & hashCode() private String firstName; private String lastName; private long birthDate //…getters & setters() Inject persist() & merge() Inject implements Serializable

39. Static Cross Cutting Compile Type Declaration declare warning : get(* System.out): ”Use Logging Framework";

40. RUN TIME WEAVING Proxy Target Caller Pointcut Advice 1 Advice 2 Pointcut Only Method Pointcuts

41. Spring Proxy Generation Using java.lang.reflect.Proxy Class Using the CGLIB library

42. Writing pointcuts Any Return type execution(* com.mypackage.myClass.method(..)) Takes any args Trigger on method execution Method Declaration

43. Springs Advice Before Method Around After Returning Successful Return Exception After Throwing

44. AspectJ Syntax

45. public aspect ExampleAspect { Map<Long, Object> userIdMap = new HashMap<Long, Object>(); //Caching Point Cut pointcutdaoGetters(User user): execution(* com.test..*ShoppingCartDao.get*(..)) && args(user); Object around(User user) : daoGetters(user) { if (userIdMap.containsKey(user.getUserId())) { System.out.println(" #Caching: Got ShoppingCart from Cache - Cheap"); returnuserIdMap.get(user.getUserId()); } else { Object object = proceed(user); System.out.println(" #Caching: Got ShoppingCart from Database - Expensive"); userIdMap.put(user.getUserId(), object); returnobject; } } //…. Turn to next slide }

46. public aspect ExampleAspect { …… //ITD / Introduction public StringShopItem.toString(){ return "ShopItem [itemId=" + getItemId() + ", itemName=" + getItemName() + ", itemDescription=" + getItemDescription() + "]"; } //Compiler Warnign and Errors declarewarning:get(* System.out):"Do not useSystem.out.println"; declarewarning : (call(* com.test..*Dao.*(..)) && !within(com.test..*Service)): "DAOsshouldonlybecalled from Service layer"; }

47. Logging, Tracing & Profiling Code Example

48. Pooling and Caching Code Example

49. Spring AOP

50. RUN TIME WEAVING Proxy Target Caller Pointcut Advice 1 Advice 2 Pointcut Only Method Pointcuts