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. AspectJ

11. Problem -1 Tracing/Logging

12. New Project New Person Logging/Tracing Debugging Flow

13. 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

14. Problem -2 Profiling

16. Problem -3 Caching

17. 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

18. Problem -4 Connection Pooling

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

20. Problem -5 Contracts

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

22. Problem -6 Adding to existing Classes

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

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

25. HelloWorldAspectJ Code Example

26. 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

27. 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

28. 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

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

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

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

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

33. 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(..))

34. 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

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

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

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

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

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

40. AspectJ Syntax

41. 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 }

42. 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"; }

43. Logging, Tracing & Profiling Code Example

44. Pooling and Caching Code Example

45. Spring AOP

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

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

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

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

50. Conclusion AspectJ Spring AOP Less Powerful – only supports method level weaving Runtime weaving strictly requires Spring Easier to learn Much slower than AspectJ No such need • More Powerful – methods, fields, constructor, aspect, field weaving • Compile time weaving – works with likes of Android • Learning curve is more • Much better in speed • Needs special compiler