1. Aspect Oriented ProgrammingBy
Rohit Ghatol
&
Loukik Purohit

2. What is Aspect Oriented Programming?

3. Core Business Logic

4. Concerns Pooling Tracing Logging Caching Transactions Contract
Profiling

5. Problem Statement

6. Shopping Cart Operator
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 DAO
Shopping Cart DAO
Inventory Service
Shopping Service
Shopping Cart Operator
Logging
Security
Transactions
Caching
Pooling

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

10. AspectJ

11. Problem -1 Tracing/Logging

12. New Project
New Person
Logging/Tracing
Debugging Flow

13. Shopping Cart Operator
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. Shopping Cart Operator
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. Shopping Cart Operator
Connection Pooling
Inventory.jsp
Inventory Service
Inventory DAO 4
CartView.jsp
Shopping Cart Operator
Shopping Service
Shopping Cart DAO 4
View
Service
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
boolean equals();
Int hashcode();
Item
String getID();
String getName();
String getDescription();
Item clone();
String toString();
Referred as “Introduction” or ITD

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

25. HelloWorld AspectJ
Code Example

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

27. package com.test.aspects;
/**
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. ackage com.test.aspects;
/**
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

33. Flow Example InventoryService InventoryDAO JoinPoint
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 }
InventoryDAO
Item getItem(long id)
PointCut :execution(InventoryDAO.getItem(..))
PointCut :execution(*DAO.getItem(..))

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

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

36. Proxy Target Caller Only Method Pointcuts RUN TIME WEAVING 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 execution(* com.mypackage.myClass.method(..))
Trigger on method execution
Any Return type
Method Declaration
Takes any args

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

40. AspectJ Syntax

41. public aspect ExampleAspect {
Map<Long, Object> userIdMap = new HashMap<Long, Object>();
//Caching Point Cut
pointcut daoGetters(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");
return userIdMap.get(user.getUserId());
} else {
Object object = proceed(user);
System.out.println(" #Caching: Got ShoppingCart from Database - Expensive");
userIdMap.put(user.getUserId(), object);
return object; }
//…. Turn to next slide

42. public aspect ExampleAspect {……
//ITD / Introduction
public String ShopItem.toString(){
return "ShopItem [itemId=" + getItemId() + ", itemName=" + getItemName()
+ ", itemDescription=" + getItemDescription() + "]"; }
//Compiler Warnign and Errors
declare warning:get(* System.out):"Do not use System.out.println";
declare warning : (call(* com.test..*Dao.*(..)) &&
!within(com.test..*Service)):
"DAOs should only be called from Service layer";

43. Logging, Tracing & Profiling
Code Example

44. Pooling and Caching
Code Example

45. Spring AOP

46. Proxy Target Caller Only Method Pointcuts RUN TIME WEAVING 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 execution(* com.mypackage.myClass.method(..))
Trigger on method execution
Any Return type
Method Declaration
Takes any args

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

50. Introduction

51. Modelling Domain
Spring Context
Bean
Instantiate
Configure

52. Hibern-ate Modelling Domain Spring Context Bean Instantiates
Configures
Bean

53. <aop:spring-configured/>
Spring + AspectJ
<aop:spring-configured/>

54. Conclusion AspectJ Spring AOP
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
Less Powerful – only supports method level weaving
Runtime weaving strictly requires Spring
Easier to learn
Much slower than AspectJ
No such need