The document discusses aspect-oriented programming (AOP) using Spring to modularize cross-cutting concerns like transaction management and logging. It provides examples of how logging and transaction code is duplicated across methods in a banking application. It then introduces AOP concepts like joinpoints, pointcuts, advice, and aspects to extract cross-cutting behavior into separate modules. Finally, it demonstrates how Spring AOP can be used to add login/logout advice around a customer's browsing method to track internet cafe usage.

1. AOP - Spring (Aspect Oriented Programming with Spring) Technical Knowledge Sharing Session 2

2. Common Functionalities used across the application modules Ex: Transaction management Logging Security Crosscutting Concerns

3. public void withdraw(int amount){ balance = this.balance – amount; accountDao.saveBalance(balance); } bankLogger.info(“Withdraw - ” + amount); txn.begin(); txn.commit(); public void deposit(int amount){ balance = this.balance + amount; accountDao.saveBalance(balance); } bankLogger.info(“Deposit - ” + amount); txn.begin(); txn.commit(); Crosscutting Concerns Eg: Banking Application Transaction Management Logging

4. public void withdraw(int amount){ balance = this.balance – amount; accountDao.saveBalance(balance); } public void deposit(int amount){ balance = this.balance + amount; accountDao.saveBalance(balance); } Coupling between Core & Crosscutting Concerns Duplicate Code Hard to maintain Code Why Worrying about Crosscutting Concerns? Logging bankLogger.info(“Withdraw - ” + amount); bankLogger.info(“Deposit - ” + amount); Transaction Management txn.begin(); txn.commit(); txn.begin(); txn.commit();

5. Transaction Management Logging public void withdraw(int amount){ balance = this.balance – amount; accountDao.saveBalance(balance); } public void deposit(int amount){ balance = this.balance + amount; accountDao.saveBalance(balance); } Any solution for Crosscutting Concerns? You can modularize Crosscutting Concerns Using Spring – AOP txn.begin(); txn.commit(); txn.begin(); txn.commit(); bankLogger.info(“Withdraw - ” + amount); bankLogger.info(“Deposit - ” + amount);

6. AOP will separate the Crosscutting concerns from the System What AOP Does?

7. withdraw deposit public void withdraw(int amount){ balance = this.balance – amount; accountDao.saveBalance(balance); } public void deposit(int amount){ balance = this.balance + amount; accountDao.saveBalance(balance); } Joinpoint Applying AOP Logging Transaction Management Advise

8. Joinpoint – Defines A Point During the Execution of a program. We can insert Additional logics at Joinpoints Advice – Action taken at a Joinpoint. Pointcut – Combination of Joinpoints where the Advice need to be Applied. Aspect – a modularization of a Crosscutting concern. AOP Concepts

9. Target object - object being advised by one or more aspects. AOP proxy – Will manage the way of Applying Aspects at particular Pointcuts. AOP Concepts Contd…

10. Action taken at a particular Joinpoint is called as an Advice Defines What needs to be Applied and When What – Functionality When – Advice Type Eg: Applying Logging Advice withdraw Advice

11. Before advice After returning advice After advice Around advice After throwing advice Method Method Method Method Method Exception Advice Types

12. Process of Applying Aspects to a Target Object. Will Create a proxied Object. AOP Weaving Class Bank{ public void withdraw(int amnt); } Proxy Target Caller

13. public class CustomerImpl implements Customer { public void browse (){ System.out.println(“ Browsing Internet ”); } } public class CafeOwner { public void loginTime (){ System.out.println(“ Login Time ”); } public void logoutTime (){ System.out.println(“ Logout Time ”); } public void issueBill (){ System.out.println(“ Calculate and issue the usage Bill ”); } } An Internet café owner wants a system to Issue an Usage bill and track the Login and Logout times at the end of Browsing Internet by A Customer. Example – Use of AOP with Spring

14. Output: Login Time Browsing Internet... Logout Time Example – Use of AOP with Spring Browse CafeOwner.loginTime () CafeOwner.logoutTime () Before Advice After Advice Pointcut

15. Reference Spring Documentation : Chapter 6. Aspect Oriented Programming with Spring Spring In Action – Manning (Updated for Spring 3.0) Video Tutorial – Spring AOP Tutorial

16. Thank you