The document introduces aspect-oriented programming (AOP) using the Spring framework. AOP enables separating cross-cutting concerns like logging, caching, and error handling into modular aspects. Spring AOP uses dynamic proxies to advise Spring beans by adding aspects without modifying code. It provides an example of adding performance tracing to a service method using an aspect configured as a Spring bean.

1. A spect O riented P rogramming using Spring Framework Arseni Grigorjev arsenikum[gmail.com]

2. Me Server side Java (~5y) Aqris Software Online gambling

3. Simple service method public class SimpleService { … public List getCustomerOrders( long operatorId, long customerId) { List result; long start = System. currentTimeMillis(); if (!hasPermissions(operatorId)) { throw new NotAuthorizedException(); } try { ordersCache.getOrders(customerId); if (result == null ) { logger.info( "going to fetch orders for " + customerId); result = customerDao.getOrders(customerId); logger.info( "fetched orders for " + customerId + ": " + result); ordersCache.putOrders(customerId, result); } } catch (CusstomerNotFoundException e) { logger.error( "Customer " + customerId + " not found" , e); result = null ; } long end = System. currentTimeMillis(); logger.debug( "method took " + (end - start) + " ms" ); return result; } … } + authorization + error handling + performance monitoring + caching + logging

5. Aspect Oriented Programming A spect O riented P rogramming (AOP) enables modularization of cross-cutting concerns Separation of Concerns principle – no code tangling 1:1 principle – no code scattering

6. Cross-Cutting Concerns Examples Logging and Tracing Transaction Management Security Caching Error Handling Performance Monitoring Custom Business Rules

7. System Evolution: Conventional

8. How AOP Works Write your mainline application logic Write aspects to implement cross-cutting concerns Bind it all together

9. System Evolution: AOP Based

10. Leading AOP Technologies AspectJ 1995, original AOP technology Offers a full Aspect Oriented Programming language Modifies byte code to add aspects into your application!

11. Leading AOP Technologies (2) Spring AOP Uses dynamic proxies to add aspects into your application Only spring beans can be advised Uses some of AspectJ expression syntax

12. Core AOP Concepts Join Point A point of execution of a program such as method call or field assignment Pointcut An expression that selects one or more Join Points Advice Code to be executed at a Join Point that has been selected by a Pointcut Aspect A module that encapsulates Pointcuts and Advice

13. Spring AOP Example Business logic: public class SimpleService { … public List getCustomerOrders( long operatorId, long customerId) { return customerDao.getOrders(customerId); } … }

14. Spring AOP Example (2) Performance tracing aspect:

15. Spring AOP Example (3) Configure the Aspect as a Bean: <beans> <aop:aspectj-autoproxy> <aop:include name=“performanceTracer” /> </aop:aspectj-autoproxy> <bean id=“performanceTracer” class=“ com.foo.bar. PerformanceTracer ” /> </beans>

16. Advice Types @Around @Before @After @AfterReturning @AfterThrowing

17. SpringSource Tool Suite AOP Support

18. SpringSource Tools Suite AOP Support (2)

19. Useful Links Aspect Oriented Programming with Spring http://static.springsource.org/spring/docs/2.5.x/reference/aop.html Lots of examples Highlights on AspectJ syntax SpringSource Tool Suite: http://www.springsource.com/products/sts Eclipse IDE with Spring (and Spring AOP) support

20. Thank You! Questions?