AOP

AOP là gì?
tại sao phải học, phải dùng AOP?
"What is the purpose of object A?”
AOP này ra đời giải quyết vấn đề gì?
Áp dụng AOP vào những tình huống nào ?

9. Aspect Oriented Programming with Spring

9.1 Introduction
1. 9.1.1 AOP concepts
  - Aspect: a modularization of a concern that cuts across multiple classes. Transaction management is a good example of a crosscutting concern in enterprise Java applications. In Spring AOP, aspects are implemented using regular classes (the schema-based approach) or regular classes annotated with the @Aspect annotation (the @AspectJ style).
  - Join point: a point during the execution of a program, such as the execution of a method or the handling of an exception. In Spring AOP, a join point always represents a method execution.
  - Advice: action taken by an aspect at a particular join point. Different types of advice include "around," "before" and "after" advice. (Advice types are discussed below.) Many AOP frameworks, including Spring, model an advice as an interceptor, maintaining a chain of interceptors around the join point.
  - Pointcut: a predicate that matches join points. Advice is associated with a pointcut expression and runs at any join point matched by the pointcut (for example, the execution of a method with a certain name). The concept of join points as matched by pointcut expressions is central to AOP, and Spring uses the AspectJ pointcut expression language by default.
  - Introduction: declaring additional methods or fields on behalf of a type. Spring AOP allows you to introduce new interfaces (and a corresponding implementation) to any advised object. For example, you could use an introduction to make a bean implement an IsModified interface, to simplify caching. (An introduction is known as an inter-type declaration in the AspectJ community.)
  - Target object: object being advised by one or more aspects. Also referred to as the advised object. Since Spring AOP is implemented using runtime proxies, this object will always be a proxied object.
  - AOP proxy: an object created by the AOP framework in order to implement the aspect contracts (advise method executions and so on). In the Spring Framework, an AOP proxy will be a JDK dynamic proxy or a CGLIB proxy.
  - Weaving: linking aspects with other application types or objects to create an advised object. This can be done at compile time (using the AspectJ compiler, for example), load time, or at runtime. Spring AOP, like other pure Java AOP frameworks, performs weaving at runtime.
  Types of advice:
  - Before advice: Advice that executes before a join point, but which does not have the ability to prevent execution flow proceeding to the join point (unless it throws an exception).
  - After returning advice: Advice to be executed after a join point completes normally: for example, if a method returns without throwing an exception.
  - After throwing advice: Advice to be executed if a method exits by throwing an exception.
  - After (finally) advice: Advice to be executed regardless of the means by which a join point exits (normal or exceptional return).
  - Around advice: Advice that surrounds a join point such as a method invocation. This is the most powerful kind of advice. Around advice can perform custom behavior before and after the method invocation. It is also responsible for choosing whether to proceed to the join point or to shortcut the advised method execution by returning its own return value or throwing an exception.
  - Cross-Cutting Concerns: These are concerns that affect multiple parts of your application, like logging, security, or transactions.
  - Aspects: Aspects are modules that encapsulate cross-cutting concerns. They consist of advice and pointcuts.
  - Advice: Advice is the code that gets executed at specific join points.
  - Pointcuts: Pointcuts are expressions that define where advice should be applied.
  - Join Points: Join points are specific points in your application’s execution where advice can be applied.
2. 9.1.2 Spring AOP capabilities and goals
3. 9.1.3 AOP Proxies
AOP is used in the Spring Framework to...
- ... provide declarative enterprise services, especially as a replacement for EJB declarative services. The most important such service is declarative transaction management.
- ... allow users to implement custom aspects, complementing their use of OOP with AOP.
9.2 @AspectJ support
1. 9.2.1 Enabling @AspectJ Support
2. 9.2.2 Declaring an aspect
3. 9.2.3 Declaring a pointcut
4. 9.2.4 Declaring advice
  1. Before advice
  2. After returning advice
  3. After throwing advice
  4. After (finally) advice
  5. Around advice
  6. Advice parameters
  7. Access to the current JoinPoint
  8. Passing parameters to advice
  9. Advice parameters and generics
  10. Determining argument names
  11. Proceeding with arguments
  12. Advice ordering
5. 9.2.5 Introductions
6. 9.2.6 Aspect instantiation models
7. 9.2.7 Example
9.3 Schema-based AOP support
1. 9.3.1 Declaring an aspect
2. 9.3.2 Declaring a pointcut
3. 9.3.3 Declaring advice
  1. Before advice
  2. After returning advice
  3. After throwing advice
  4. After (finally) advice
  5. Around advice
  6. Advice parameters
4. 9.3.4 Introductions
5. 9.3.5 Aspect instantiation models
6. 9.3.6 Advisors
7. 9.3.7 Example
9.4 Choosing which AOP declaration style to use
1. 9.4.1 Spring AOP or full AspectJ?
2. 9.4.2 @AspectJ or XML for Spring AOP?
9.5 Mixing aspect types
9.6 Proxying mechanisms
1. 9.6.1 Understanding AOP proxies
9.7 Programmatic creation of @AspectJ Proxies
9.8 Using AspectJ with Spring applications
1. 9.8.1 Using AspectJ to dependency inject domain objects with Spring
  1. Unit testing @Configurable objects
  2. Working with multiple application contexts
2. 9.8.2 Other Spring aspects for AspectJ
3. 9.8.3 Configuring AspectJ aspects using Spring IoC
4. 9.8.4 Load-time weaving with AspectJ in the Spring Framework
9.9 Further Resources

AOP

9. Aspect Oriented Programming with Spring

10. Spring AOP APIs