Spring事务管理用AOP实现,这里列一下APO的基本概念,AOP是建立在OOP基础上对类的行为进行归类后,形成的另一种理解程序结构的方法。以下内容摘自Spring官方文档。其中切面、连接点、通知、切入点的概念比较重要,可自己根据英文解释理解。连接点是程序执行的点,表示一个执行的方法,切入点是根据条件对连接点进行的筛选匹配,为保证原汁原味,下面附上原文

AOP concepts

Aspect: a modularization of a concern that cuts across multiple classes. Transaction management isa good example of a crosscutting concern in enterprise Java applications. In Spring AOP, aspectsare 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.

通知类型主要是根据连接点的执行和异常抛出情况执行通知, Before advice 在连接点执行之前执行,After returning advice 在连接点正常返回后执,After throwing advice则是在异常抛出后执行,After (finally) advice 是连接点执行后无论异常与否都会执行,Around advice是在连接点执行前和执行后都会执行,Spring 建议根据需求选择合适的最简单的通知类型。