Spring AOP简述

本文内容纲要:

- Key Terms

- Spring AOP的使用

- Aspect based

- 配置

- 编码

- Reference

使用面想对象(Object-Oriented Programming,OOP)包含一些弊端,当需要为多个不具有继承关系的对象引入公共行为时,例如日志,安全检测等。我们只有在每个对象中引入公共行为,这样程序中就产生了大量的代码,程序就不便于维护了,所以就有了一个面向对象编程的补充---面向切面编程(Aspect-Oriented Programming, AOP),AOP关注的方向是横向的,OOP关注的时纵向的;OOP中模块的基本单元是class,而AOP中基本的模块单元称作Aspect。

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AOP的其主要作用是,在不修改源代码的情况下给某个或者一组操作添加额外的功能。像日志记录,事务处理,权限控制等功能,都可以用AOP来“优雅”地实现,使这些额外功能和真正的业务逻辑分离开来,软件的结构将更加清晰。AOP是OOP的一个强有力的补充。

Key Terms

学习AOP,我们需要关注一些技术名词:

  1. Aspect: 切面,横向贯穿于多个类的某个服务,比如事务处理
  2. Join Point:又叫point cut,是指那些方法需要被执行"AOP"
  3. Advice:join point上特定的时刻执行的操作,Advice有几种不同类型,下文将会讨论(通俗地来讲就是起作用的内容和时间点)。
  4. Introduction: 给对象增加方法或者属性
  5. Target object: Advice起作用的对象
  6. AOP proxy:为实现AOP所实现的代理,在Spring中实现代理的方式有两种,JDK代理和CGLIB代理
  7. Weaving:将Advice织入join point的过程

Advice的类型:

  1. Before advice: 在执行join point之前执行
  2. After returning advice: 执行在join point这个方法返回之后的advice
  3. After throwing advice: 当方法抛出异常之后执行
  4. After (finally) advice: Advice在方法退出之后执行。
  5. Around advice: 包围一个连接点的通知,如方法调用。这是最 强大的通知。Aroud通知在方法调用前后完成自定义的行为。它们负责选择继续执行连接点或通过 返回它们自己的返回值或抛出异常来短路执行。

Spring AOP的使用

有三种方式使用Spring AOP,分别是:@Aspect-based(Annotation),Schema-based(XML),以及底层的Spring AOP API。其中@Aspect-based是使用最多的一种方式。我们所讲的例子也是基于@Aspect-based(Annotation)这种方式的

Aspect based

配置

Spring AOP Maven依赖

<dependency>

<groupId>org.springframework</groupId>

<artifactId>spring-context</artifactId>

<version>4.2.1.RELEASE</version>

</dependency>

<dependency>

<groupId>org.springframework</groupId>

<artifactId>spring-aop</artifactId>

<version>4.2.1.RELEASE</version>

</dependency>

<dependency>

<groupId>org.aspectj</groupId>

<artifactId>aspectjrt</artifactId>

<version>1.6.11</version>

</dependency>

<dependency>

<groupId>org.aspectj</groupId>

<artifactId>aspectjweaver</artifactId>

<version>1.8.7</version>

</dependency>

xml文件配置

<?xml version="1.0" encoding="UTF-8"?>

<beans xmlns="http://www.springframework.org/schema/beans" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"

xmlns:aop="http://www.springframework.org/schema/aop"

xsi:schemaLocation="http://www.springframework.org/schema/beans

http://www.springframework.org/schema/beans/spring-beans-3.1.xsd

http://www.springframework.org/schema/aop

http://www.springframework.org/schema/aop/spring-aop-3.1.xsd">

<!-- 使能AOP-->

<aop:aspectj-autoproxy/>

<!-- 声明一个切面-->

<bean id="myAspect" class="com.mj.spring.aop.MyAspect"></bean>

<!--声明AOP target-->

<bean id="userManager" class="com.mj.spring.aop.UserManager"></bean>

</beans>

编码

定义切面类

<!--定义切面类-->

@Aspect

public class MyAspect {

//定义切点, 这个切点的使用范围是: 定义在com.mj.spring.aop包下的所有方法

@Pointcut("execution(* com.mj.spring.aop.*.*(..))")

public void aPointcut() {

}

//定义Before Advice

@Before("aPointcut()")

public void beforeAdvice() {

System.out.println("before advice is executed!");

}

//定义AfterReturning Advice

@AfterReturning(pointcut = "aPointcut()", returning = "r")

public void afterReturningAdvice(String r) {

if (r != null)

System.out.println("after returning advice is executed! returning String is : " + r);

}

//定义After Advice

@After("aPointcut()")

public void AfterAdvice() {

System.out.println("after advice is executed!");

}

@After("aPointcut() && args(str)")

public void AfterAdviceWithArg(String str) {

System.out.println("after advice with arg is executed!arg is : " + str);

}

//定义afterThrowingAdvice Advice

@AfterThrowing(pointcut = "aPointcut()", throwing = "e")

public void afterThrowingAdvice(Exception e) {

System.out.println("after throwing advice is executed!exception msg is : " + e.getMessage());

}

//定义around advice

@Around(value="execution(public String com.mj.spring.aop.UserManager.getUser(..))")

public void aroundSayHello(ProceedingJoinPoint joinPoint) throws Throwable{

System.out.println("Around Before !! ");

joinPoint.proceed();

System.out.println("Around After !! ");

}

}

定义AOP target类

public class UserManager {

/*这个方法需要一个参数*/

public void addUser(String user) {

System.out.println("addUser(String str) method is executed!");

}

public void deleteUser() {

System.out.println("deleteUser() method is executed!");

}

/*这个方法返回一个字符串*/

public String getUser() {

System.out.println("getUser() method is executed!");

return "Hello";

}

/*这个方法抛出一个异常*/

public void editUser() throws Exception {

throw new Exception("something is wrong.");

}

}

测试类

public class UserManagerTest {

private ApplicationContext applicationContext=null;

@Before

public void setUp() throws Exception {

applicationContext=new ClassPathXmlApplicationContext("ApplicationContext.xml");

}

@Test

public void shoud_get_user_maneger_bean() throws Exception {

UserManager userManager = (UserManager) applicationContext.getBean("userManager");

assertThat(userManager!=null,is(true));

}

@Test

public void should_apply_before_advice_and_after_advice_and_after_advice_with_arg() throws Exception{

UserManager userManager = (UserManager) applicationContext.getBean("userManager");

userManager.addUser("Jun.Ma");

}

@Test

public void should_apply_before_advice_and_after_advice() throws Exception{

UserManager userManager = (UserManager) applicationContext.getBean("userManager");

userManager.deleteUser();

}

@Test

public void should_apply_before_advice_and_after_advice_and_after_throwing_advice() throws Exception{

UserManager userManager = (UserManager) applicationContext.getBean("userManager");

userManager.editUser();

}

@Test

public void should_apply_before_advice_and_after_advice_after_return_advice() throws Exception{

UserManager userManager = (UserManager) applicationContext.getBean("userManager");

userManager.getUser();

}

@Test

public void should_apply_around_advice_and_before_advice_and_after_advice_after_return_advice() throws Exception{

UserManager userManager = (UserManager) applicationContext.getBean("userManager");

userManager.getUser();

}

}

Reference

http://docs.spring.io/spring/docs/current/spring-framework-reference/htmlsingle/#aop-enable-aspectj-java Spring Document Reference

http://blog.psjay.com/posts/summary-of-spring-3-aop/ Spring AOP 3 Summary

源码git路径: git@github.com:jma19/spring.git

本文内容总结:Key Terms,Spring AOP的使用,Aspect based,配置,编码,Reference,

原文链接:https://www.cnblogs.com/jun-ma/p/4833539.html

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