Spring面向切面编程 AOP，实现AOP注解和XML配置的小例子

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本文深入解析面向切面编程（AOP）的概念与原理，介绍AOP在Spring框架中的应用，包括通知、切点、切面等关键术语，以及如何通过@AspectJ注解和XML配置实现AOP功能。

什么是面向切面编程？

	一个完整的程序，包括开始的启动日志，中间的业务逻辑实现，结尾的结束日志。
那么面向切面编程就是把业务逻辑实现作为一个切面，围绕这个切面编程。

AOP术语

	- 通知（advice）：定义了切面是什么以及何时使用。
			·前置通知(Before):在目标方法被调用之前调用通知功能；
			·后置通知(After)：在目标方法完成之后调用通知，此时不会关心方法的输出是什么。
			·返回通知(After-returning)：在目标方法成功执行之后调用通知。
			·异常通知(After-throwing)：在目标方法抛出异常后调用通知。
			·环绕通知 (Around)：通知包裹了被通知的方法，在被通知的方法调用之前和	调用之后执行自定义方法
	- 连接点（join point）：是在应用执行过程中能够插入切面的一个点，例如：调用方法，抛出异常，修改字段等。
	- 切点（Pointcut）：通常使用明确的类和方法名称，或正则表达式匹配的类和方法名称。通知定义了切面的“什么”和“何时”的话，切点就定义了“何处”
	- 切面（Aspect）：通知和切点共同定义了切面的全部内容--他是什么，在何时和何处完成其功能。
	- 引入（Introduction）：允许向现有的类添加新方法或属性。
	- 织入（Weaving）：织入的三个时期：编译期，类加载期，运行期。

Spring对AOP的支持

Spring提供了4种类型的AOP支持：

基于代理的经典Spring AOP；
纯POJO切面；
@AspectJ注解驱动的页面；
注入式AspectJ切面（适用于Spring各版本）；
前三种都是Spring AOP的变种，Spring AOP构建在动态代理基础之上，因此，Spring对AOP的支持局限于方法拦截。
Spring AOP的配置繁琐，功能局限。所以推荐适用AspectJ来实现AOP功能。

下面展示@AspectJ注解驱动的页面的实现：
使用注解的方式：

package aop;

public interface IPerformance {
	public void perform();
}

package aop;

import org.springframework.stereotype.Component;

@Component
public class Performance implements IPerformance{
	@Override
	public void perform() {
		System.out.println("表演开始");
	}
}

package aop;

import org.aspectj.lang.ProceedingJoinPoint;
import org.aspectj.lang.annotation.After;
import org.aspectj.lang.annotation.AfterThrowing;
import org.aspectj.lang.annotation.Around;
import org.aspectj.lang.annotation.Aspect;
import org.aspectj.lang.annotation.Before;
import org.aspectj.lang.annotation.Pointcut;
import org.springframework.stereotype.Component;

@Aspect
@Component
public class Audience {
	@Pointcut("execution(* *.perform(..))")
	public void perform() {}
	
	@Before("perform()")
	public void silenceCellPhone() {
		System.out.println("Silencing Cell Phone");
	}
	
	@Before("perform()")
	public void takeSeats() {
		System.out.println("Taking Seats");
	}
	
	@After("perform()")
	public void applause() {
		System.out.println("CLAP CLAP CLAP");
	}
	
	@AfterThrowing("perform()")
	public void demandRefund() {
		System.out.println("Demanding a refund");
	}
	
	@Around("perform()")
	public void around(ProceedingJoinPoint pjp) throws Throwable {
		System.out.println("环绕通知开始");
		pjp.proceed();
		System.out.println("环绕通知结束");
	}
}

package aop;

import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.ApplicationContext;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;
import org.springframework.test.context.ContextConfiguration;
import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;

@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration(classes=aop.AOPConfig.class)
public class AopTest {
	@Autowired
	IPerformance perform;
	@Test
	public void test() {
		perform.perform();
	}
	
	public static void main(String[] args) {
	     ApplicationContext ac = new AnnotationConfigApplicationContext("aop");
	     IPerformance perfomance = (IPerformance) ac.getBean("performance");
	     perfomance.perform()；
	}
}

测试类写了2中实现测试的方法，选择其中一个就可以了。

使用XML实现的方式，如下：

package aop;

public interface IPerformance {
	public void perform();
}

package aop;

public class Performance implements IPerformance{
	@Override
	public void perform() {
		System.out.println("表演开始");
	}
}

package aop;

import org.aspectj.lang.ProceedingJoinPoint;

public class Audience {
	public void silenceCellPhone() {
		System.out.println("Silencing Cell Phone");
	}
	
	public void takeSeats() {
		System.out.println("Taking Seats");
	}
	
	public void applause() {
		System.out.println("CLAP CLAP CLAP");
	}
	
	public void demandRefund() {
		System.out.println("Demanding a refund");
	}
	
	public void around(ProceedingJoinPoint pjp) throws Throwable {
		System.out.println("环绕通知开始");
		pjp.proceed();
		System.out.println("环绕通知结束");
	}
}

package aop;

import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;


public class AopXmlTest {
	public static void main(String[] args) {
	     ApplicationContext ac = new ClassPathXmlApplicationContext("ApplicationContext.xml");
	     IPerformance performance = (IPerformance) ac.getBean("performance");
	     performance.perform();
	}
}

ApplicationContext.xml有2中配置AOP的方式如下：

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
	xmlns:context="http://www.springframework.org/schema/context"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xmlns:aop="http://www.springframework.org/schema/aop"
    xmlns:tx="http://www.springframework.org/schema/tx"
    xsi:schemaLocation="
    	http://www.springframework.org/schema/beans
        http://www.springframework.org/schema/beans/spring-beans.xsd
        http://www.springframework.org/schema/aop
        http://www.springframework.org/schema/aop/spring-aop.xsd
        http://www.springframework.org/schema/tx
        http://www.springframework.org/schema/aop/spring-tx.xsd
        http://www.springframework.org/schema/context
        http://www.springframework.org/schema/context/spring-context.xsd
        ">
	<!-- 启动对@AspectJ注解的支持 -->
	<aop:aspectj-autoproxy/>
    <bean id="audience" class="aop.Audience">   
    </bean>
    
    <bean id="performance" class="aop.Performance">   
    </bean>

	<context:component-scan base-package="aop"/>
    <!-- more bean definitions go here -->
    <aop:config>
    	<aop:aspect ref="audience">
    		<!-- <aop:pointcut id="performance" expression="execution(* *.perform(..))"/> -->
    		<aop:before pointcut="execution(* *.perform(..))"
    		method="silenceCellPhone"/>
    		<aop:before pointcut="execution(* *.perform(..))"
    		method="takeSeats"/>
    		<aop:after pointcut="execution(* *.perform(..))"
    		method="applause"/>
    		<aop:after-throwing pointcut="execution(* *.perform(..))"
    		method="demandRefund"/>
    		<aop:around pointcut="execution(* *.perform(..))"
    		method="around"/>
    	</aop:aspect>
    </aop:config>
	
</beans>

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
	xmlns:context="http://www.springframework.org/schema/context"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xmlns:aop="http://www.springframework.org/schema/aop"
    xmlns:tx="http://www.springframework.org/schema/tx"
    xsi:schemaLocation="
    	http://www.springframework.org/schema/beans
        http://www.springframework.org/schema/beans/spring-beans.xsd
        http://www.springframework.org/schema/aop
        http://www.springframework.org/schema/aop/spring-aop.xsd
        http://www.springframework.org/schema/tx
        http://www.springframework.org/schema/aop/spring-tx.xsd
        http://www.springframework.org/schema/context
        http://www.springframework.org/schema/context/spring-context.xsd
        ">
	<!-- 启动对@AspectJ注解的支持 -->
	<aop:aspectj-autoproxy/>
    <bean id="audience" class="aop.Audience">   
    </bean>
    
    <bean id="performance" class="aop.Performance">   
    </bean>

	<!-- <context:component-scan base-package="aop"/> -->
    <!-- more bean definitions go here -->
    <aop:config>
    	<aop:aspect ref="audience">
    		<!-- 注意这里的切点ID不要和上面的bean的ID相同，不然会引起下面引用的冲突报错 -->
    		<aop:pointcut id="perform" expression="execution(* *.perform(..))"/>
    		<aop:before pointcut-ref="perform" method="silenceCellPhone"/>
    		<aop:before pointcut-ref="perform" method="takeSeats"/>
    		<aop:after pointcut-ref="perform"  method="applause"/>
    		<aop:after-throwing pointcut-ref="perform" method="demandRefund"/>
    		<aop:around pointcut-ref="perform" method="around"/>
    	</aop:aspect>
    </aop:config>
	
</beans>

pom.xml 这里用的很多不用的类，根据个人需要删减

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd">
  <modelVersion>4.0.0</modelVersion>
  <groupId>com.liangyu.aop</groupId>
  <artifactId>aopDemo</artifactId>
  <packaging>war</packaging>
  <version>0.0.1-SNAPSHOT</version>
  <name>aopDemo Maven Webapp</name>
  <url>http://maven.apache.org</url>
  <dependencies>
  	<dependency>
	    <groupId>org.springframework</groupId>
	    <artifactId>spring-aop</artifactId>
	    <version>5.1.5.RELEASE</version>
	</dependency>
	
	<dependency>
	    <groupId>org.springframework</groupId>
	    <artifactId>spring-aspects</artifactId>
	    <version>5.1.5.RELEASE</version>
	</dependency>
	
	<!-- https://mvnrepository.com/artifact/org.aspectj/aspectjweaver -->
	<dependency>
	    <groupId>org.aspectj</groupId>
	    <artifactId>aspectjweaver</artifactId>
	    <version>1.9.2</version>
	</dependency>
	
	<!-- https://mvnrepository.com/artifact/org.aspectj/aspectjrt -->
	<dependency>
	    <groupId>org.aspectj</groupId>
	    <artifactId>aspectjrt</artifactId>
	    <version>1.9.2</version>
	</dependency>
	
	<dependency>
	    <groupId>org.springframework</groupId>
	    <artifactId>spring-beans</artifactId>
	    <version>5.1.5.RELEASE</version>
	</dependency>
	
	<dependency>
	    <groupId>org.springframework</groupId>
	    <artifactId>spring-context</artifactId>
	    <version>5.1.5.RELEASE</version>
	    <type>pom</type>
	</dependency>
	
	<dependency>
	    <groupId>org.springframework</groupId>
	    <artifactId>spring-core</artifactId>
	    <version>5.1.5.RELEASE</version>
	    <type>pom</type>
	</dependency>
	
	<dependency>
	    <groupId>org.springframework</groupId>
	    <artifactId>spring-expression</artifactId>
	    <version>5.1.5.RELEASE</version>
	    <type>pom</type>
	</dependency>
	
	<dependency>
	    <groupId>org.springframework</groupId>
	    <artifactId>spring-tx</artifactId>
	    <version>5.1.5.RELEASE</version>
	    <type>pom</type>
	</dependency>
	
	
	<dependency>
	    <groupId>org.springframework</groupId>
	    <artifactId>spring-web</artifactId>
	    <version>5.1.5.RELEASE</version>
	    <type>pom</type>
	</dependency>
	
	<dependency>
	    <groupId>org.springframework</groupId>
	    <artifactId>spring-webmvc</artifactId>
	    <version>5.1.5.RELEASE</version>
	    <type>pom</type>
	</dependency>
	
	<dependency>
	    <groupId>org.springframework</groupId>
	    <artifactId>spring-test</artifactId>
	    <version>5.1.4.RELEASE</version>
	    <type>pom</type>
	</dependency>
	
	<!-- https://mvnrepository.com/artifact/org.apache.commons/commons-collections4 -->
	<dependency>
	    <groupId>org.apache.commons</groupId>
	    <artifactId>commons-collections4</artifactId>
	    <version>4.3</version>
	</dependency>
	
	<!-- https://mvnrepository.com/artifact/commons-logging/commons-logging -->
	<dependency>
	    <groupId>commons-logging</groupId>
	    <artifactId>commons-logging</artifactId>
	    <version>1.2</version>
	</dependency>
	
	<!-- https://mvnrepository.com/artifact/cglib/cglib-nodep -->
	<dependency>
	    <groupId>cglib</groupId>
	    <artifactId>cglib-nodep</artifactId>
	    <version>3.2.10</version>
	</dependency>

	<!-- https://mvnrepository.com/artifact/aopalliance/aopalliance -->
	<dependency>
	    <groupId>aopalliance</groupId>
	    <artifactId>aopalliance</artifactId>
	    <version>1.0</version>
	</dependency>				
	
	<!-- https://mvnrepository.com/artifact/org.apache.commons/commons-dbcp2 -->
	<dependency>
	    <groupId>org.apache.commons</groupId>
	    <artifactId>commons-dbcp2</artifactId>
	    <version>2.6.0</version>
	</dependency>
	
	<!-- https://mvnrepository.com/artifact/junit/junit -->
	<dependency>
	    <groupId>junit</groupId>
	    <artifactId>junit</artifactId>
	    <version>4.12</version>
	    <scope>test</scope>
	</dependency>

  </dependencies>
  <build>
    <finalName>aopDemo</finalName>
  </build>
</project>

运行结果如下：

Silencing Cell Phone
Taking Seats
环绕通知开始
表演开始
环绕通知结束
CLAP CLAP CLAP