spring框架——XML配置AOP

1 前言

在 AspectJ動態代理實現AOP 中，筆者介紹了使用 AspectJ 動態代理實現 AOP，本文將介紹使用 xml 文件配置AOP。

在 xml 文件中，可以使用 aop:config 標籤配置 AOP，常用的屬性如下：

• aop:aspect：配置切面
• aop:pointcut：配置切入點
• aop:before：前置通知，作用於方法執行之前
• aop:after：後置通知，作用於方法的finally語句塊，即不管方法有沒有異常都會執行，通常用於關閉資源
• aop:after-returning：返回通知，作用於方法執行之後
• aop:after-throwing：異常通知，作用於方法拋出異常時
• aop:around：環繞通知

注意：要想讓 IOC 容器管理切面，還需要給切面和被代理類標註 @Component，其用法見通過註解配置bean

需要導入的包如下：

其中，com 開頭的包爲 AspectJ 動態代理核心包，下載如下：

 com.springsource.net.sf.cglib-2.2.0、com.springsource.org.aopalliance-1.0.0、com.springsource.org.aspectj.weaver-1.7.2.RELEASE
 

2 案例

2.1 前置通知、後置通知、返回通知、異常通知

Comp.java

package com.compute;
 
public interface Comp {
	public int add(int a,int b);
	public int div(int a,int b);
}

CompImp.java

package com.compute;
 
import org.springframework.stereotype.Component;
 
@Component
public class CompImp implements Comp{
 
	@Override
	public int add(int a, int b) {
		return a+b;
	}
 
	@Override
	public int div(int a, int b) {
		return a/b;
	}
}

注意：CompImp 類前加 @Component 註解，是爲了將 bean 交給 IOC 容器管理 

Logger.java

package com.compute;

import java.util.Arrays;
import org.aspectj.lang.JoinPoint;
import org.springframework.stereotype.Component;

@Component
public class Logger {
	
	public void beforeMethod(JoinPoint joinPoint) {
		Object[] args=joinPoint.getArgs();
		String methodName=joinPoint.getSignature().getName();
		System.out.println("前置通知：method:"+methodName+", args:"+Arrays.toString(args));
	}
	
	public void afterMethod() {
		System.out.println("後置通知");
	}
	
	public void afterReturning(JoinPoint joinPoint,Object result) {
		String methodName=joinPoint.getSignature().getName();
		System.out.println("返回通知：method:"+methodName+", result:"+result);
	}
	
	public void afterThrowing(Exception e) {
		System.out.println("異常通知："+e);
	}
}

 注意：Logger 類前加 @Component 註解，是爲了將 bean 交給 IOC 容器管理 

comp.xml 

<?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"
	xmlns:context="http://www.springframework.org/schema/context"
	xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd
		http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-4.0.xsd
		http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop-4.0.xsd">
	<context:component-scan base-package="com.compute"></context:component-scan>
	<aop:config>
		<aop:aspect ref="logger">
			<aop:before method="beforeMethod" pointcut="execution(* com.compute.*.*(..))"/>
			<aop:after method="afterMethod" pointcut="execution(* com.compute.*.*(..))"/>
			<aop:after-returning method="afterReturning" pointcut="execution(* com.compute.*.*(..))" returning="result"/>
			<aop:after-throwing method="afterThrowing" pointcut="execution(* com.compute.*.*(..))" throwing="e"/>
		</aop:aspect>
	</aop:config>
</beans>

注意：需要導入 context 和 aop 命名空間，context:component-scan 用於掃描組件，即對標有 @Compnent 的類生成 bean 交給 IOC 容器管理；aop:config 用於配置 AOP。

Test.java

package com.compute;

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

public class Test {
	public static void main(String[] args) {
		ApplicationContext ac=new ClassPathXmlApplicationContext("comp.xml");
		Comp comp=ac.getBean("compImp",Comp.class);
		System.out.println(comp.getClass().getName()); //打印代理類的類名
		int result=comp.add(1,2);
		System.out.println(result);
		result=comp.div(2,0);
		System.out.println(result);
	}
}

運行結果：

com.sun.proxy.$Proxy7
前置通知：method:add, args:[1, 2]
後置通知
返回通知：method:add, result:3
3
前置通知：method:div, args:[2, 0]
後置通知
異常通知：java.lang.ArithmeticException: / by zero

拓展延伸

當有很多通知作用於同一切入點時，可以通過 aop:pointcut 指定公共切入點，如下：

comp.xml 

<?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"
	xmlns:context="http://www.springframework.org/schema/context"
	xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd
		http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-4.0.xsd
		http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop-4.0.xsd">
	<context:component-scan base-package="com.compute"></context:component-scan>
	<aop:config>
		<aop:aspect ref="logger">
			<aop:pointcut expression="execution(* com.compute.*.*(..))" id="pcut"/>
			<aop:before method="beforeMethod" pointcut-ref="pcut"/>
			<aop:after method="afterMethod" pointcut-ref="pcut"/>
			<aop:after-returning method="afterReturning" pointcut-ref="pcut" returning="result"/>
			<aop:after-throwing method="afterThrowing" pointcut-ref="pcut" throwing="e"/>
		</aop:aspect>
	</aop:config>
</beans>

2.2 環繞通知

本節僅介紹 Logger.java 和 comp.xml，其他類見2.1節

Logger.java

package com.compute;

import org.aspectj.lang.ProceedingJoinPoint;
import org.springframework.stereotype.Component;

@Component
public class Logger {
	
	public Object aroundMethod(ProceedingJoinPoint joinPoint) {
		Object result=null;
		try {
			System.out.println("前置通知");
			result=joinPoint.proceed(); //執行方法
			System.out.println("返回通知");
			return result;
		} catch (Throwable e) {
			System.out.println("異常通知");
			e.printStackTrace();
		}finally {
			System.out.println("後置通知");
		}
		return -1;
	}
}

 comp.xml 

<?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"
	xmlns:context="http://www.springframework.org/schema/context"
	xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd
		http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-4.0.xsd
		http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop-4.0.xsd">
	<context:component-scan base-package="com.compute"></context:component-scan>
	<aop:config>
		<aop:aspect ref="logger">
			<aop:around method="aroundMethod" pointcut="execution(* com.compute.*.*(..))"/>
		</aop:aspect>
	</aop:config>
</beans>

 運行結果：

com.sun.proxy.$Proxy7
前置通知
返回通知
後置通知
3
前置通知
異常通知
java.lang.ArithmeticException: / by zero
	at com.compute.CompImp.div(CompImp.java:15)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
	at java.lang.reflect.Method.invoke(Unknown Source)
	at org.springframework.aop.support.AopUtils.invokeJoinpointUsingReflection(AopUtils.java:317)
	at org.springframework.aop.framework.ReflectiveMethodInvocation.invokeJoinpoint(ReflectiveMethodInvocation.java:190)
	at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:157)
	at org.springframework.aop.aspectj.MethodInvocationProceedingJoinPoint.proceed(MethodInvocationProceedingJoinPoint.java:85)
	at com.compute.Logger.aroundMethod(Logger.java:13)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
	at java.lang.reflect.Method.invoke(Unknown Source)
	at org.springframework.aop.aspectj.AbstractAspectJAdvice.invokeAdviceMethodWithGivenArgs(AbstractAspectJAdvice.java:621)
	at org.springframework.aop.aspectj.AbstractAspectJAdvice.invokeAdviceMethod(AbstractAspectJAdvice.java:610)
	at org.springframework.aop.aspectj.AspectJAroundAdvice.invoke(AspectJAroundAdvice.java:68)
	at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179)
	at org.springframework.aop.interceptor.ExposeInvocationInterceptor.invoke(ExposeInvocationInterceptor.java:92)
	at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179)
	at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:207)
	at com.sun.proxy.$Proxy7.div(Unknown Source)
	at com.compute.Test.main(Test.java:13)
後置通知
-1

2.3 切面優先級

當有多個切面時，可以通過 aop:aspect 標籤的 order 屬性定義切面的優先級。

本節僅介紹LoggerA.java、LoggerB.java、comp.xml 以及 Test.java，Comp.java、CompImp.java見2.1節。

LoggerA.java

package com.compute;

import org.springframework.stereotype.Component;

@Component
public class LoggerA {
	
	public void beforeMethod() {
		System.out.println("前置通知:LoggerA");
	}
}

LoggerB.java

package com.compute;

import org.springframework.stereotype.Component;

@Component
public class LoggerB {
	
	public void beforeMethod() {
		System.out.println("前置通知:LoggerA");
	}
}

comp.xml

<?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"
	xmlns:context="http://www.springframework.org/schema/context"
	xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd
		http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-4.0.xsd
		http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop-4.0.xsd">
	<context:component-scan base-package="com.compute"></context:component-scan>
	<aop:config>
		<aop:aspect ref="loggerA" order="2">
			<aop:before method="beforeMethod" pointcut="execution(* com.compute.*.*(..))"/>
		</aop:aspect>
		<aop:aspect ref="loggerB" order="1">
			<aop:before method="beforeMethod" pointcut="execution(* com.compute.*.*(..))"/>
		</aop:aspect>
	</aop:config>
</beans>

Test.java

package com.compute;

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

public class Test {
	public static void main(String[] args) {
		ApplicationContext ac=new ClassPathXmlApplicationContext("comp.xml");
		Comp comp=ac.getBean("compImp",Comp.class);
		int result=comp.add(1,2);
		System.out.println(result);
	}
}

運行結果：

前置通知:LoggerB
前置通知:LoggerA
3