在Spring 2.0中,除了传统的通过实现AOP AIP的方式来实现Advice之外,还提供了两种更加简便的方式来实现Advice:1)基于XML Schema的设置;2)基于Annotation的支持,采用这两种方式,Advice将不用实现特定的接口。现在让我们来看看如何使用这两种方式来分别实现Before Advice、After Advice、Around Advice、Throwing Advice。
一、Before Advice:基于XML Schema
当基于XML Schema实现Before Advice时,你的Advice类不用实现org.springframework.aop.MethodBeforeAdvice接口,例如:
java 代码
1. package com.savage.aop;
2.
3. import org.aspectj.lang.JoinPoint;
4.
5. public class LogBeforeAdvice {
6. public void before(JoinPoint joinPoint) {
7. System.out.println("Logging before " + joinPoint.getSignature().getName());
8. }
9. }
before方法是在目标对象上的方法被执行前要执行的方法,before方法中的JoinPoint参数是可选项,你可以根据需要决定是否需要JoinPoint参数,通过JoinPoint对象,你可以获得目标对象(getTarget())、目标方法上的参数(getArgs())等信息。
然后在XML中为目标对象指定LogBeforeAdvice代理:
xml 代码
1. <?xml version="1.0" encoding="UTF-8"?>
2. <beans xmlns="http://www.springframework.org/schema/beans"
3. xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
4. xmlns:aop="http://www.springframework.org/schema/aop"
5. xsi:schemaLocation="http://www.springframework.org/schema/beans
6. http://www.springframework.org/schema/beans/spring-beans-2.0.xsd
7. http://www.springframework.org/schema/aop
8. http://www.springframework.org/schema/aop/spring-aop-2.0.xsd">
9. <bean id="messageSender" class="com.savage.aop.HttpMessageSender"></bean>
10.
11. <bean id="logBeforeAdvice" class="com.savage.aop.LogBeforeAdvice"></bean>
12.
13. <aop:config>
14. <aop:aspect id="logBefore" ref="logBeforeAdvice">
15. <aop:before pointcut="execution(* com.savage.aop.MessageSender.*(..))"
16. method="before"/>
17. </aop:aspect>
18. </aop:config>
19. </beans>
如上所示,在Spring 2.0中要使用基于XML Sechma声明AOP的方式,需要在XML中加入aop的名称空间。当基于XML Sechma实现AOP时,所有的AOP都是在<aop:config></aop:config>标签中声明的,<aop:aspect></aop:aspect>用于定义Advice实例。<aop:before></aop:before>表示当前实例用于实现Before Advice;pointcut属性用于指定pointcut表示式,上面的例子表示此Advice将应用于com.savage.aop.MessageSender接口中的任何方法;method属性表示Advice上要调用的方法。
现在调用任何MessageSender接口上的方法之前都会执行LogBeforeAdvice的before方法,例如:
java 代码
1. package com.savage.aop;
2.
3. import org.springframework.context.ApplicationContext;
4. import org.springframework.context.support.ClassPathXmlApplicationContext;
5.
6. public class AdviceDemo {
7. public static void main(String[] args) {
8. ApplicationContext context =
9. new ClassPathXmlApplicationContext("beans-config.xml");
10. MessageSender sender = (MessageSender)context.getBean("messageSender");
11. sender.sendMessage("message");
12. }
13. }
二、Before Advice:基于Annotation
使用Annotation来实现Advice,在XML文件上的定义要比基于XML Sechema的方法要简便的多,但在实现Before Advice类时,则需要使用到@Aspect、@Before标识,并需要引入org.aspectj.lang.annotation包中的类。还以LogBeforeAdvice为例,LogBeforeAdvice类需要改为:
java 代码
1. package com.savage.aop;
2.
3. import org.aspectj.lang.JoinPoint;
4. import org.aspectj.lang.annotation.Aspect;
5. import org.aspectj.lang.annotation.Before;
6.
7. @Aspect
8. public class LogBeforeAdvice {
9. @Before("execution(* com.savage.aop.MessageSender.*(..))")
10. public void before(JoinPoint joinPoint) {
11. System.out.println("Logging before " + joinPoint.getSignature().getName());
12. }
13. }
如上所示,通过@Aspect将一个类声明为Aspect类,通过@Before将方法声明Before Advice,方法中的JoinPoint同样是可选的。然后在XML文件中做如下定义:
xml 代码
1. <?xml version="1.0" encoding="UTF-8"?>
2. <beans xmlns="http://www.springframework.org/schema/beans"
3. xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
4. xmlns:aop="http://www.springframework.org/schema/aop"
5. xsi:schemaLocation="http://www.springframework.org/schema/beans
6. http://www.springframework.org/schema/beans/spring-beans-2.0.xsd
7. http://www.springframework.org/schema/aop
8. http://www.springframework.org/schema/aop/spring-aop-2.0.xsd">
9. <bean id="messageSender" class="com.savage.aop.HttpMessageSender"></bean>
10.
11. <bean id="logBeforeAdvice" class="com.savage.aop.LogBeforeAdvice"></bean>
12.
13. <aop:aspectj-autoproxy/>
14. </beans>
所有基于Annotation实现的Advice,在XML文件中都只要使用<aop:aspectj-autoproxy></aop:aspectj-autoproxy>进行设置就可以了,非常简单。
三、After Advice:基于XML Sechma
和Before Advice一样,基于XML Sechma实现After Returning Advice时,不再需要org.springframework.aop.AfterReturningAdvice接口:
java 代码
1. package com.savage.aop;
2.
3. import org.aspectj.lang.JoinPoint;
4.
5. public class LogAfterReturningAdvice {
6. public void afterReturning(JoinPoint joinPoint) {
7. System.out.println("Logging after " + joinPoint.getSignature().getName());
8. }
9. }
然后在XML中做如下设置:
xml 代码
1. <?xml version="1.0" encoding="UTF-8"?>
2. <beans xmlns="http://www.springframework.org/schema/beans"
3. xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
4. xmlns:aop="http://www.springframework.org/schema/aop"
5. xsi:schemaLocation="http://www.springframework.org/schema/beans
6. http://www.springframework.org/schema/beans/spring-beans-2.0.xsd
7. http://www.springframework.org/schema/aop
8. http://www.springframework.org/schema/aop/spring-aop-2.0.xsd">
9. <bean id="messageSender" class="com.savage.aop.HttpMessageSender"></bean>
10.
11. <bean id="logAfterReturningAdvice"
12. class="com.savage.aop.LogAfterReturningAdvice"></bean>
13.
14. <aop:config>
15. <aop:aspect id="logAfterReturning" ref="logAfterReturningAdvice">
16. <aop:after-returning
17. pointcut="execution(* com.savage.aop.MessageSender.*(..))"
18. method="logAfterReturning"/>
19. </aop:aspect>
20. </aop:config>
21. </beans>
四、After Advice:基于Annotation
和Before Advice相似,使用@AfterReturning来表示After Returning Advice:
java 代码
1. package com.savage.aop;
2.
3. import org.aspectj.lang.JoinPoint;
4. import org.aspectj.lang.annotation.Aspect;
5. import org.aspectj.lang.annotation.AfterReturning;
6.
7. @Aspect
8. public class AfterReturningAdvice {
9. @AfterReturning(pointcut="execution(* com.savage.aop.MessageSender.*(..))",
10. returning="retVal")
11. public void afterReturning(JoinPoint joinPoint, Object retVal) {
12. System.out.println("Logging after " + joinPoint.getSignature().getName());
13. }
14. }
这里和Before Advice有点不同的是,在定义Poincut表示式时,多了一个returning属性,用于指定目标方法执行完后的返回值。
XML文件中的设置与LogBeforeAdvice的相似(将logBeforeAdvice的定义改为logAfterReturning的定义),不再列举。
五、Around Advice:基于XML Sechma
在Spring 2.0中,Around Advice不用实现org.aoplliance.intercept.MethodInterceptor接口,但Advice的方法必须返回对象,并且必须定义一个ProceedingJoinPoint参数,例如:
java 代码
1. package com.savage.aop;
2.
3. import org.aspectj.lang.ProceedingJoinPoint;
4.
5. public class LogAroundAdvice {
6. public void invoke(ProceedingJoinPoint joinPoint) {
7. System.out.println("Logging before " + joinPoint.getSignature().getName());
8. Object retVal = joinPoint.proceed();
9. System.out.println("Logging after " + joinPoint.getSignature().getName());
10. return retVal;
11. }
12. }
XML中的设置如下:
xml 代码
1. <?xml version="1.0" encoding="UTF-8"?>
2. <beans xmlns="http://www.springframework.org/schema/beans"
3. xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
4. xmlns:aop="http://www.springframework.org/schema/aop"
5. xsi:schemaLocation="http://www.springframework.org/schema/beans
6. http://www.springframework.org/schema/beans/spring-beans-2.0.xsd
7. http://www.springframework.org/schema/aop
8. http://www.springframework.org/schema/aop/spring-aop-2.0.xsd">
9. <bean id="messageSender" class="com.savage.aop.HttpMessageSender"></bean>
10.
11. <bean id="logAroundAdvice" class="com.savage.aop.LogAroundAdvice"></bean>
12.
13. <aop:config>
14. <aop:aspect id="logAround" ref="logAroundAdvice">
15. <aop:around
16. pointcut="execution(* com.savage.aop.MessageSender.*(..))"
17. method="invoke"/>
18. </aop:aspect>
19. </aop:config>
20. </beans>
六、Around Advice:基于Annotation
和Before Advice相似,使用@Around来表示Around Advice:
java 代码
1. package com.savage.aop;
2.
3. import org.aspectj.lang.ProceedingJoinPoint;
4. import org.aspectj.lang.annotation.Aspect;
5. import org.aspectj.lang.annotation.Around;
6.
7. @Aspect
8. public class AfterReturningAdvice {
9. @Around("execution(* com.savage.aop.MessageSender.*(..))")
10. public void invoke(ProceedingJoinPoint joinPoint) {
11. System.out.println("Logging before " + joinPoint.getSignature().getName());
12. Object retVal = joinPoint.proceed();
13. System.out.println("Logging after " + joinPoint.getSignature().getName());
14. return retVal;
15. }
16. }
XML文件中的设置与LogBeforeAdvice的相似(将logBeforeAdvice的定义改为logAroundAdvice的定义),不再列举。
七、Throw Advice:基于XML Sechma
在Spring 2.0中,Throw Advice不用实现org.springframework.aop.ThrowsAdvice接口,但Advice的方法必须定义Throwable(或其子类)参数,例如:
java 代码
1. package com.savage.aop;
2.
3. import org.aspectj.lang.JoinPoint;
4.
5. public class LogThrowingAdvice {
6. public void afterThrowing (JoinPoint joinPoint, Throwable throwable) {
7. System.out.println("Logging when throwing " + joinPoint.getSignature().getName());
8. }
9. }
在XML的设置如下:
xml 代码
1. <?xml version="1.0" encoding="UTF-8"?>
2. <beans xmlns="http://www.springframework.org/schema/beans"
3. xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
4. xmlns:aop="http://www.springframework.org/schema/aop"
5. xsi:schemaLocation="http://www.springframework.org/schema/beans
6. http://www.springframework.org/schema/beans/spring-beans-2.0.xsd
7. http://www.springframework.org/schema/aop
8. http://www.springframework.org/schema/aop/spring-aop-2.0.xsd">
9. <bean id="messageSender" class="com.savage.aop.HttpMessageSender"></bean>
10.
11. <bean id="logThrowingAdvice" class="com.savage.aop.LogThrowingAdvice"></bean>
12.
13. <aop:config>
14. <aop:aspect id="logThrowing" ref="logThrowingAdvice">
15. <aop:after-throwing
16. pointcut="execution(* com.savage.aop.MessageSender.*(..))"
17. throwing="throwable"
18. method="afterThrowing"/>
19. </aop:aspect>
20. </aop:config>
21. </beans>
在<aop:after-throwing></aop:after-throwing>中必须定义throwing属性,指定方法中的throwable参数。Spring将根据异常类型决定是否调用afterThrowing方法。
八、Throw Advice:基于Annotation
java 代码
1. package com.savage.aop;
2.
3. import org.aspectj.lang.JoinPoint;
4. import org.aspectj.lang.annotation.Aspect;
5. import org.aspectj.lang.annotation.AfterThrowing;
6.
7. @Aspect
8. public class AfterThrowingAdvice {
9. @AfterThrowing(pointcut="execution(* com.savage.aop.MessageSender.*(..))",
10. throwing="throwable")
11. public void afterThrowing(JoinPoint joinPoint, Throwable throwable) {
12. System.out.println("Logging when throwing "
13. + joinPoint.getSignature().getName());
14. }
15. }
XML文件中的设置与LogBeforeAdvice的相似(将logBeforeAdvice的定义改为logThrowingAdvice的定义),不再列举。
九、Pointcut
在Spring 2.0中,