在Spring 2.0中,除了傳統的通過實現AOP AIP的方式來實現Advice之外,還提供了兩種更加簡便的方式來實現Advice:1)基于XML Schema的設置;2)基于Annotation的支持,采用這兩種方式,Advice將不用實現特定的接口。現在讓我們來看看如何使用這兩種方式來分別實現Before Advice、After Advice、Around Advice、Throwing Advice。
一、Before Advice:基于XML Schema
當基于XML Schema實現Before Advice時,你的Advice類不用實現org.springframework.aop.MethodBeforeAdvice接口,例如:
java 代碼
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方法是在目標對象上的方法被執行前要執行的方法,before方法中的JoinPoint參數是可選項,你可以根據需要決定是否需要JoinPoint參數,通過JoinPoint對象,你可以獲得目標對象(getTarget())、目標方法上的參數(getArgs())等信息。
然后在XML中為目標對象指定LogBeforeAdvice代理:
xml 代碼
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聲明AOP的方式,需要在XML中加入aop的名稱空間。當基于XML Sechma實現AOP時,所有的AOP都是在<aop:config></aop:config>標簽中聲明的,<aop:aspect></aop:aspect>用于定義Advice實例。<aop:before></aop:before>表示當前實例用于實現Before Advice;pointcut屬性用于指定pointcut表示式,上面的例子表示此Advice將應用于com.savage.aop.MessageSender接口中的任何方法;method屬性表示Advice上要調用的方法。
現在調用任何MessageSender接口上的方法之前都會執行LogBeforeAdvice的before方法,例如:
java 代碼
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來實現Advice,在XML文件上的定義要比基于XML Sechema的方法要簡便的多,但在實現Before Advice類時,則需要使用到@Aspect、@Before標識,并需要引入org.aspectj.lang.annotation包中的類。還以LogBeforeAdvice為例,LogBeforeAdvice類需要改為:
java 代碼
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,通過@Aspect將一個類聲明為Aspect類,通過@Before將方法聲明Before Advice,方法中的JoinPoint同樣是可選的。然后在XML文件中做如下定義:
xml 代碼
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實現的Advice,在XML文件中都只要使用<aop:aspectj-autoproxy></aop:aspectj-autoproxy>進行設置就可以了,非常簡單。
三、After Advice:基于XML Sechma
和Before Advice一樣,基于XML Sechma實現After Returning Advice時,不再需要org.springframework.aop.AfterReturningAdvice接口:
java 代碼
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中做如下設置:
xml 代碼
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來表示After Returning Advice:
java 代碼
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. }
這里和Before Advice有點不同的是,在定義Poincut表示式時,多了一個returning屬性,用于指定目標方法執行完后的返回值。
XML文件中的設置與LogBeforeAdvice的相似(將logBeforeAdvice的定義改為logAfterReturning的定義),不再列舉。
五、Around Advice:基于XML Sechma
在Spring 2.0中,Around Advice不用實現org.aoplliance.intercept.MethodInterceptor接口,但Advice的方法必須返回對象,并且必須定義一個ProceedingJoinPoint參數,例如:
java 代碼
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中的設置如下:
xml 代碼
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來表示Around Advice:
java 代碼
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文件中的設置與LogBeforeAdvice的相似(將logBeforeAdvice的定義改為logAroundAdvice的定義),不再列舉。
七、Throw Advice:基于XML Sechma
在Spring 2.0中,Throw Advice不用實現org.springframework.aop.ThrowsAdvice接口,但Advice的方法必須定義Throwable(或其子類)參數,例如:
java 代碼
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的設置如下:
xml 代碼
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>中必須定義throwing屬性,指定方法中的throwable參數。Spring將根據異常類型決定是否調用afterThrowing方法。
八、Throw Advice:基于Annotation
java 代碼
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文件中的設置與LogBeforeAdvice的相似(將logBeforeAdvice的定義改為logThrowingAdvice的定義),不再列舉。
九、Pointcut
在Spring 2.0中,