本文講述使用AspectJ框架實現(xiàn)Spring AOP。

再重復一下Spring AOP中的三個概念，

Advice：向程序內(nèi)部注入的代碼。

Pointcut：注入Advice的位置，切入點，一般為某方法。

Advisor：Advice和Pointcut的結(jié)合單元，以便將Advice和Pointcut分開實現(xiàn)靈活配置。

AspectJ是基于注釋（Annotation）的，所以需要JDK5.0以上的支持。

AspectJ支持的注釋類型如下：

@Before

@After

@AfterReturning

@AfterThrowing

@Around

?

首先定義一個簡單的bean，CustomerBo實現(xiàn)了接口ICustomerBo

ICustomerBo.java如下：

package com.lei.demo.aop.aspectj;public interface ICustomerBo {void addCustomer();void deleteCustomer();String AddCustomerReturnValue();void addCustomerThrowException() throws Exception;void addCustomerAround(String name);}

?

?CustomerBo.java如下：

?

package com.lei.demo.aop.aspectj;public class CustomerBo implements ICustomerBo {public void addCustomer() {System.out.println("addCustomer() is running ...");}public void deleteCustomer() {System.out.println("deleteCustomer() is running ...");}public String AddCustomerReturnValue() {System.out.println("AddCustomerReturnValue() is running ...");return "abc";}public void addCustomerThrowException() throws Exception {System.out.println("addCustomerThrowException() is running ...");throw new Exception("Generic Error");}public void addCustomerAround(String name) {System.out.println("addCustomerAround() is running ,args:"+name);}}

?

一、????? 簡單的AspectJ，Advice和Pointcut結(jié)合在一起

首先沒有引入Pointcut之前，Advice和Pointcut是混在一起的

步驟，只需要兩步，如下：

創(chuàng)建一個Aspect類

配置Spring配置文件

?

第一步，創(chuàng)建Aspect類

LoggingAspect.java如下：

package com.lei.demo.aop.aspectj;import org.aspectj.lang.JoinPoint; import org.aspectj.lang.annotation.After; import org.aspectj.lang.annotation.Aspect; import org.aspectj.lang.annotation.Before;@Aspect public class LoggingAspect {@Before("execution(public * com.lei.demo.aop.aspectj.CustomerBo.addCustomer(..))")public void logBefore(JoinPoint joinPoint){System.out.println("logBefore() is running ...");System.out.println("hijacked:"+joinPoint.getSignature().getName());System.out.println("**********");}@After("execution(public * com.lei.demo.aop.aspectj.CustomerBo.deleteCustomer(..))")public void logAfter(JoinPoint joinPoint){System.out.println("logAfter() is running ...");System.out.println("hijacked:"+joinPoint.getSignature().getName());System.out.println("**********");} }

?

解釋：

1.??必須使用@Aspect在LoggingAspect聲明之前注釋，以便被框架掃描到

2.? 此例Advice和Pointcut結(jié)合在一起，類中的具體方法logBefore和logAfter即為Advice，是要注入的代碼，Advice方法上的表達式為Pointcut表達式，即定義了切入點，上例中@Before注釋的表達式代表執(zhí)行CustomerBo.addCustomer方法時注入logBefore代碼。

3.??在LoggingAspect方法上加入@Before或者@After等注釋

4.??"execution(public * com.lei.demo.aop.aspectj.CustomerBo.addCustomer(..))"是Aspect的切入點表達式，其中，*代表返回類型，后邊的就要定義要攔截的方法名，這里寫的的是com.lei.demo.aop.aspectj.CustomerBo.addCustomer表示攔截CustomerBo中的addCustomer方法，(..)代表參數(shù)匹配，此處表示匹配任意數(shù)量的參數(shù)，可以是0個也可以是多個，如果你確定這個方法不需要使用參數(shù)可以直接用()，還可以使用(*)來匹配一個任意類型的參數(shù)，還可以使用?(* , String)，這樣代表匹配兩個參數(shù)，第二個參數(shù)必須是String?類型的參數(shù)

5.??AspectJ表達式，可以對整個包定義，例如，execution(* com.lei.service..*.*(..))表示切入點是com.lei.sevice包中的任意一個類的任意方法，具體的表達式請自行百度。

?

第二步，配置Spring配置文件，

配置Spring-AOP-AspectJ.xml文件，如下：

<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/beanshttp://www.springframework.org/schema/beans/spring-beans-3.0.xsdhttp://www.springframework.org/schema/aophttp://www.springframework.org/schema/aop/spring-aop-3.0.xsd"><aop:aspectj-autoproxy/><bean id="customerBo" class="com.lei.demo.aop.aspectj.CustomerBo"/><bean id="logAspect" class="com.lei.demo.aop.aspectj.LoggingAspect" /></beans>

?

解釋：

1.??????<aop:aspectj-autoproxy/>啟動AspectJ支持，這樣Spring會自動尋找用@Aspect注釋過的類，其他的配置與spring普通bean配置一樣。

?

測試：

執(zhí)行App.java如下：

package com.lei.demo.aop.aspectj;import org.springframework.context.ApplicationContext; import org.springframework.context.support.ClassPathXmlApplicationContext;public class App {public static void main(String[] args) {ApplicationContext appContext = new ClassPathXmlApplicationContext(new String[] { "Spring-AOP-AspectJ.xml" });ICustomerBo customer=(ICustomerBo)appContext.getBean("customerBo");customer.addCustomer();System.out.println("-------------------------------------------");customer.deleteCustomer();} }

?

結(jié)果：

logBefore() is running ...

hijacked:addCustomer

**********

addCustomer() is running ...

-------------------------------------------

deleteCustomer() is running ...

logAfter() is running ...

hijacked:deleteCustomer

**********

?

二、????? 將Advice和Pointcut分開

需要三步，

創(chuàng)建Pointcut

創(chuàng)建Advice

配置Spring的配置文件

?

第一步，PointcutsDefinition.java定義了Pointcut，如下：

package com.lei.demo.aop.aspectj;import org.aspectj.lang.annotation.Aspect; import org.aspectj.lang.annotation.Pointcut;@Aspect public class PointcutsDefinition {@Pointcut("execution(* com.lei.demo.aop.aspectj.CustomerBo.*(..))")public void customerLog() {} }

?

解釋：

1. 類聲明前加入@Aspect注釋，以便被框架掃描到。

2. @Pointcut是切入點聲明，指定需要注入的代碼的位置，如上例中指定切入點為CustomerBo類中的所有方法，在實際業(yè)務中往往是指定切入點到一個邏輯層，例如?execution (* com.lei.business.service.*.*(..)），表示aop切入點為service包中所有類的所有方法，具體的表達式后邊會有介紹。

3. 方法customerLog是一個簽名，在Advice中可以用此簽名代替切入點表達式，所以不需要在方法體內(nèi)編寫實際代碼，只起到助記功能，例如此處代表操作CustomerBo類時需要的切入點。

?

第二步，創(chuàng)建Advice類

LoggingAspect.java如下：

package com.lei.demo.aop.aspectj;import org.aspectj.lang.JoinPoint; import org.aspectj.lang.annotation.After; import org.aspectj.lang.annotation.Aspect; import org.aspectj.lang.annotation.Before;@Aspect public class LoggingAspect {@Before("com.lei.demo.aop.aspectj.PointcutsDefinition.customerLog()")public void logBefore(JoinPoint joinPoint){System.out.println("logBefore() is running ...");System.out.println("hijacked:"+joinPoint.getSignature().getName());System.out.println("**********");}@After("com.lei.demo.aop.aspectj.PointcutsDefinition.customerLog()")public void logAfter(JoinPoint joinPoint){System.out.println("logAfter() is running ...");System.out.println("hijacked:"+joinPoint.getSignature().getName());System.out.println("**********");} }

?

注釋：

1.???????@Before和@After使用PointcutsDefinition中的方法簽名代替Pointcut表達式找到相應的切入點，即通過簽名找到PointcutsDefinition中customerLog簽名上的Pointcut表達式，表達式指定切入點為CustomerBo類中的所有方法。所以此例中Advice類LoggingAdvice，為CustomerBo中的所有方法都加入了@Before和@After兩種類型的兩種操作。

2.???????對于PointcutsDefinition來說，主要職責是定義Pointcut，可以在其中第一多個切入點，并且可以用便于記憶的方法簽名進行定義。

3.???????單獨定義Pointcut的好處是，一是通過使用有意義的方法名，而不是難讀的Pointcut表達式，使代碼更加直觀；二是Pointcut可以實現(xiàn)共享，被多個Advice直接調(diào)用。若有多個Advice調(diào)用某個Pointcut，而這個Pointcut的表達式在將來有改變時，只需修改一個地方，維護更加方便。

?

第三步，配置Spring配置文件，配置文件并沒有改變

配置Spring-AOP-AspectJ.xml文件，如下：

<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/beanshttp://www.springframework.org/schema/beans/spring-beans-3.0.xsdhttp://www.springframework.org/schema/aophttp://www.springframework.org/schema/aop/spring-aop-3.0.xsd"><aop:aspectj-autoproxy/><bean id="customerBo" class="com.lei.demo.aop.aspectj.CustomerBo"/><bean id="logAspect" class="com.lei.demo.aop.aspectj.LoggingAspect" /></beans>

?

App.java不變，運行測試代碼App.java

輸出結(jié)果：

logBefore() is running ...

hijacked:addCustomer

**********

addCustomer() is running ...

logAfter() is running ...

hijacked:addCustomer

**********

-------------------------------------------

logBefore() is running ...

hijacked:deleteCustomer

**********

deleteCustomer() is running ...

logAfter() is running ...

hijacked:deleteCustomer

**********

?

三、???? 切入點表達式

Spring3.0.5幫助文檔中的切入點表達式如下：

?

Some examples of common pointcut expressions are given below.

?

the execution of any public method:

execution(public * *(..))

the execution of any method with a name beginning with "set":

execution(* set*(..))

the execution of any method defined by the AccountService interface:

execution(* com.xyz.service.AccountService.*(..))

the execution of any method defined in the service package:

execution(* com.xyz.service.*.*(..))

the execution of any method defined in the service package or a sub-package:

execution(* com.xyz.service..*.*(..))

any join point (method execution only in Spring AOP) within the service package:

within(com.xyz.service.*)

any join point (method execution only in Spring AOP) within the service package or a sub-package:

within(com.xyz.service..*)

any join point (method execution only in Spring AOP) where the proxy implements the AccountService interface:

this(com.xyz.service.AccountService)

'this' is more commonly used in a binding form :- see the following section on advice for how to make the proxy object available in the advice body.

?

any join point (method execution only in Spring AOP) where the target object implements the AccountService interface:

target(com.xyz.service.AccountService)

'target' is more commonly used in a binding form :- see the following section on advice for how to make the target object available in the advice body.

?

any join point (method execution only in Spring AOP) which takes a single parameter, and where the argument passed at runtime is Serializable:

args(java.io.Serializable)
'args' is more commonly used in a binding form :- see the following section on advice for how to make the method arguments available in the advice body.

Note that the pointcut given in this example is different to execution(* *(java.io.Serializable)): the args version matches if the argument passed at runtime is Serializable, the execution version matches if the method signature declares a single parameter of type Serializable.

?

any join point (method execution only in Spring AOP) where the target object has an @Transactional annotation:

@target(org.springframework.transaction.annotation.Transactional)

'@target' can also be used in a binding form :- see the following section on advice for how to make the annotation object available in the advice body.

?

any join point (method execution only in Spring AOP) where the declared type of the target object has an @Transactional annotation:

@within(org.springframework.transaction.annotation.Transactional)

'@within' can also be used in a binding form :- see the following section on advice for how to make the annotation object available in the advice body.

?

any join point (method execution only in Spring AOP) where the executing method has an @Transactional annotation:

@annotation(org.springframework.transaction.annotation.Transactional)

'@annotation' can also be used in a binding form :- see the following section on advice for how to make the annotation object available in the advice body.

?

any join point (method execution only in Spring AOP) which takes a single parameter, and where the runtime type of the argument passed has the@Classified annotation:

@args(com.xyz.security.Classified)

'@args' can also be used in a binding form :- see the following section on advice for how to make the annotation object(s) available in the advice body.

?

any join point (method execution only in Spring AOP) on a Spring bean named 'tradeService':

bean(tradeService)

any join point (method execution only in Spring AOP) on Spring beans having names that match the wildcard expression '*Service':

bean(*Service)

轉(zhuǎn)載于:https://www.cnblogs.com/jcomet/p/5570460.html

總結(jié)

以上是生活随笔為你收集整理的Spring3系列12-Spring AOP AspectJ的全部內(nèi)容，希望文章能夠幫你解決所遇到的問題。

如果覺得生活随笔網(wǎng)站內(nèi)容還不錯，歡迎將生活随笔推薦給好友。