spring aop 2.0 编程

在spring2.0中，aop发生了很大的变化：
主要分为两大方面
1.支持简单的aop xml配置
2.支持@AspectJ的注释

先来看一看第一种情况：
申明一个aspect，在xml中的申明如下：

<aop:config>

  <aop:aspect id="myAspect" ref="aBean">

    ...

  </aop:aspect>

</aop:config>

<bean id="aBean" class="...">

  ...

</bean>

申明pointcut

<aop:config>

  <aop:pointcut id="businessService"

        expression="execution(* com.xyz.myapp.service.*.*(..))"/>

</aop:config>

申明advice

Before advice：

<aop:aspect id="beforeExample" ref="aBean">

    <aop:before

      pointcut-ref="dataAccessOperation"

      method="doAccessCheck"/>

</aop:aspect>

After returning advice:

<aop:aspect id="afterReturningExample" ref="aBean">

 

    <aop:after-returning

      pointcut-ref="dataAccessOperation"

      method="doAccessCheck"/>

         

    ...

   

</aop:aspect>

或者带有返回参数
<aop:aspect id="afterReturningExample" ref="aBean">

 

    <aop:after-returning

      pointcut-ref="dataAccessOperation"

      returning="retVal"

      method="doAccessCheck"/>

         

    ...

   

</aop:aspect>

 

After throwing advice：

<aop:aspect id="afterThrowingExample" ref="aBean">

 

    <aop:after-throwing

      pointcut-ref="dataAccessOperation"

      method="doRecoveryActions"/>

         

    ...

   

</aop:aspect>

或者带有throwing

<aop:aspect id="afterThrowingExample" ref="aBean">

 

    <aop:after-throwing

      pointcut-ref="dataAccessOperation"

      throwing="dataAccessEx"

      method="doRecoveryActions"/>

         

    ...

   

</aop:aspect>

After (finally) advice：

<aop:aspect id="afterFinallyExample" ref="aBean">

 

    <aop:after

      pointcut-ref="dataAccessOperation"

      method="doReleaseLock"/>

         

    ...

   

</aop:aspect>

Around advice：

<aop:aspect id="aroundExample" ref="aBean">

 

    <aop:around

      pointcut-ref="businessService"

      method="doBasicProfiling"/>

         

    ...

   

</aop:aspect>

Advice parameters：

<aop:before

  pointcut="Pointcuts.anyPublicMethod() and @annotation(auditable)"

  method="audit"

  arg-names="auditable"/>

对于引入接口（Introductions）：

<aop:aspect id="usageTrackerAspect" ref="usageTracking">

  <aop:declare-parents

      types-matching="com.xzy.myapp.service.*+",

      implement-interface="UsageTracked"
      default-impl=" service.tracking.DefaultUsageTracked"/>

  <aop:before

    pointcut="com.xyz.myapp.SystemArchitecture.businessService()

              and this(usageTracked)"

    method="recordUsage"/>

</aop:aspect>

前面主要介绍了如何通过xml实现aop编程，下面主要介绍如何通过@AspectJ来实现。
为了使@AspectJ 支持生效,
需要做以下步骤：
在xml中设置

<aop:aspectj-autoproxy/>

或者
在xml中加入
<bean class="org.springframework.aop.aspectj.annotation.AnnotationAwareAspectJAutoProxyCreator" />

声明 aspect

<bean id="myAspect" class="org.xyz.NotVeryUsefulAspect">
   <!-- configure properties of aspect here as normal -->
</bean>
 

package org.xyz;
import org.aspectj.lang.annotation.Aspect;
 

@Aspect

public class NotVeryUsefulAspect {
 

}

声明 pointcut


@Pointcut("execution(* transfer(..))")
public void transfer() {}

声明 advice

Before advice:

@Before("com.xyz.myapp.SystemArchitecture.dataAccessOperation()")

  public void doAccessCheck() {

    // ...

  }

After returning advice:

@AfterReturning("com.xyz.myapp.SystemArchitecture.dataAccessOperation()")

  public void doAccessCheck() {

    // ...

  }

或者
@AfterReturning(
pointcut="com.xyz.myapp.SystemArchitecture.dataAccessOperation()",
returning="retVal")

public void doAccessCheck(Object retVal) {

    // ...

  }

After throwing advice：

@AfterThrowing("SystemArchitecture.dataAccessOperation()")

  public void doRecoveryActions() {

    // ...

  }

或者
@AfterThrowing(

    pointcut=" SystemArchitecture.dataAccessOperation()",

    throwing="ex")

  public void doRecoveryActions(DataAccessException ex) {

    // ...

  }

After (finally) advice：

@After("com.xyz.myapp.SystemArchitecture.dataAccessOperation()")

  public void doReleaseLock() {

    // ...

  }

Around advice：

@Around("com.xyz.myapp.SystemArchitecture.businessService()")

  public Object doBasicProfiling( ProceedingJoinPoint pjp) throws Throwable {

    // start stopwatch

    Object retVal = pjp.proceed();

    // stop stopwatch

    return retVal;

  }

Advice parameters：

@Before("com.xyz.myapp.SystemArchitecture.dataAccessOperation() &&" + "args(account,..)" )

public void validateAccount(Account account) {

  // ...

}

声明参数名称：

@Before(

   value="com.xyz.lib.Pointcuts.anyPublicMethod() && " +

         "@annotation(auditable)",

   argNames="auditable" )

public void audit(Auditable auditable) {

  AuditCode code = auditable.value();

  // ...

} 

Advice 排序：

一般以声明的方法次序为先后

不同的 Advice ，通过实现 Ordered 接口，来排序

Introductions

用于引入新的接口
@Aspect

public class UsageTracking {

 

  @DeclareParents(value="com.xzy.myapp.service.*+",

                  defaultImpl=DefaultUsageTracked.class)

  public static UsageTracked mixin;

 

  @Before("com.xyz.myapp.SystemArchitecture.businessService() &&" +

          "this(usageTracked)")

  public void recordUsage(UsageTracked usageTracked) {

    usageTracked.incrementUseCount();

  }

 

}