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日志总数:1304
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建立时间:2006年5月29日




[Spring]spring 2.0 aop编程
软件技术

lhwork 发表于 2006/10/10 10:05:08

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adviceBefore 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();   }   }前面这是讲了许多的概念,下面以一个例子来说明:一个很好理解的aop 例子,也就是日志服务。先从aop第一种方式来实现,也就是xml配置方式先创建基本的日志类:public class Logger {     private static Log log = LogFactory.getLog(Logger.class);     public void entry(String message) {        log.info(message);    }}这里只是简单的一个方法,当然实际情况可能不同。由于xml配置需要一个方面的实现bean所以创建一个简单的bean :public class LogBean {     private Logger logger = new Logger();     public Object aroundLogCalls(ProceedingJoinPoint joinPoint) throws Throwable {        logger.entry("before invoke method:"                     + joinPoint.getSignature().getName());        Object object = joinPoint.proceed();        logger.entry("after invoke method:"                     + joinPoint.getSignature().getName());        return object;    }}这里采取简单的around advice,其他类型的advice 基本上都差不多当然有了这两个核心的日志类,需要一个测试类,用于测试。public class TestBean {     public void method1() {        System.out.println("in method1");    }     public void method2() {        System.out.println("in method2");    }}这就是需要测试的类了,需要记录日志的方法只有两个,这里用System.out.println,只是想显示方法的调用顺序。然后关键的在于xml的配置了<?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" xsi:schemaLocation="http://www.springframework.org/schema/beanshttp://www.springframework.org/schema/beans/spring-beans.xsdhttp://www.springframework.org/schema/aophttp://www.springframework.org/schema/aop/spring-aop.xsd">  <aop:config>    <!--  expression 表示要执行的匹配表达式,这里匹配所有的public方法,但是去除logger类的所有方法,防止无限调用-->      <aop:pointcut id="loggableCalls"          expression="execution(public * *(..)) and !execution(* org.spring.test.aop.log.Logger.*(..))"/>  <aop:aspect id="logAspect" ref="logBean">   <aop:around pointcut-ref="loggableCalls" method="aroundLogCalls"/>  </aop:aspect>  </aop:config> <bean id="logBean" class="org.spring.test.aop.log.LogBean" /> <bean id="testBean" class="org.spring.test.aop.log.TestBean"/> </beans>现在写一个测试类:public class LogXmlTest extends RootTest {     @Override    protected String getBeanXml() {        return "org/spring/test/aop/log/bean.xml";    }     public void testLog() {        TestBean bean = (TestBean) ctx.getBean("testBean");        bean.method1();        bean.method2();    } }public abstract class RootTest extends TestCase {     protected ApplicationContext  ctx;     protected Log log = LogFactory.getLog(getClass());     protected RootTest() {        ctx = new ClassPathXmlApplicationContext(getBeanXml());    }     protected abstract String getBeanXml(); }打印的消息如下:2006-09-17 11:08:28,203 INFO [org.spring.test.aop.log.Logger] - before invoke method:method1in method12006-09-17 11:08:28,203 INFO [org.spring.test.aop.log.Logger] - after invoke method:method12006-09-17 11:08:28,218 INFO [org.spring.test.aop.log.Logger] - before invoke method:method2in method22006-09-17 11:08:28,218 INFO [org.spring.test.aop.log.Logger] - after invoke method:method2第二种实现方式,采用注释方式:Logger 类不变创建一个LogAspect类@Aspectpublic class LogAspect {     private Logger logger = new Logger();     @Pointcut("execution(public * *(..))")    public void publicMethods() {     }     @Pointcut("execution(* org.spring.test.aop.log.Logger.*(..))")    public void logObjectCalls() {     }     @Pointcut("publicMethods()&&!logObjectCalls()")    public void loggableCalls() {     }     @Around("loggableCalls()")    public Object aroundLogCalls(ProceedingJoinPoint joinPoint) throws Throwable {        logger.entry("before invoke method:"                     + joinPoint.getSignature().getName());        Object object = joinPoint.proceed();        logger.entry("after invoke method:"                     + joinPoint.getSignature().getName());        return object;    }}配置文件就简单多了<?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" xsi:schemaLocation="http://www.springframework.org/schema/beanshttp://www.springframework.org/schema/beans/spring-beans.xsdhttp://www.springframework.org/schema/aophttp://www.springframework.org/schema/aop/spring-aop.xsd">  <aop:aspectj-autoproxy/>  <!-- 或者使用以下定义    <bean class="org.springframework.aop.aspectj.annotation.AnnotationAwareAspectJAutoProxyCreator" />  --> <bean id="logAspect" class="org.spring.test.aop.log.LogAspect"/> <bean id="testBean" class="org.spring.test.aop.log.TestBean"/> </beans>测试类:跟上面的差不多把xml文件换掉就行打印的方式差不多个人还是比较喜欢第二种实现。 


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