spring aop 2.0 编程(三)

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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。