這篇文章旨在記錄關(guān)于SpringMVC過程中會用到的監(jiān)聽器

1.Servlet監(jiān)聽

用來監(jiān)聽Servlet的生命周期。
主要類：ServletContextListener（監(jiān)聽網(wǎng)站啟動過程）,
HttpSessionListener（監(jiān)聽客戶端會話過程）, HttpSessionAttributeListener
實現(xiàn)：
創(chuàng)建類實現(xiàn)以上的接口比如：

public class TestListener implements ServletContextListener,
        HttpSessionListener, HttpSessionAttributeListener {
    .....
｝

web.xml配置：

<listener>
        <listener-class>com.test.TestListener</listener-class>
</listener>

2.Bean 初始化監(jiān)聽

可以監(jiān)聽Spring創(chuàng)建Bean的實例的初始化前后
主要類：
BeanPostProcessor
實現(xiàn)：

public class TestProcess implements BeanPostProcessor,Ordered {
    public Object postProcessBeforeInitialization(Object o, String s) throws BeansException {
        System.out.println("postProcessBeforeInitialization");
        return o;
    }

    public Object postProcessAfterInitialization(Object o, String s) throws BeansException {
        System.out.println("postProcessAfterInitialization");
        return o;
    }


    public int getOrder() {
        return 1;
    }
}

Order主要在于多個同等類時執(zhí)行的順序，return返回的是對象，這里可以偷天換日。

SpringContext.xml：

<bean id="testpost" class="....TestProcess"></bean>

3.類的初始化和銷毀的監(jiān)聽。

此監(jiān)聽旨在監(jiān)聽bean的自身初始化和銷毀過程，初始化的執(zhí)行方法在第2個監(jiān)聽之后
實現(xiàn)：
第一種1.SpringContext.xml

<bean id="helloWorld" class="com.tutorialspoint.HelloWorld"
init-method="init" destroy-method="destroy">
<property name="message" value="Hello World!"/>
</bean>

通過init-method和destroy-method設(shè)置。
第二種2.在bean中

@PostConstruct
public void init(){
System.out.println("Bean is going through init.");
}
@PreDestroy
public void destroy(){
System.out.println("Bean will destroy now.");
}

4.AOP。

面向切面編程
第一種方式：
SpringContext.xml:

<aop:config>
        <aop:aspect id="myaspect" ref="peoAsp">
            <aop:pointcut  id="mypointcut" expression="execution(* jis.*.*(..))"/>
            <aop:before method="beforeAdvice" pointcut-ref="mypointcut"/>
            <aop:after-throwing method="AfterThrowingAdvice" pointcut-ref="mypointcut" throwing="ex"/>
            <aop:after-returning method="afterReturningAdvice" pointcut-ref="mypointcut" returning="retVal"/>
        </aop:aspect>
    </aop:config>

第二種方式：
Bean中：

@Aspect
public class PeoAsp  {

    public PeoAsp(){}

    @Pointcut("execution(* com.jis.People.aspTest(..))")
    public void selectAll(){};

    /**
     * This is the method which I would like to execute
     * before a selected method execution.
     */
    @Before("selectAll()")
    public void beforeAdvice(){
        System.out.println("Going to setup student profile.");
    }
    /**
     * This is the method which I would like to execute
     * after a selected method execution.
     */
    @After("selectAll()")
    public void afterAdvice(){
        System.out.println("Student profile has been setup.");
    }
    /**
     * This is the method which I would like to execute
     * when any method returns.
     */
    @AfterReturning(pointcut = "selectAll()",returning = "retVal")
    public void afterReturningAdvice(Object retVal){
        System.out.println("Returning:" + retVal.toString() );
    }
    /**
     * This is the method which I would like to execute
     * if there is an exception raised.
     */
    public void AfterThrowingAdvice(Exception ex){
        System.out.println("There has been an exception: " + ex.toString());
    }


}

并在SpringContext中配置：
<aop:aspectj-autoproxy/>
<bean class="com.jis.PeoAsp" id="peoAsp"></bean>