Servlet 监听器----ServletRequest

ServletRuquest监听器

在ServletRequest级别上有3个监听器接口：    ServletRequestListener    ServletRequestAttributeListener    AsyncListener

1. ServletRequestListener

ServletRequestListener对Servlet的创建和销毁做出响应。在Servlet中的通过池来重启ServletRequest的，创建ServletRequest的时间花费相当于从池中获取它的时间，销毁时间则相当于它返回到池的时间。

ServletRequestListener接口定义两个方法创建ServletRequest是调用:    void requestInitialized(ServletRequestEvent event)销毁ServletRequest是调用:    void requestDestroyed(ServletRequestEvent event)

例子：

public class ServletRequestTest implements ServletRequestListener{    @Override    public void requestDestroyed(ServletRequestEvent sre) {        // TODO Auto-generated method stub        ServletRequest servletRequest = sre.getServletRequest();        Long  start = (Long) servletRequest.getAttribute("start");        Long end = System.nanoTime();        HttpServletRequest httpServletRequest = (HttpServletRequest) servletRequest;        StringBuffer uri = httpServletRequest.getRequestURL();        System.out.println("time taken to execute" + uri+":"+((end-start)/1000)+"microseconds");    }    @Override    public void requestInitialized(ServletRequestEvent sre) {        // TODO Auto-generated method stub        ServletRequest servletRequest =  sre.getServletRequest();        servletRequest.setAttribute("start", System.nanoTime());    }}

注册

    <listener>        <listener-class>listener.ServletRequestTest</listener-class>    </listener>

结果：

2. ServletRequestAttributeListener

每当HttpRequest中添加，删除或替换了某个属性时，ServletRequestAttributeListener的实现都会收到通知，
该监听器接口种有三个方法:
void attributeAdded(HttpRequestBindingEvent event)
void attributeRemoveed(HttpRequestBindingEvent event)
void attributeReplaced(HttpRequestBindingEvent event)
获取属性名和属性值,使用以下两个方法
java.lang.String getName()
java.lang.Object getValue()