一、HttpServletRequest對象的生命周期監(jiān)聽器

????????ServletRequestListener接口定義了ServletRequest(是HttpServletRequest接口的父接口類型)對象生命周期的監(jiān)聽行為。

void requestInitialized(ServletRequestEvent sre)

??????? HttpServletRequest對象創(chuàng)建后會(huì)觸發(fā)該監(jiān)聽器方法，并將已創(chuàng)建HttpServletRequest對象傳遞到該方法中

void requestDestoryed(HttpSessionEvent sre)

??????? HttpServletRequest對象在銷毀之前會(huì)觸發(fā)該監(jiān)聽方法，并將要銷毀的HttpServletRequest對象傳遞到該方法中

二、創(chuàng)建能夠監(jiān)聽 HttpServletRequest生命周期的監(jiān)聽器?

實(shí)現(xiàn):

package cn.itcast.listener;

import javax.servlet.ServletRequestEvent;
import javax.servlet.ServletRequestListener;
import javax.servlet.http.HttpServletRequest;

public class HttpServletRequestLifecycleListener implements ServletRequestListener {
    @Override
    public void requestDestroyed(ServletRequestEvent sre) {
        System.out.println("-------------Start requestDestroyed---------------");
        System.out.println((HttpServletRequest)sre.getServletRequest());
        System.out.println("-------------End requestDestroyed---------------");
    }

    @Override
    public void requestInitialized(ServletRequestEvent sre) {
        System.out.println("-------------Start requestInitialized---------------");
        System.out.println((HttpServletRequest)sre.getServletRequest());
        System.out.println("-------------End requestInitialized---------------");
    }
}

三、創(chuàng)建能夠監(jiān)聽 HttpServletRequest對象的屬性操作監(jiān)聽器?

ServletRequestAttributeListener接口定義了對于HttpServletRequest對象屬性操作的監(jiān)聽行為。

void attributeAdded(ServletRequestAttributeEvent srae)

????????向HttpServletRequest對象中添加屬性是會(huì)觸發(fā)該監(jiān)聽方法，并將HttpServletRequest對象傳遞到該方法中，觸發(fā)事件的方法HttpServletRequest.setAttribute("key","value")

void attributeRemove(ServletRequestAttributeEvent srae)

????????HttpServletRequest對象中添加屬性是會(huì)觸發(fā)該監(jiān)聽方法，并將HttpServletRequest對象傳遞到該方法中，觸發(fā)事件的方法HttpServletRequest.removeAttribute("key","value")

void attributeReplaced(ServletRequestAttributeEvent srae)

????????HttpServletRequest對象中添加屬性是會(huì)觸發(fā)該監(jiān)聽方法，并將HttpServletRequest對象傳遞到該方法中，觸發(fā)事件的方法HttpServletRequest.setAttribute("key","value")

?實(shí)例代碼:

servlet:

package cn.itcast.listener;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
@WebServlet("/requestAttr.do")
public class HttpServletRequestAttrServlet extends HttpServlet {

    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        req.setAttribute("key","test");
        req.setAttribute("key","test2");
        req.removeAttribute("key");
    }
}

監(jiān)聽:

package cn.itcast.listener;

import javax.servlet.ServletRequestAttributeEvent;
import javax.servlet.ServletRequestAttributeListener;

public class HttpServletRequestAttrListener implements ServletRequestAttributeListener {
    @Override
    public void attributeRemoved(ServletRequestAttributeEvent srae) {
        System.out.println("-------HttpServletRequestAttrListener---Start attributeRemoved----------");
        System.out.println("Name:"+srae.getName()+" Value:"+srae.getValue());
        System.out.println("-------HttpServletRequestAttrListener---End attributeRemoved----------");
    }

    @Override
    public void attributeReplaced(ServletRequestAttributeEvent srae) {
        System.out.println("-------HttpServletRequestAttrListener---Start attributeReplaced----------");
        System.out.println("Name:"+srae.getName()+" Value:"+srae.getValue());
        System.out.println("-------HttpServletRequestAttrListener---End attributeReplaced----------");
    }

    @Override
    public void attributeAdded(ServletRequestAttributeEvent srae) {
        System.out.println("-------HttpServletRequestAttrListener---Start attributeAdded----------");
        System.out.println("Name:"+srae.getName()+" Value:"+srae.getValue());
        System.out.println("-------HttpServletRequestAttrListener---End attributeAdded----------");
    }
}

輸出:

-------HttpServletRequestAttrListener---Start attributeAdded----------

Name:key Value: test

-------HttpServletRequestAttrListener---End attributeAdded----------

HttpServletRequestAttrListener---Start attributeReplaced----------

Name:key Value: test

-------HttpServletRequestAttrListener---End attributeReplaced----------

HttpServletRequestAttrListener---Start attributeRemoved----------

Name:key Value: test2

-------HttpServletRequestAttrListener---End attributeRemoved----------文章來源地址http://www.zghlxwxcb.cn/news/detail-816568.html

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