Question

我开发了一个servlet，用户在其中输入名称，点击提交按钮后，它会向用户表示问候，我还想添加它应该显示当前登录用户数的功能，例如，如果我点击一个浏览器的servlet应该显示登录的用户数是1，因为我是第一个用户，如果有其他人从下一个浏览器点击servlet，它应该显示他是2个访问者，所以这样它会显示他当前登录的用户数量，请告知如何实现这一目标..

项目的web.xml是..

   <?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xmlns:web="http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd" id="WebApp_ID" version="3.0">
  <display-name>FirstDemo</display-name>


  <servlet>
<servlet-name>hello</servlet-name>
<servlet-class>com.saral.MyServlet</servlet-class>
</servlet>


<servlet-mapping>
<servlet-name>hello</servlet-name>
<url-pattern>/helloServlet</url-pattern>
</servlet-mapping>
<welcome-file-list>

<welcome-file>home.html</welcome-file>
</welcome-file-list> 

</web-app>

HTML是......

<html>
<head>
<title> A Simple web Application</title>
</head>
<body>
<form method="get" action="helloServlet">
Name<input type="text" name="txtName">
<br><input type="submit" value="Login">
</form>
</body>
</html>

请告知如何添加登录用户数的功能。下面是我的项目结构的快照是.. enter link description here

我已在下面添加了计数器类......

package com.saral;

import javax.servlet.ServletContext;
import javax.servlet.http.HttpSessionEvent;
import javax.servlet.http.HttpSessionListener;


public class SessionCounter implements HttpSessionListener
{
        private static int count;

        public SessionCounter()
        {
        }

        public void sessionCreated(HttpSessionEvent arg0)
        {
                count++;
                ServletContext sContext = arg0.getSession().getServletContext();
                synchronized (sContext)
                {
                        sContext.setAttribute("sessionCount", new Integer(count));
                }
        }

        public void sessionDestroyed(HttpSessionEvent arg0)
        {
                count--;
                ServletContext sContext = arg0.getSession().getServletContext();
                synchronized (sContext)
                {
                        sContext.setAttribute("sessionCount", new Integer(count));
                }
        }
}

我已经修改了我的servlet ..

import java.io.IOException;
import java.io.PrintWriter;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
 * Servlet implementation class First
 */
//@WebServlet("/First")
public class MyServlet extends HttpServlet
{
    private static final long serialVersionUID = 1L;


    /**
     * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
     */
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // TODO Auto-generated method stub
        String name=request.getParameter("txtName");
        response.setContentType("text/html");
        request.getAttribute("sessionCount");
        PrintWriter out=response.getWriter();
        out.println("Hello,"+name);
        out.println("<br> this output is generated by a simple servlet.");
        out.println("--->"+(request.getAttribute("sessionCount")));
        out.close();


    }

}

但是我得到的会话是空的......在输出中... http://imageshack.us/photo/my-images/405/sessionoutput.jpg/ output of session

请告知我如何获得价值我现在得到无效礼仪，我想要我首先请求它显示1如果我打开第二它应该显示2，请告知如何实现这一点，因为我卡住了在此。

Answer 1

您可以在应用程序范围内存储一个简单的POJO，以便维护计数。

将功能添加到servlet

1 个答案: