servlet监听实现统计在线人数功能附源码下载

2019-11-26 12:36:10

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本文实例为大家分享了servlet统计在线人数的具体代码，供大家参考，具体内容如下

ServletContext事件监听器---->针对applicationScope
ServletContextListener(*)
对整个Web应用的装载和卸载进行监听。
ServletContextAttributeListener
对ServletContext中的信息存放、删除和替换进行监听。
ServletContext就是Servlet上下文监听，在web中表示的是对启动服务和销毁服务进行监听，需要实现的接口：
ServletContextListener接口，实现的就是对上下午进行监听：
void contextInitialized(ServletContextEvent sce)：启动上下文时的监听
void contextDestroyed(ServletContextEvent sce)：销毁上下文时进行的监听
除了对上下文的启动和销毁进行监听的之外，还可以对上下文的属性进行监听：ServletContextAttributeListener接口。
void attributeAdded(ServletContextAttributeEvent event)：设置上下文属性监听
void attributeRemoved(ServletContextAttributeEvent event)：移除上下文属性的监听
void attributeReplaced(ServletContextAttributeEvent event)：修改上下文属性的监听
ServletContextAttributeEvent：事件，可以通过事件取得属性的内容和名称。
・取得属性名称：public java.lang.String getName()
・取得属性的值：public java.lang.Object getValue()
效果如下图：

当登录一个账号时

打开另一个浏览器，再登录一个账号

如上图，我们可以看到，程序已经完成了统计在线人数和显示人员列表的功能，那么他的实现流程是什么呢？

我们可以通过ServletContextListener完成在线人数的统计和显示在线人数列表，首先listener和filter一样要在web.xml中进行描述。

代码如下：

<listener>  <listener-class>net.jvsun.ListenerTest</listener-class> </listener>

为了测试这个程序，我们也必须完成用户登录功能。
数据库连接帮助类：

public class JDBCHelper {  public static final String DRIVER = "oracle.jdbc.driver.OracleDriver";  public static final String URL = "jdbc:oracle:thin:@localhost:1521:xxx";  public static final String DBNAME = "scott";  public static final String PASSWORD = "xxx";  public static Connection getConn() throws Exception{  Class.forName(DRIVER);  Connection conn = DriverManager.getConnection(URL, DBNAME, PASSWORD);  return conn;  } }

用户实体类：

public class UserPOJO implements Serializable{  private static final long serialVersionUID = 7554548269035753256L;  private int id;  private String username;  private String password;  public int getId() {  return id;  }  public void setId(int id) {  this.id = id;  }  public String getUsername() {  return username;  }  public void setUsername(String username) {  this.username = username;  }  public String getPassword() {  return password;  }  public void setPassword(String password) {  this.password = password;  }  public UserPOJO(int id, String username, String password) {  super();  this.id = id;  this.username = username;  this.password = password;  }  public UserPOJO(String username, String password) {  this.username = username;  this.password = password;  }  public UserPOJO() {  super();  // TODO Auto-generated constructor stub  }  }

数据库处理类：

public class UserDAO {  public UserPOJO login(String username, String password) {  UserPOJO user=null;  Connection conn = null;  PreparedStatement pstate = null;  ResultSet res = null;  try {  conn=JDBCHelper.getConn();  String sql="select id,username from userinfo where username=? and password=?";  pstate = conn.prepareStatement(sql);  pstate.setString(1, username);  pstate.setString(2, password);  res = pstate.executeQuery();  while(res.next()){  user=new UserPOJO(res.getInt(1),username,null);  }  } catch (Exception e) {  e.printStackTrace();  }finally{  try {  res.close();  pstate.close();  conn.close();  } catch (SQLException e) {  e.printStackTrace();  }   }  return user;  } }

servlet类：

public class UserServlet extends HttpServlet{   @Override  protected void doGet(HttpServletRequest request, HttpServletResponse response)  throws ServletException, IOException {  String path = request.getContextPath();  response.setContentType("text/html; charset=utf-8");  request.setCharacterEncoding("utf-8");  String username = request.getParameter("username");  String password = request.getParameter("password");  ServletContext application = this.getServletContext();//取得application对象  List<String> list = (List<String>) application.getAttribute("allUser");  if(list.indexOf(username) == -1){  UserPOJO pojo = new UserDAO().login(username, password);  if(null != pojo){  HttpSession session = request.getSession(true);//取得session对象  session.setAttribute("userName", username);  }   }  response.sendRedirect(path+"/index.jsp");  }   @Override  protected void doPost(HttpServletRequest req, HttpServletResponse resp)  throws ServletException, IOException {  doGet(req, resp);  }  }

监听类：

public class ListenerTest implements ServletContextListener,HttpSessionAttributeListener,HttpSessionListener{  ServletContext application = null;  public void contextDestroyed(ServletContextEvent event) {  System.out.println("服务器关闭");  }   public void contextInitialized(ServletContextEvent event) {  List<String> list = new ArrayList<String>();  //用来保存所有已登录的用户  application = event.getServletContext();  //取得application对象  application.setAttribute("allUser", list);  //将集合设置到application范围属性中去   }   public void attributeAdded(HttpSessionBindingEvent se) {  List<String> list = (List<String>)application.getAttribute("allUser");  //假设：用户登陆成功之后，只将户名设置到session中  String userName = (String)se.getValue();  //取得用户名  if(list.indexOf(userName) == -1){  //表示此用户之前没有登陆  list.add(userName);  application.setAttribute("allUser", list);  }  }   public void attributeRemoved(HttpSessionBindingEvent se) {  List<String> list = (List<String>)application.getAttribute("allUser");  list.remove((String)se.getValue());  application.setAttribute("allUser", list);  }   public void attributeReplaced(HttpSessionBindingEvent se) {   }   public void sessionCreated(HttpSessionEvent event) {   }   public void sessionDestroyed(HttpSessionEvent event) {   } }

登录页面

<%@page contentType="text/html; charset=utf-8"%> <%@page import="java.util.*" %> <%  String path = request.getContextPath();  %>  <html>  <body>   <form action="<%=path %>/Login" method="post">  账号：  <input type="text" name="username" />  <br />  密码：  <input type="password" name="password" />  <br />  <input type="submit" value="提交" />  </form>   </body>  </html>

显示在线人数和在线人员的列表界面

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%> <% String path = request.getContextPath(); String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/"; %>  <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"> <html>  <head>  <base href="<%=basePath%>" rel="external nofollow" rel="external nofollow" >  <title></title>  </head>   <body>  <ul>  <%  System.out.println(application.getAttribute("allUser"));  if(null != application.getAttribute("allUser")){  List<String> list = (List<String>)application.getAttribute("allUser");  %>  <h2>在线人数:<%=list.size() %></h2>  <%  for(String s:list){  %>  <a>姓名：</a><%=s %><a>---->此时在线</a><br>   <%  }  }  %>  </ul>  <hr/>  <a href="<%=path %>/logout.jsp" rel="external nofollow" >注销</a>  </body> </html>

注销界面：

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%> <% String path = request.getContextPath(); String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/"; %>  <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"> <html>  <head>  <base href="<%=basePath%>" rel="external nofollow" rel="external nofollow" >  <title>logout</title>  </head>  <body>  <%  session.removeAttribute("username");  session.invalidate();  response.sendRedirect("login.jsp");  %>  </body> </html>

代码下载地址：servlet统计在线人数

以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持武林网。

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