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:
1
2
3
|
< 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:
1
2
3
4
5
6
7
8
9
10
11
|
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:
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
|
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:
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
|
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:
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
|
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:
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
|
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
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
|
<%@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
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
|
<%@ 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:
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
|
<%@ 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服务器之家。
原文链接:http://blog.csdn.net/weixin_36380516/article/details/70144559