首先我們需要先建立一個Bean: User
package cn.class3g.web.domain;
public class User {
private String username;
private String password;
public User() {
super();
// TODO Auto-generated constructor stub
}
public User(String username, String password) {
super();
this.username = username;
this.password = password;
}
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;
}
}
然後我們建立用戶登錄界面login.jsp
<form action="${pageContext.request.contextPath }/servlet/LoginServlet" method="post">
用戶名：<input type="text" name="username"><br>
密碼：<input type="password" name="password"><br>
<input type="submit" value="登錄">
</form>
建立登錄用戶的Servlst LoginServlet
package cn.class3g.web.servlet;
import java.io.IOException;
import java.io.PrintWriter;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import cn.class3g.web.domain.User;
public class LoginServlet extends HttpServlet {
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
this.doPost(request, response);
}
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
String username = request.getParameter("username");
String password = request.getParameter("password");
User user = new User(username,password);
user.setUsername(username);
user.setPassword(password);
request.getSession().setAttribute("user",user);
response.sendRedirect(request.getContextPath() +"/index.jsp");
}
}
接着我們還需要一個頁面，用戶登錄成功頁面index.jsp
歡迎你： ${user.username }<a href="${pageContext.request.contextPath }/servlet/QuitServlet?username=${user.username }">退出</a>
這裏的退出是現實用戶的在線與離線狀態
現在我們需要監聽session中user對象的加入
package cn.class3g.web.listener;
import java.util.HashMap;
import java.util.Map;
import javax.servlet.ServletContext;
import javax.servlet.http.HttpSession;
import javax.servlet.http.HttpSessionAttributeListener;
import javax.servlet.http.HttpSessionBindingEvent;
import cn.class3g.web.domain.User;
public class SessionAttributeListener implements HttpSessionAttributeListener {
public void attributeAdded(HttpSessionBindingEvent se) {
// TODO Auto-generated method stub
Object obj = se.getValue();
if (obj instanceof User) {
HttpSession session = se.getSession();
ServletContext context = session.getServletContext();
Map map = (Map) context.getAttribute("map");
if (map == null) {
map = new HashMap();
context.setAttribute("map", map);
}
User user = (User) obj;
map.put(user.getUsername(), session);
}
}
public void attributeRemoved(HttpSessionBindingEvent se) {
// TODO Auto-generated method stub
}
public void attributeReplaced(HttpSessionBindingEvent se) {
// TODO Auto-generated method stub
}
}
接着需要建立一個用戶顯示界面listUser.jsp
<body>
當前用戶有：
<c:forEach var="me" items="${map }">
${me.key }
</c:forEach>
這裏我們需要用到標籤
因爲我們做的是一個在線用戶的查詢系統，所以我們要給用戶一個退出，來現實用戶的在線與離線QuitServlet
package cn.class3g.web.servlet;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.Map;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
public class QuitServlet extends HttpServlet {
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
String username = request.getParameter("username");
Map map = (Map) this.getServletContext().getAttribute("map");
HttpSession session = (HttpSession) map.get(username);
if(session !=null){
session.invalidate();
map.remove(username);
}
request.getRequestDispatcher("/quit.jsp").forward(request, response);
}
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
this.doGet(request, response);
}
}