同一账号，后一用户登录，前一个用户则被踢掉
原理：将已登录用户保存在数据库或者application或静态List(Map)里，
主要保存 session对象，登录账号id 等
每一个用户进行登录时去查看是否已经登陆过，
如果已登录，则取出其session然后将登陆账号id从session里移除
在过滤器里进行登录与否的判断
下面是一些详细步骤：
1、登录页面 login.jsp
<%@ page language="java" contentType="text/html; charset=utf-8" pageEncoding="utf-8"%> <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> <html> <head> <meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1"> <title>Insert title here</title> </head> <body> <center> <h1>用户登录</h1> <hr> <form action="LoginServlet"> <table> <tr><th> 用户名：</th><td><input type="text" name="username"/></td></tr> <tr><th> 密码：</th><td> <input type="password" name="password"/></td></tr> <tr><td></td><td> <input type="submit" value="登录"></td></tr> </table> <br> <br> </form> </center> </body> </html>
2、main_frame.jsp 登录成功后的主页面
<%@ page language="java" contentType="text/html; charset=utf-8" pageEncoding="utf-8"%> <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> <html> <head> <meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1"> <title>Insert title here</title> </head> <body> <% String name = (String)request.getSession().getAttribute("username"); %> 欢迎你，<%=name%> <a href="ManyServlet">操作一下</a> </body> </html>
3、session过期(未登陆)的页面 session.jsp
<%@ page language="java" contentType="text/html; charset=utf-8" pageEncoding="utf-8"%> <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> <html> <head> <meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1"> <title>Insert title here</title> </head> <body> 会话已过期 </body> <script type="text/javascript"> setTimeout(function (){ window.location.href = "${pageContext.request.contextPath}/login.jsp"; window.close(); }, 2000); </script> </html>
4、被踢下线的页面 multisession.jsp
<%@ page language="java" contentType="text/html; charset=utf-8" pageEncoding="utf-8"%> <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> <html> <head> <meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1"> <title>Insert title here</title> </head> <body> 你的账号在别处登录，你已被迫下线。 </body> <script type="text/javascript"> setTimeout(function (){ window.location.href = "<%=request.getContextPath()%>/login.jsp"; }, 2000); </script> </html>
5、进行登录的servlet
package session; import java.io.IOException; import java.io.PrintWriter; import java.util.HashMap; 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; /** * Servlet implementation class LoginServlet */ public class LoginServlet extends HttpServlet { private static final long serialVersionUID = 1L; private Map<String, HttpSession> userMap = new HashMap<String, HttpSession>(); /** * @see HttpServlet#HttpServlet() */ public LoginServlet() { super(); // TODO Auto-generated constructor stub } /** * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response) */ protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { String username = request.getParameter("username"); String password = request.getParameter("password"); HttpSession session = request.getSession(); request.getSession().setAttribute("username", username); if(!userMap.containsKey(username)) { System.out.println("新的会话ID:"+session.getId()); userMap.put(username, session); }else { HttpSession session2 = userMap.get(username); if(!session2.getId().equals(session.getId())) { System.out.println("新的会话ID:"+session.getId()); System.out.println("session已失效"); System.out.println("已失效Id:" + session2.getId()); session2.removeAttribute("username"); session2.setAttribute("usermsg", "yes"); userMap.put(username, session); } } String url = "main_frame.jsp"; response.sendRedirect(url); } /** * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response) */ protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { // TODO Auto-generated method stub doGet(request, response); } }
6、过滤器 SessionFilter.java
package filter; import java.io.IOException; import java.util.StringTokenizer; import javax.servlet.Filter; import javax.servlet.FilterChain; import javax.servlet.FilterConfig; import javax.servlet.ServletException; import javax.servlet.ServletRequest; import javax.servlet.ServletResponse; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import javax.servlet.http.HttpSession; import com.utils.SysUtils; /** * Servlet Filter implementation class SessionFilter */ public class SessionFilter implements Filter { protected boolean ignore = false; //忽略 protected String noFilterPath; //不过滤的路径 protected String sessionTimeoutPage; //Session过期转向的页面 /** * Default constructor. */ public SessionFilter() { // TODO Auto-generated constructor stub } /** * @see Filter#destroy() */ public void destroy() { // TODO Auto-generated method stub } /** * @see Filter#doFilter(ServletRequest, ServletResponse, FilterChain) */ public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException { // TODO Auto-generated method stub // place your code here // pass the request along the filter chain if(this.ignore) { chain.doFilter(request, response); return; } HttpServletRequest req = (HttpServletRequest) request; HttpServletResponse resp= (HttpServletResponse) response; HttpSession session = req.getSession(); String username = (String) session.getAttribute("username"); boolean isLogin = username!=null; if(!isLogin) { String servletPath = req.getServletPath(); //当前服务端路径 if(!isMatchPath(noFilterPath, servletPath)) //如果不匹配则转到Login页面 { String url = req.getRequestURI() + (req.getQueryString() != null ? "?" + req.getQueryString() : ""); if(session.getAttribute("usermsg")!= null&&!session.getAttribute("usermsg").equals("") ) { resp.sendRedirect(req.getContextPath()+"/multisession.jsp"); return; } resp.sendRedirect(req.getContextPath()+"/session.jsp"); System.out.println("Session is timeout. 地址为：" + url); return; } } chain.doFilter(request, response); } /** * @see Filter#init(FilterConfig) */ public void init(FilterConfig fConfig) throws ServletException { // TODO Auto-generated method stub this.ignore = "true".equalsIgnoreCase(fConfig.getInitParameter("ignore")); this.noFilterPath = fConfig.getInitParameter("noFilterPath"); } /** * 是否匹配过虑路径 * * @param filterPath 过滤路径 * @param path 访问的地址 * @return 匹配返回true，否则返回false */ public boolean isMatchPath(String filterPath, String path) { /* StringTokenizer token = new StringTokenizer(filterPath, path); while(token.hasMoreTokens()) { String patter = SysUtils.trim(token.nextToken()); boolean match = SysUtils.wildcardMatch(patter, path); if(match) { return true; } } return false;*/ if(filterPath.contains(path)) { return true; } return false; } }
7、进行额外业务servlet ManyServlet.java
package session; import java.io.IOException; import javax.servlet.ServletException; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; /** * Servlet implementation class ManyServlet */ public class ManyServlet extends HttpServlet { private static final long serialVersionUID = 1L; /** * @see HttpServlet#HttpServlet() */ public ManyServlet() { super(); // TODO Auto-generated constructor stub } /** * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response) */ protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { // TODO Auto-generated method stub System.out.println("业务逻辑哈哈"); String url = "haha.jsp"; response.sendRedirect(url); } /** * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response) */ protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { // TODO Auto-generated method stub doGet(request, response); } }
对应的jsp haha.jsp
<%@ page language="java" contentType="text/html; charset=utf-8" pageEncoding="utf-8"%> <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> <html> <head> <meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1"> <title>Insert title here</title> </head> <body> 嘿，你好。 </body> </html>
web.xml 中fileter的配置
<filter> <filter-name>SessionFilter</filter-name> <filter-class>filter.SessionFilter</filter-class> <init-param> <param-name>ignore</param-name> <param-value>false</param-value> </init-param> <init-param> <param-name>sessionTimeoutPage</param-name> <param-value>/error.jsp</param-value> </init-param> <init-param> <param-name>noFilterPath</param-name> <param-value>/login.jsp, /LoginServlet, /session.jsp, /multisession.jsp, /index.jsp </param-value> </init-param> </filter> <filter-mapping> <filter-name>SessionFilter</filter-name> <url-pattern>*.jsp</url-pattern> </filter-mapping> <filter-mapping> <filter-name>SessionFilter</filter-name> <url-pattern>*</url-pattern> </filter-mapping>
