package com.gwssi.listener;import javax.servlet.http.HttpSession;import javax.servlet.http.HttpSessionEvent;import javax.servlet.http.HttpSessionListener;public class SessionListener implements HttpSessionListener {	@Override	public void sessionCreated(HttpSessionEvent event) {		HttpSession session = event.getSession();		SessionBean sessionBean = SessionFactory.getInstance().getSessionBean();		System.out.println("sessionCreated session: " + (session.getId()));		System.out.println("sessionCreated accessCount: "				+ (sessionBean.getAccessCount()));		// 访问次数		sessionBean.setAccessCount(sessionBean.getAccessCount() + 1);		// 在线人数统计		sessionBean.getOnline().put(session.getId(), null);	}	@Override	public void sessionDestroyed(HttpSessionEvent event) {		HttpSession session = event.getSession();		SessionFactory factory = SessionFactory.getInstance();		SessionBean sessionBean = factory.getSessionBean();		System.out.println("sessionDestroyed session: " + (session.getId()));		System.out.println("sessionDestroyed accessCount: "				+ (sessionBean.getAccessCount()));		factory.removeLogin(session);	}}

package com.gwssi.listener;import javax.servlet.http.HttpSession;public class SessionFactory {	private SessionBean sessionBean = new SessionBean();	private static SessionFactory factory;	private SessionFactory() {	}	static {		factory = new SessionFactory();	}	public synchronized static SessionFactory getInstance() {		if (factory == null) {			factory = new SessionFactory();		}		return factory;	}	public void addLogin(HttpSession session, String user) {		this.getSessionBean().getOnline().put(session.getId(), user);		this.getSessionBean().getLogin().add(user);	}	public void removeLogin(HttpSession session) {		this.getSessionBean().getLogin()				.remove(this.getSessionBean().getOnline().get(session.getId()));		this.getSessionBean().getOnline().remove(session.getId());	}	public boolean isOnline(String user) {		return this.getSessionBean().getLogin().contains(user);	}	public SessionBean getSessionBean() {		return sessionBean;	}	public void setSessionBean(SessionBean sessionBean) {		this.sessionBean = sessionBean;	}}

package com.gwssi.listener;import java.util.HashMap;import java.util.HashSet;import java.util.Map;import java.util.Set;public class SessionBean {	private Map<String, String> online = new HashMap<String, String>();	private int accessCount = 0;	private Set<String> login = new HashSet<String>();	/**	 * 	 * 返回当前系统在线人数	 * 	 * @return int	 */	public int getOnlineCount() {		return this.online.size();	}	/**	 * 返回当前系统登录人数	 * 	 * @return int	 */	public int getLoginCount() {		return this.getLogin().size();	}	public Map<String, String> getOnline() {		return online;	}	public void setOnline(Map<String, String> online) {		this.online = online;	}	public int getAccessCount() {		return accessCount;	}	public void setAccessCount(int accessCount) {		this.accessCount = accessCount;	}	public Set<String> getLogin() {		return login;	}	public void setLogin(Set<String> login) {		this.login = login;	}}

 <session-config>        <session-timeout>10</session-timeout>    </session-config>        <listener>    	<listener-class>com.gwssi.listener.SessionListener</listener-class>    </listener>

	//添加进入SessionFactory，以供记录是否在线				SessionFactory.getInstance().addLogin(session, userInfo.getUserId());

package com.gwssi.filter;import java.io.IOException;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 cn.gwssi.csdb.fbk.util.StringUtil;public class SessionCheckFilter implements Filter {	@Override	public void destroy() {	}	@Override	public void doFilter(ServletRequest req, ServletResponse res,			FilterChain chain) throws IOException, ServletException {		HttpServletRequest request = (HttpServletRequest) req;		String userid = request.getParameter("userid");//		System.out.println(request.getServletPath() + "===SessionCheckFilter====" + userid);		if (StringUtil.isEmpty(userid) || "null".equals(userid)) {			// 当请求中没有userid参数时，由后台进行判断			chain.doFilter(req, res);		} else {			HttpSession session = request.getSession();			UserInfo userInfo = (UserInfo) session.getAttribute("userInfo");			HttpServletResponse response = (HttpServletResponse) res;			if (userInfo == null) {				// session过期				redirect(request, response);			} else {				System.out.println(userInfo.getUserId() + "========" + userid);				if (userid.equals(userInfo.getUserId())) {					chain.doFilter(req, res);				} else {					// 登录名不一致					redirect(request, response);				}			}		}	}	private void redirect(HttpServletRequest request,			HttpServletResponse response) throws IOException {		String requestType = request.getHeader("X-Requested-With");		if (requestType != null && requestType.equals("XMLHttpRequest")) {			response.setStatus(HttpServletResponse.SC_FORBIDDEN);		} else {			String href = http://www.mamicode.com/request.getContextPath()"/pages/sessionTimeOut.jsp";			response.sendRedirect(href);		}	}	@Override	public void init(FilterConfig config) throws ServletException {	}}

<filter>    	<filter-name>sessionCheckFilter</filter-name>    	<filter-class>com.gwssi.csdb.fbk.authority.SessionCheckFilter</filter-class>    </filter>    <filter-mapping>    	<filter-name>sessionCheckFilter</filter-name>    	<url-pattern>*.do</url-pattern>    </filter-mapping>