首先写一个登陆界面----index.jsp
<body>
<form action="${pageContext.request.contextPath }/loginServlet" method="post">
用户名：<input name="uname"/><br/>
密码：<input name="pwd" type="password"/><br/>
<input type="submit" value="登录"/>
</form>
</body>
点击登陆,跳转至----loginServlet
@WebServlet(name="loginServlet",urlPatterns="/loginServlet") //Serclet3.0注解配置
public class LoginServlet extends HttpServlet {
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
String name = request.getParameter("uname"); //获取用户名
String pwd = request.getParameter("pwd"); //获取密码
if("jack".equals(name) && "bdqn".equals(pwd)){ //判断用户名与密码是否正确
request.getSession().setAttribute("name", name); //将name放到session作用域里
request.getRequestDispatcher("online.jsp").forward(request, response); //跳转至登录成功界面
}else if ("tom".equals(name) && "123".equals(pwd)) { //第二个用户
request.getSession().setAttribute("name", name);
request.getRequestDispatcher("online.jsp").forward(request, response);
}else {
request.getRequestDispatcher("401.jsp").forward(request, response); //如果未成功登录,跳转至401界面,可返回重新登录
}
}
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
doGet(request, response);
}
}
未成功登陆----401.jsp
<body>
请先登录，点击返回<a href="${pageContext.request.contextPath }/index.jsp">登录</a>页面
</body>
成功登录---online.jsp
<body>
登录成功！当前在线人数：${applicationScope.num } <!-- 监听器获取在线人数 -->
<a href="${pageContext.request.contextPath }/logoutServlet">退出</a>
</body>
退出处理----LogoutServlet
@WebServlet(name="logoutServlet",urlPatterns="/logoutServlet")
public class LogoutServlet extends HttpServlet {
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
request.getSession().removeAttribute("name");
request.getRequestDispatcher("index.jsp").forward(request, response);
}
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
doGet(request, response);
}
}
设置监听器----首先需要在web.xml里配置
<listener>
<listener-class>cn.bdqn.listener.DemoListemer</listener-class>
</listener>
监听器类 DemoListemer 继承 HttpSessionAttributeListener 接口
public class DemoListemer implements HttpSessionAttributeListener{
@Override
public void attributeAdded(HttpSessionBindingEvent event) {
int num=0; //定义初始在线人数为0
ServletContext servletContext = event.getSession().getServletContext();//使用session来判断是否为注册用户
Object object = servletContext.getAttribute("num"); //获取人数num
if(object==null){
num=1; //object为null,说明是第一个登录的用户
}else {
num=(Integer)object+1; //如果不为null,就在原人数上+1;
}
servletContext.setAttribute("num", num);
}
@Override
public void attributeRemoved(HttpSessionBindingEvent event) {
ServletContext servletContext = event.getSession().getServletContext();
Object object = servletContext.getAttribute("num"); //获取人数num
int num=(Integer)object-1; //退出登录后人数-1
servletContext.setAttribute("num", num); //变更人数后设置给num
}
@Override
public void attributeReplaced(HttpSessionBindingEvent event) {
// TODO Auto-generated method stub
}
}
登录成功页面图
时间： 2024-08-05 18:59:08