Servlet登陆功能的实现

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（1）创建动态的Login页面

//登陆界面package com.lc;import javax.servlet.http.*;import java.io.*;public class Login extends HttpServlet{public void doGet(HttpServletRequest req,HttpServletResponse res){//业务逻辑try{//解决中文乱码res.setContentType("text/html;charset=gbk");PrintWriter pw = res.getWriter();//返回登陆界面pw.println("<html>");pw.println("<body>");pw.println("<h1>用户登录</h1>");pw.println("<form action=logincl method=post>");  //action的是servlet的urlpw.println("用户名：<input type=text name=username><br/>");pw.println("密码：<input type=password name=passwd><br/>");pw.println("<input type=submit value=loing><br/>");pw.println("</form>");pw.println("</body>");pw.println("</html>");}catch(Exception ex){ex.printStackTrace();}}public void doPost(HttpServletRequest req,HttpServletResponse res){this.doGet(req,res);}}

（2）创建接受Login的servlet

//登陆界面package com.lc;import javax.servlet.http.*;import java.io.*;public class Logincl extends HttpServlet{public void doGet(HttpServletRequest req,HttpServletResponse res){//业务逻辑try{//解决中文乱码//接受用户名和密码String u = req.getParameter("username");String p = req.getParameter("passwd");//验证if(u.equals("lc") && p.equals("123")){//合法的情况 跳转到Welcomeres.sendRedirect("welcome");//这里跳转的仍是servlet的url}else{//不合法的情况//跳转res.sendRedirect("login");//跳转的是要到servlet的url}}catch(Exception ex){ex.printStackTrace();}}public void doPost(HttpServletRequest req,HttpServletResponse res){this.doGet(req,res);}}

（3）登陆成功要跳转的welcome页面

//登陆界面package com.tsinghua;import javax.servlet.http.*;import java.io.*;public class Welcome extends HttpServlet{public void doGet(HttpServletRequest req,HttpServletResponse res){//业务逻辑try{//解决中文乱码res.setContentType("text/html;charset=gbk");PrintWriter pw = res.getWriter();pw.println("hello welcome！");}catch(Exception ex){ex.printStackTrace();}}public void doPost(HttpServletRequest req,HttpServletResponse res){this.doGet(req,res);}}

（4）配置文件web.xml的编写

<?xml version="1.0" encoding="ISO-8859-1"?><web-app xmlns="http://java.sun.com/xml/ns/javaee"  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"  xsi:schemaLocation="http://java.sun.com/xml/ns/javaee                      http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd"  version="3.0"  metadata-complete="true">  <display-name>Welcome to Tomcat</display-name>  <description>     Welcome to Tomcat  </description>  <!--JSP servlet mappings starts-->  <servlet>    <servlet-name>Login</servlet-name>    <servlet-class>com.lc.Login</servlet-class>  </servlet>   <servlet-mapping>    <servlet-name>Login</servlet-name>    <url-pattern>/login</url-pattern>  </servlet-mapping>  <servlet>    <servlet-name>Logincl</servlet-name>    <servlet-class>com.<span style="font-family:Arial, Helvetica, sans-serif;">lc</span>.Logincl</servlet-class>  </servlet>   <servlet-mapping>    <servlet-name>Logincl</servlet-name>    <url-pattern>/logincl</url-pattern>  </servlet-mapping>  <servlet>    <servlet-name>Welcome</servlet-name>    <servlet-class>com.lc.Welcome</servlet-class>  </servlet>   <servlet-mapping>    <servlet-name>Welcome</servlet-name>    <url-pattern>/welcome</url-pattern>  </servlet-mapping><!--JSP servlet mappings end--></web-app>

（5）运行结果：

5 1