使用Servlet实现简单的登录验证

用户可以选择管理员和游客两种登录方式，管理员必须输入正确密码，游客不能输入任何密码

项目结构

index.jsp

<%@page contentType="text/html" pageEncoding="UTF-8"%>
<jsp:useBean id="userInfo" class="beans.UserBean" scope="session"/>
<%request.setCharacterEncoding("utf-8");%>
<jsp:setProperty name="userInfo" property="*"/>
<%String valueoption = (String) request.getAttribute("uid");String option1 = "管理员";String option2 = "游客";String valueoption1 = "admin";String valueoption2 = "guest";if ("guest".equals(valueoption)) {option1 = "游客";option2 = "管理员";valueoption1="guest";valueoption2="admin";}
%>
<!DOCTYPE html>
<html><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8"><title>系统登录</title></head><body><h1>请输入你的登录信息</h1><div style="color:red"><%=request.getAttribute("errMsg") == null ? "" : request.getAttribute("errMsg")%></div><form  method="POST" action="Checklogin"><p>账号：<select name="uid"  style="width: 100px"><option value= <%=valueoption1%>> <%=option1%></option><option value= <%=valueoption2%>><%=option2%></option></select></p><p>口令：<input   style="width: 100px" type="password" name="pwd" value=<%=request.getAttribute("pwd") == null ?"": request.getAttribute("pwd")%> /></p><div><input type="submit" value="确定" /></div></form></body>
</html>

Checklogin.java

package beans;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;public class Checklogin extends HttpServlet {protected void processRequest(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {response.setContentType("text/html;charset=UTF-8");request.setCharacterEncoding("utf-8");String uid = request.getParameter("uid");String pwd = request.getParameter("pwd");String errMsg = "";if ("admin".equals(uid)) {if ("1234567".equals(pwd)) {response.sendRedirect("admin.jsp");return;}errMsg = "管理员口令不正确！";request.setAttribute("uid", uid);request.setAttribute("pwd", pwd);request.setAttribute("errMsg",errMsg);request.getRequestDispatcher("index.jsp").forward(request,response);return;} else if ("guest".equals(uid)) {if (pwd == null || pwd.isEmpty()) {//口令不输入，得到的口令是长度为0的字符串//登录成功response.sendRedirect("admin.jsp");return;}errMsg = "游客不能也无需输入口令！";request.setAttribute("errMsg",errMsg);request.setAttribute("uid", uid);request.setAttribute("pwd", pwd);request.getRequestDispatcher("index.jsp").forward(request, response);return;}try (PrintWriter out = response.getWriter()) {/* TODO output your page here. You may use following sample code. */out.println("<!DOCTYPE html>");out.println("<html>");out.println("<head>");out.println("<title>Servlet Checklogin</title>");out.println("</head>");out.println("<body>");out.println("<h1>Servlet Checklogin at " + request.getContextPath() + "</h1>");out.println("</body>");out.println("</html>");}}// <editor-fold defaultstate="collapsed" desc="HttpServlet methods. Click on the + sign on the left to edit the code.">/*** Handles the HTTP <code>GET</code> method.** @param request servlet request* @param response servlet response* @throws ServletException if a servlet-specific error occurs* @throws IOException if an I/O error occurs*/@Overrideprotected void doGet(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {processRequest(request, response);}/*** Handles the HTTP <code>POST</code> method.** @param request servlet request* @param response servlet response* @throws ServletException if a servlet-specific error occurs* @throws IOException if an I/O error occurs*/@Overrideprotected void doPost(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {processRequest(request, response);}/*** Returns a short description of the servlet.** @return a String containing servlet description*/@Overridepublic String getServletInfo() {return "Short description";}// </editor-fold>}

UserBean.java

package beans;public class UserBean {private String pwd;private String uid;public UserBean() {}public UserBean(String pwd, String uid) {this.pwd = pwd;this.uid = uid;}/*** @return the pwd*/public String getPwd() {return pwd;}/*** @param pwd the pwd to set*/public void setPwd(String pwd) {this.pwd = pwd;}/*** @return the uid*/public String getUid() {return uid;}/*** @param uid the uid to set*/public void setUid(String uid) {this.uid = uid;}}

admin.jsp

<%@page contentType="text/html" pageEncoding="UTF-8"%>
<jsp:useBean id="userInfo" class="beans.UserBean" scope="session"/>
<!DOCTYPE html>
<html><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8"><title>系统管理</title></head><body><h1>登录成功！<br>你的登录账号是：<jsp:getProperty name="userInfo" property="uid"/></h1><br><p>程序制作人信息:<br>姓名：以太潮汐<br></p></body>
</html>

运行结果

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