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"%>

<%request.setCharacterEncoding("utf-8");%>

<%
    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";
        
    }
%>


    
        
        
    
    
        
请输入你的登录信息
        
<%=request.getAttribute("errMsg") == null ? "" : request.getAttribute("errMsg")%>
        

            
账号：
                
                    > <%=option1%>
                    ><%=option2%>
                
            
            
口令： />
            

        
    

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()) {
            
            out.println("");
            out.println("");
            out.println("");
            out.println("");
            out.println("");
            out.println("");
            out.println("Servlet Checklogin at " + request.getContextPath() + "");
            out.println("");
            out.println("");
        }
    }

    // 
    
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        processRequest(request, response);
    }

    
    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        processRequest(request, response);
    }

    
    @Override
    public String getServletInfo() {
        return "Short description";
    }// 

}

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;
    }

    
    public String getPwd() {
        return pwd;
    }

    
    public void setPwd(String pwd) {
        this.pwd = pwd;
    }

    
    public String getUid() {
        return uid;
    }

    
    public void setUid(String uid) {
        this.uid = uid;
    }

}

admin.jsp

<%@page contentType="text/html" pageEncoding="UTF-8"%>



    
        
        
    
    
        
登录成功！
你的登录账号是：
            
        
        

        

            程序制作人信息:

            姓名：以太潮汐

        
    

运行结果