根据你提供的需求，下面是一个实现示例，包括 login.jsp、FirstServlet 和 SecondServlet 的代码，以及如何处理错误页面。
1. 文件结构
web2024/│├── hw/│ ├── login.jsp│ ├── failed.jsp│├── WEB-INF/│ ├── userinfo.txt│ └── web.xml├── 404.html└── 500.html
2. userinfo.txt
在 WEB-INF/userinfo.txt 中存储用户信息，例如：
username1:password1username2:password2
3. login.jsp
<%@ page language="java" contentType="text/html; charset=UTF-8" pageEncoding="UTF-8"%><!DOCTYPE html><html><head><title>Login</title></head><body><h2>Login Page</h2><form action="<%= request.getContextPath() %>/servlet/firstServlet.do" method="post">Username: <input type="text" name="username"/><br/>Password: <input type="password" name="password"/><br/><input type="submit" value="Login"/></form></body></html>
4. FirstServlet.java
import javax.servlet.ServletException;import javax.servlet.annotation.WebServlet;import javax.servlet.http.HttpServlet;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;import java.io.BufferedReader;import java.io.IOException;import java.io.InputStreamReader;@WebServlet("/servlet/firstServlet.do")public class FirstServlet extends HttpServlet {protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {String username = request.getParameter("username");String password = request.getParameter("password");// 验证用户名和密码是否正确。boolean isValidUser = false;try (BufferedReader reader = new BufferedReader(new InputStreamReader(getServletContext().getResourceAsStream("/WEB-INF/userinfo.txt")))) {String line;while ((line = reader.readLine()) != null) {String[] parts = line.split(":");if (parts.length == 2 && parts[0].equals(username) && parts[1].equals(password)) {isValidUser = true;break;}}}if (isValidUser) {response.sendRedirect(request.getContextPath() + "/servlet/secondServlet.do?username=" + username);} else {response.sendRedirect(request.getContextPath() + "/hw/failed.jsp");}}protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {// 通常不支持 GET 请求，但可以重定向到登录页。response.sendRedirect(request.getContextPath() + "/hw/login.jsp");}}
5. SecondServlet.java
import javax.servlet.ServletException;import javax.servlet.annotation.WebServlet;import javax.servlet.http.HttpServlet;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;@WebServlet("/servlet/secondServlet.do")public class SecondServlet extends HttpServlet {protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {String username = request.getParameter("username");response.setContentType("text/html;charset=UTF-8");response.getWriter().println("<h1>Welcome, " + username + "!</h1>");}protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {// 不支持POST请求，这里可以重定向到其他地方或返回错误。doGet(request, response);}}
6. web.xml
<web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee"xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaeehttp://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd"version="3.1"><!-- 定义Error Pages --><error-page error-code="404"><location>/404.html</location></error-page><error-page error-code="500"><location>/500.html</location></error-page></web-app>
7. 错误页面 (404.html 和 500.html)
404.html
<!DOCTYPE html><html lang="en"><head><meta charset="UTF-8"><title>404 Not Found</title></head><body><h1>Error 404 - Page Not Found</h1><p>The page you are looking for does not exist.</p><a href="/web2024/hw/login.jsp">Go to Login Page</a></body></html>
500.html
<!DOCTYPE html><html lang="en"><head><meta charset="UTF-8"><title>500 Internal Server Error</title></head><body><h1>Error 500 - Internal Server Error</h1><p>An unexpected error occurred on the server.</p>// 可考虑输出异常信息，但需谨慎以免泄露敏感数据。<a href="/web2024/hw/login.jsp">Go to Login Page</a><!-- 提示出错信息 --><%String errorMessage = (String)request.getAttribute("javax.servlet.error.message");if(errorMessage != null){out.println("<p>Error details: " + errorMessage + "</p>");}%><!-- 提示用户联系管理员等 --><p>If the problem persists, please contact support.</p></body></html>
以上代码实现了你所要求的功能，包括用户登录验证、成功与失败的跳转、错误处理等。确保在Tomcat服务器中正确部署该Web应用程序，并根据需要调整路径和内容。
内容由零声教学AI助手提供，问题来源于学员提问
