通讯录系统数据库设计与实现

1. 数据库设计与配置1.1 数据库建表 SQL-- 创建数据库使用UTF-8编码 CREATE DATABASE IF NOT EXISTS contact_system DEFAULT CHARACTER SET utf8mb4 DEFAULT COLLATE utf8mb4_unicode_ci; USE contact_system; -- 用户表 CREATE TABLE users ( id INT PRIMARY KEY AUTO_INCREMENT COMMENT 用户ID, user_name VARCHAR(50) NOT NULL UNIQUE COMMENT 用户名, password VARCHAR(50) NOT NULL COMMENT 密码明文存储便于调试, create_time TIMESTAMP DEFAULT CURRENT_TIMESTAMP COMMENT 创建时间 ) ENGINEInnoDB DEFAULT CHARSETutf8mb4 COMMENT用户表; -- 联系人表 CREATE TABLE tb_contact ( id INT PRIMARY KEY AUTO_INCREMENT COMMENT 联系人ID, name VARCHAR(50) NOT NULL COMMENT 姓名, phone VARCHAR(20) NOT NULL COMMENT 电话, email VARCHAR(100) COMMENT 邮箱, group_name ENUM(家人,同事,朋友,其他) DEFAULT 其他 COMMENT 分组, remark VARCHAR(500) COMMENT 备注, create_time TIMESTAMP DEFAULT CURRENT_TIMESTAMP COMMENT 添加时间, user_id INT NOT NULL COMMENT 所属用户ID, FOREIGN KEY (user_id) REFERENCES users(id) ON DELETE CASCADE ) ENGINEInnoDB DEFAULT CHARSETutf8mb4 COMMENT联系人表; -- 插入测试数据 INSERT INTO users (user_name, password) VALUES (admin, 123456), (user1, 123456); INSERT INTO tb_contact (name, phone, email, group_name, remark, user_id) VALUES (张三, 13800138000, zhangsanexample.com, 同事, 技术部同事, 1), (李四, 13900139000, lisiexample.com, 朋友, 大学同学, 1), (王五, 13600136000, wangwuexample.com, 家人, 父亲, 2);1.2 Navicat 连接步骤打开Navicat点击连接 → MySQL配置连接参数连接名任意如ContactSystem主机localhost本地或远程IP端口3306默认用户名root或自定义用户密码数据库密码点击测试连接成功后点击确定双击新创建的连接右键选择运行SQL文件执行上述建表SQL2. 项目结构搭建2.1 标准项目目录结构ContactSystem/ ├── src/ │ ├── entity/ │ │ ├── Users.java │ │ └── Contact.java │ ├── servlet/ │ │ ├── LoginServlet.java │ │ ├── LogoutServlet.java │ │ ├── AddContactServlet.java │ │ ├── UpdateContactServlet.java │ │ ├── DeleteContactServlet.java │ │ └── SelectContactServlet.java │ ├── service/ │ │ ├── UserBo.java │ │ └── ContactBo.java │ ├── dao/ │ │ ├── DBUtil.java │ │ ├── UserDao.java │ │ └── ContactDao.java │ └── common/ │ └── Validate.java ├── WebContent/ │ ├── WEB-INF/ │ │ ├── lib/ │ │ │ └── mysql-connector-java-8.0.xx.jar │ │ └── web.xml │ ├── login.jsp │ ├── index.jsp │ ├── addContact.jsp │ ├── editContact.jsp │ └── contactList.jsp └── 项目配置文件2.2 IDEA项目创建步骤打开IDEA → File → New → Project选择Java Enterprise → Web Application项目名ContactSystem不使用MavenApplication Server选择Tomcat 9.x创建完成后手动创建上述目录结构下载MySQL驱动jar包放入WEB-INF/lib目录3. 核心代码实现3.1 实体类entity层Users.javapackage entity; import java.util.Date; public class Users { private int id; private String userName; private String password; private Date createTime; // 构造方法 public Users() {} public Users(String userName, String password) { this.userName userName; this.password password; } // Getter和Setter方法 public int getId() { return id; } public void setId(int id) { this.id id; } public String getUserName() { return userName; } public void setUserName(String userName) { this.userName userName; } public String getPassword() { return password; } public void setPassword(String password) { this.password password; } public Date getCreateTime() { return createTime; } public void setCreateTime(Date createTime) { this.createTime createTime; } }Contact.javapackage entity; import java.util.Date; public class Contact { private int id; private String name; private String phone; private String email; private String groupName; private String remark; private Date createTime; private int userId; // 构造方法 public Contact() {} public Contact(String name, String phone, String email, String groupName, String remark, int userId) { this.name name; this.phone phone; this.email email; this.groupName groupName; this.remark remark; this.userId userId; } // Getter和Setter方法略参考Users.java格式 }3.2 数据库工具类dao层DBUtil.javapackage dao; import java.sql.*; public class DBUtil { private static final String DRIVER com.mysql.cj.jdbc.Driver; private static final String URL jdbc:mysql://localhost:3306/contact_system?useUnicodetruecharacterEncodingUTF-8serverTimezoneAsia/Shanghai; private static final String USERNAME root; private static final String PASSWORD 你的数据库密码; // 加载数据库驱动 static { try { Class.forName(DRIVER); } catch (ClassNotFoundException e) { e.printStackTrace(); } } // 获取数据库连接 public static Connection getConnection() throws SQLException { return DriverManager.getConnection(URL, USERNAME, PASSWORD); } // 关闭资源 public static void close(Connection conn, Statement stmt, ResultSet rs) { try { if (rs ! null) rs.close(); if (stmt ! null) stmt.close(); if (conn ! null) conn.close(); } catch (SQLException e) { e.printStackTrace(); } } // 开启事务 public static void beginTransaction(Connection conn) throws SQLException { if (conn ! null) { conn.setAutoCommit(false); } } // 提交事务 public static void commitTransaction(Connection conn) throws SQLException { if (conn ! null) { conn.commit(); } } // 回滚事务 public static void rollbackTransaction(Connection conn) { try { if (conn ! null) { conn.rollback(); } } catch (SQLException e) { e.printStackTrace(); } } }3.3 数据访问层dao层UserDao.javapackage dao; import entity.Users; import java.sql.*; public class UserDao { // 用户登录验证 public Users login(String userName, String password) { Connection conn null; PreparedStatement pstmt null; ResultSet rs null; Users user null; try { conn DBUtil.getConnection(); // 使用PreparedStatement防止SQL注入 String sql SELECT id, user_name, password FROM users WHERE user_name ? AND password ?; pstmt conn.prepareStatement(sql); pstmt.setString(1, userName); pstmt.setString(2, password); rs pstmt.executeQuery(); if (rs.next()) { user new Users(); user.setId(rs.getInt(id)); user.setUserName(rs.getString(user_name)); user.setPassword(rs.getString(password)); } } catch (SQLException e) { e.printStackTrace(); } finally { DBUtil.close(conn, pstmt, rs); } return user; } // 用户注册扩展功能 public boolean register(Users user) { Connection conn null; PreparedStatement pstmt null; boolean success false; try { conn DBUtil.getConnection(); String sql INSERT INTO users (user_name, password) VALUES (?, ?); pstmt conn.prepareStatement(sql); pstmt.setString(1, user.getUserName()); pstmt.setString(2, user.getPassword()); int rows pstmt.executeUpdate(); success rows 0; } catch (SQLException e) { e.printStackTrace(); } finally { DBUtil.close(conn, pstmt, null); } return success; } }ContactDao.javapackage dao; import entity.Contact; import java.sql.*; import java.util.ArrayList; import java.util.List; public class ContactDao { // 添加联系人 public boolean addContact(Contact contact) { Connection conn null; PreparedStatement pstmt null; boolean success false; try { conn DBUtil.getConnection(); String sql INSERT INTO tb_contact (name, phone, email, group_name, remark, user_id) VALUES (?, ?, ?, ?, ?, ?); pstmt conn.prepareStatement(sql); pstmt.setString(1, contact.getName()); pstmt.setString(2, contact.getPhone()); pstmt.setString(3, contact.getEmail()); pstmt.setString(4, contact.getGroupName()); pstmt.setString(5, contact.getRemark()); pstmt.setInt(6, contact.getUserId()); int rows pstmt.executeUpdate(); success rows 0; } catch (SQLException e) { e.printStackTrace(); } finally { DBUtil.close(conn, pstmt, null); } return success; } // 分页查询联系人 public ListContact getContactsByPage(int userId, int page, int pageSize, String keyword) { ListContact contacts new ArrayList(); Connection conn null; PreparedStatement pstmt null; ResultSet rs null; try { conn DBUtil.getConnection(); StringBuilder sql new StringBuilder( SELECT * FROM tb_contact WHERE user_id ? ); // 添加搜索条件 if (keyword ! null !keyword.trim().isEmpty()) { sql.append( AND (name LIKE ? OR phone LIKE ? OR email LIKE ?)); } sql.append( ORDER BY create_time DESC LIMIT ?, ?); pstmt conn.prepareStatement(sql.toString()); int paramIndex 1; pstmt.setInt(paramIndex, userId); if (keyword ! null !keyword.trim().isEmpty()) { String likeKeyword % keyword %; pstmt.setString(paramIndex, likeKeyword); pstmt.setString(paramIndex, likeKeyword); pstmt.setString(paramIndex, likeKeyword); } pstmt.setInt(paramIndex, (page - 1) * pageSize); pstmt.setInt(paramIndex, pageSize); rs pstmt.executeQuery(); while (rs.next()) { Contact contact new Contact(); contact.setId(rs.getInt(id)); contact.setName(rs.getString(name)); contact.setPhone(rs.getString(phone)); contact.setEmail(rs.getString(email)); contact.setGroupName(rs.getString(group_name)); contact.setRemark(rs.getString(remark)); contact.setCreateTime(rs.getTimestamp(create_time)); contact.setUserId(rs.getInt(user_id)); contacts.add(contact); } } catch (SQLException e) { e.printStackTrace(); } finally { DBUtil.close(conn, pstmt, rs); } return contacts; } // 获取联系人总数用于分页 public int getContactCount(int userId, String keyword) { Connection conn null; PreparedStatement pstmt null; ResultSet rs null; int count 0; try { conn DBUtil.getConnection(); StringBuilder sql new StringBuilder( SELECT COUNT(*) FROM tb_contact WHERE user_id ? ); if (keyword ! null !keyword.trim().isEmpty()) { sql.append( AND (name LIKE ? OR phone LIKE ? OR email LIKE ?)); } pstmt conn.prepareStatement(sql.toString()); int paramIndex 1; pstmt.setInt(paramIndex, userId); if (keyword ! null !keyword.trim().isEmpty()) { String likeKeyword % keyword %; pstmt.setString(paramIndex, likeKeyword); pstmt.setString(paramIndex, likeKeyword); pstmt.setString(paramIndex, likeKeyword); } rs pstmt.executeQuery(); if (rs.next()) { count rs.getInt(1); } } catch (SQLException e) { e.printStackTrace(); } finally { DBUtil.close(conn, pstmt, rs); } return count; } // 其他CRUD方法updateContact、deleteContact、getContactById略参考上述方法实现 }3.4 业务逻辑层service层UserBo.javapackage service; import dao.UserDao; import entity.Users; public class UserBo { private UserDao userDao new UserDao(); // 用户登录业务逻辑 public Users login(String userName, String password) { // 参数校验 if (userName null || userName.trim().isEmpty() || password null || password.trim().isEmpty()) { return null; } // 调用DAO层进行验证 return userDao.login(userName.trim(), password.trim()); } // 用户注册业务逻辑 public boolean register(Users user) { // 业务规则校验 if (user.getUserName() null || user.getUserName().trim().isEmpty() || user.getPassword() null || user.getPassword().trim().isEmpty()) { return false; } // 用户名长度限制 if (user.getUserName().length() 3 || user.getUserName().length() 20) { return false; } return userDao.register(user); } }ContactBo.javapackage service; import dao.ContactDao; import entity.Contact; import java.util.List; public class ContactBo { private ContactDao contactDao new ContactDao(); // 添加联系人业务逻辑 public boolean addContact(Contact contact) { // 参数校验 if (contact null || contact.getName() null || contact.getName().trim().isEmpty() || contact.getPhone() null || contact.getPhone().trim().isEmpty()) { return false; } // 手机号格式校验 if (!contact.getPhone().matches(^1[3-9]\\d{9}$)) { return false; } // 邮箱格式校验可选 if (contact.getEmail() ! null !contact.getEmail().trim().isEmpty()) { if (!contact.getEmail().matches(^[A-Za-z0-9_.-][A-Za-z0-9.-]$)) { return false; } } return contactDao.addContact(contact); } // 分页查询联系人 public ListContact getContactsByPage(int userId, int page, int pageSize, String keyword) { // 参数校验 if (userId 0 || page 0 || pageSize 0) { return null; } // 限制最大页数 if (pageSize 100) { pageSize 100; } return contactDao.getContactsByPage(userId, page, pageSize, keyword); } // 获取总页数 public int getTotalPages(int userId, int pageSize, String keyword) { int total contactDao.getContactCount(userId, keyword); return (int) Math.ceil((double) total / pageSize); } }3.5 工具类common层Validate.javapackage common; import javax.servlet.http.HttpServletRequest; public class Validate { // 检查字符串是否为空或null public static boolean isEmpty(String str) { return str null || str.trim().isEmpty(); } // 检查手机号格式 public static boolean isPhoneValid(String phone) { if (isEmpty(phone)) return false; return phone.matches(^1[3-9]\\d{9}$); } // 检查邮箱格式 public static boolean isEmailValid(String email) { if (isEmpty(email)) return false; return email.matches(^[A-Za-z0-9_.-][A-Za-z0-9.-]$); } // 防止XSS攻击过滤特殊字符 public static String filterXSS(String input) { if (isEmpty(input)) return input; return input.replaceAll(, lt;) .replaceAll(, gt;) .replaceAll(\, quot;) .replaceAll(, #x27;) .replaceAll(/, #x2F;); } // 从请求参数中安全获取值 public static String getParameter(HttpServletRequest request, String paramName) { String value request.getParameter(paramName); if (value ! null) { value filterXSS(value.trim()); } return value; } }3.6 Servlet控制器servlet层LoginServlet.javapackage servlet; import entity.Users; import service.UserBo; import javax.servlet.*; import javax.servlet.http.*; import javax.servlet.annotation.*; import java.io.IOException; WebServlet(/LoginServlet) public class LoginServlet extends HttpServlet { private UserBo userBo new UserBo(); Override protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { // 设置编码兼容GB2312和UTF-8 request.setCharacterEncoding(UTF-8); response.setContentType(text/html;charsetUTF-8); // 获取参数 String userName request.getParameter(userName); String password request.getParameter(password); // 参数校验 if (userName null || userName.trim().isEmpty() || password null || password.trim().isEmpty()) { request.setAttribute(error, 用户名和密码不能为空); request.getRequestDispatcher(login.jsp).forward(request, response); return; } // 业务处理 Users user userBo.login(userName, password); if (user ! null) { // 登录成功创建Session HttpSession session request.getSession(); session.setAttribute(user, user); session.setMaxInactiveInterval(30 * 60); // 30分钟超时 // 重定向到首页 response.sendRedirect(index.jsp); } else { // 登录失败安全提示 request.setAttribute(error, 用户名或密码错误); request.getRequestDispatcher(login.jsp).forward(request, response); } } Override protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { // 防止直接访问 response.sendRedirect(login.jsp); } }SelectContactServlet.javapackage servlet; import entity.Contact; import entity.Users; import service.ContactBo; import javax.servlet.*; import javax.servlet.http.*; import javax.servlet.annotation.*; import java.io.IOException; import java.util.List; WebServlet(/SelectContactServlet) public class SelectContactServlet extends HttpServlet { private ContactBo contactBo new ContactBo(); Override protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { // 登录拦截检查 HttpSession session request.getSession(false); if (session null || session.getAttribute(user) null) { response.sendRedirect(login.jsp); return; } // 设置编码 request.setCharacterEncoding(UTF-8); response.setContentType(text/html;charsetUTF-8); // 获取当前用户 Users user (Users) session.getAttribute(user); int userId user.getId(); // 获取分页参数 String pageStr request.getParameter(page); String keyword request.getParameter(keyword); int page 1; int pageSize 10; if (pageStr ! null !pageStr.trim().isEmpty()) { try { page Integer.parseInt(pageStr); if (page 1) page 1; } catch (NumberFormatException e) { page 1; } } // 获取搜索关键词 if (keyword ! null) { keyword keyword.trim(); } // 查询数据 ListContact contacts contactBo.getContactsByPage(userId, page, pageSize, keyword); int totalPages contactBo.getTotalPages(userId, pageSize, keyword); // 设置请求属性 request.setAttribute(contacts, contacts); request.setAttribute(currentPage, page); request.setAttribute(totalPages, totalPages); request.setAttribute(keyword, keyword); // 转发到列表页面 request.getRequestDispatcher(contactList.jsp).forward(request, response); } }3.7 JSP页面实现login.jsp% page contentTypetext/html;charsetUTF-8 languagejava % html head title通讯录管理系统 - 登录/title style body { font-family: Arial, sans-serif; background: #f5f5f5; } .login-box { width: 300px; margin: 100px auto; padding: 20px; background: white; border-radius: 5px; box-shadow: 0 0 10px rgba(0,0,0,0.1); } .form-group { margin-bottom: 15px; } label { display: block; margin-bottom: 5px; } input { width: 100%; padding: 8px; box-sizing: border-box; } .error { color: red; font-size: 12px; } .btn { width: 100%; padding: 10px; background: #007bff; color: white; border: none; border-radius: 3px; cursor: pointer; } /style /head body div classlogin-box h2用户登录/h2 form actionLoginServlet methodpost div classform-group label用户名:/label input typetext nameuserName required /div div classform-group label密码:/label input typepassword namepassword required /div div classform-group button typesubmit classbtn登录/button /div % if (request.getAttribute(error) ! null) { % div classerror% request.getAttribute(error) %/div % } % /form p测试账号admin/123456 或 user1/123456/p /div /body /htmlindex.jsp% page contentTypetext/html;charsetUTF-8 languagejava % % page importentity.Users % % // 登录检查 Users user (Users) session.getAttribute(user); if (user null) { response.sendRedirect(login.jsp); return; } % html head title通讯录管理系统 - 首页/title style body { font-family: Arial, sans-serif; margin: 0; padding: 20px; } .header { background: #007bff; color: white; padding: 10px; margin-bottom: 20px; } .menu a { margin-right: 15px; color: #007bff; text-decoration: none; } .welcome { float: right; } /style /head body div classheader h1通讯录管理系统/h1 div classwelcome 欢迎% user.getUserName() % | a hrefLogoutServlet stylecolor: white;退出登录/a /div /div div classmenu a hrefSelectContactServlet联系人列表/a a hrefaddContact.jsp添加联系人/a /div div classcontent h2系统功能/h2 ul li联系人管理增删改查/li li联系人分组家人/同事/朋友/其他/li li分页显示和搜索功能/li li用户会话管理/li /ul /div /body /htmlcontactList.jsp% page contentTypetext/html;charsetUTF-8 languagejava % % page importentity.Contact, java.util.List % % // 登录检查 if (session.getAttribute(user) null) { response.sendRedirect(login.jsp); return; } ListContact contacts (ListContact) request.getAttribute(contacts); Integer currentPage (Integer) request.getAttribute(currentPage); Integer totalPages (Integer) request.getAttribute(totalPages); String keyword (String) request.getAttribute(keyword); if (keyword null) keyword ; % html head title联系人列表/title style table { width: 100%; border-collapse: collapse; margin-top: 20px; } th, td { border: 1px solid #ddd; padding: 8px; text-align: left; } th { background-color: #f2f2f2; } .pagination { margin-top: 20px; } .search-box { margin-bottom: 20px; } /style /head body h2联系人列表/h2 div classsearch-box form actionSelectContactServlet methodget input typetext namekeyword value% keyword % placeholder搜索姓名/电话/邮箱 button typesubmit搜索/button a hrefaddContact.jsp添加联系人/a /form /div table tr th姓名/th th电话/th th邮箱/th th分组/th th备注/th th操作/th /tr % if (contacts ! null !contacts.isEmpty()) { for (Contact contact : contacts) { % tr td% contact.getName() %/td td% contact.getPhone() %/td td% contact.getEmail() ! null ? contact.getEmail() : %/td td% contact.getGroupName() %/td td% contact.getRemark() ! null ? contact.getRemark() : %/td td a hrefeditContact.jsp?id% contact.getId() %编辑/a a hrefDeleteContactServlet?id% contact.getId() % onclickreturn confirm(确定删除吗)删除/a /td /tr % } } else { % tr td colspan6 styletext-align: center;暂无联系人数据/td /tr % } % /table % if (totalPages ! null totalPages 0) { % div classpagination % for (int i 1; i totalPages; i) { if (i currentPage) { % span% i %/span % } else { % a hrefSelectContactServlet?page% i %keyword% keyword %% i %/a % } } % /div % } % pa hrefindex.jsp返回首页/a/p /body /html3.8 web.xml配置?xml version1.0 encodingUTF-8? web-app xmlnshttp://xmlns.jcp.org/xml/ns/javaee xmlns:xsihttp://www.w3.org/2001/XMLSchema-instance xsi:schemaLocationhttp://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_4_0.xsd version4.0 !-- 字符编码过滤器 -- filter filter-nameCharacterEncodingFilter/filter-name filter-classfilter.CharacterEncodingFilter/filter-class init-param param-nameencoding/param-name param-valueUTF-8/param-value /init-param /filter filter-mapping filter-nameCharacterEncodingFilter/filter-name url-pattern/*/url-pattern /filter-mapping !-- 登录拦截过滤器 -- filter filter-nameLoginFilter/filter-name filter-classfilter.LoginFilter/filter-class /filter filter-mapping filter-nameLoginFilter/filter-name url-pattern/contactList.jsp/url-pattern url-pattern/addContact.jsp/url-pattern url-pattern/editContact.jsp/url-pattern url-pattern/SelectContactServlet/url-pattern url-pattern/AddContactServlet/url-pattern url-pattern/UpdateContactServlet/url-pattern url-pattern/DeleteContactServlet/url-pattern /filter-mapping !-- Servlet映射 -- servlet servlet-nameLoginServlet/servlet-name servlet-classservlet.LoginServlet/servlet-class /servlet servlet-mapping servlet-nameLoginServlet/servlet-name url-pattern/LoginServlet/url-pattern /servlet-mapping servlet servlet-nameSelectContactServlet/servlet-name servlet-classservlet.SelectContactServlet/servlet-class /servlet servlet-mapping servlet-nameSelectContactServlet/servlet-name url-pattern/SelectContactServlet/url-pattern /servlet-mapping !-- 欢迎页面 -- welcome-file-list welcome-filelogin.jsp/welcome-file /welcome-file-list !-- 会话超时配置30分钟 -- session-config session-timeout30/session-timeout /session-config /web-app4. Tomcat部署与配置4.1 Tomcat 9.x部署步骤下载Tomcat 9.x从Apache官网下载Tomcat 9.x压缩包解压到指定目录如D:\apache-tomcat-9.0.x环境变量配置新建CATALINA_HOME值为Tomcat安装目录在Path中添加%CATALINA_HOME%\bin启动Tomcat# Windows %CATALINA_HOME%\bin\startup.bat # Linux/Mac $CATALINA_HOME/bin/startup.sh验证启动访问http://localhost:8080看到Tomcat首页即成功4.2 IDEA项目部署配置TomcatRun → Edit Configurations → 点击 → Tomcat Server → Local配置Tomcat Home目录Deployment标签页添加Artifact项目部署配置File → Project Structure → Artifacts点击 → Web Application: Exploded → From Modules选择项目模块设置Output directory运行项目点击Run按钮启动Tomcat访问http://localhost:8080/ContactSystem/login.jsp5. 常见问题排查方案5.1 404错误问题原因解决方案URL路径错误检查web.xml中的servlet映射配置项目未正确部署检查Tomcat的webapps目录是否有项目文件夹文件路径错误确保JSP文件在WebContent目录下上下文路径错误检查IDEA中Deployment的Application Context设置5.2 登录失败问题问题现象排查步骤提示用户名或密码错误1. 检查数据库用户数据2. 查看控制台SQL日志3. 验证UserDao.login方法登录后Session丢失1. 检查session.setMaxInactiveInterval设置2. 验证web.xml中session-timeout配置密码验证失败1. 检查数据库密码字段长度2. 验证密码是否包含特殊字符5.3 乱码问题乱码场景解决方案表单提交中文乱码Servlet中添加request.setCharacterEncoding(UTF-8)数据库读取乱码连接URL添加characterEncodingUTF-8参数JSP页面显示乱码页面顶部添加% page contentTypetext/html;charsetUTF-8 %响应乱码Servlet中添加response.setContentType(text/html;charsetUTF-8)5.4 SQL连接问题// 常见连接错误排查 public static void testConnection() { try { Connection conn DBUtil.getConnection(); if (conn ! null !conn.isClosed()) { System.out.println(数据库连接成功); conn.close(); } } catch (SQLException e) { System.err.println(连接失败 e.getMessage()); // 检查1. MySQL服务是否启动 2. 用户名密码是否正确 3. 数据库名是否正确 } }5.5 Tomcat启动失败端口占用检查8080端口是否被占用参考来源Java Web实现用户登录功能【JAVA项目实战】【图书管理系统】用户查询功能【Servlet】【Jsp】【Mysql】java web简单的注册登录界面实现(servletmysqljspidea)jspdaobeanservletMVC模式实现简单用户登录和注册页面连接数据库登录页面包含验证码两周内免登陆等功能IDEAJavaJSPMysqlTomcat实现Web学生信息管理系统JSPservletJDBC实现简单的注册登录功能