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JavaWeb MVC 實戰：Servlet+JSP+JavaBean 實現用戶註冊登錄完整項目

編輯：Java 相關知識

項目架構

me.gacl.domain      → 實體類
me.gacl.dao         → 數據訪問接口
me.gacl.dao.impl    → DAO 實現
me.gacl.service     → 業務接口
me.gacl.service.impl→ Service 實現
me.gacl.web.controller → Servlet 控制器
me.gacl.web.UI      → 頁面跳轉 Servlet
me.gacl.web.formbean→ 表單驗證 Bean
me.gacl.util        → 工具類
me.gacl.exception   → 自定義異常

核心模塊代碼

1. 實體類

public class User implements Serializable {
    private String id;        // UUID
    private String userName;
    private String userPwd;
    private String email;
    private Date birthday;
    // getter/setter
}

2. DAO 層（XML 文件存儲）

public class UserDaoImpl implements IUserDao {
    // 使用 Dom4j + XPath 操作 DB.xml
    public User find(String userName, String userPwd) {
        Document doc = XmlUtils.getDocument();
        Element e = (Element) doc.selectSingleNode(
            "//user[@userName='"+userName+"' and @userPwd='"+userPwd+"']");
        // 映射到 User 對象...
    }
    public void add(User user) {
        // 添加節點並寫回 XML
    }
}

3. Service 層（業務邏輯 + 異常）

public class UserServiceImpl implements IUserService {
    private IUserDao dao = new UserDaoImpl();
    
    public void registerUser(User user) throws UserExistException {
        if (dao.find(user.getUserName()) != null) 
            throw new UserExistException("用戶名已存在");
        dao.add(user);
    }
    
    public User loginUser(String name, String pwd) {
        return dao.find(name, pwd);
    }
}

4. 表單驗證 Bean（核心亮點）

public class RegisterFormBean {
    private String userName, userPwd, confirmPwd, email, birthday;
    private Map<String, String> errors = new HashMap<>();
    
    public boolean validate() {
        boolean ok = true;
        if (empty(userName)) { ok=false; errors.put("userName","用戶名不能為空"); }
        else if (!userName.matches("[a-zA-Z]{4,12}")) { ok=false; errors.put("userName","4-12位字母"); }
        if (empty(userPwd)) { ok=false; errors.put("userPwd","密碼不能為空"); }
        else if (!userPwd.matches("\\d{6,12}")) { ok=false; errors.put("userPwd","6-12位數字"); }
        if (!userPwd.equals(confirmPwd)) { ok=false; errors.put("confirmPwd","兩次密碼不一致"); }
        if (!empty(email) && !email.matches("\\w+@\\w+(\\.\\w+)+")) 
            { ok=false; errors.put("email","郵箱格式錯誤"); }
        // 生日驗證...
        return ok;
    }
    // getter/setter
}

5. WebUtils 工具類（自動封裝）

public class WebUtils {
    public static <T> T requestBean(HttpServletRequest req, Class<T> clazz) {
        T bean = clazz.newInstance();
        Enumeration<String> en = req.getParameterNames();
        while (en.hasMoreElements()) {
            String name = en.nextElement();
            BeanUtils.setProperty(bean, name, req.getParameter(name));
        }
        return bean;
    }
    public static String makeId() { return UUID.randomUUID().toString(); }
}

6. 控制器 Servlet


// 註冊控制器
public class RegisterServlet extends HttpServlet {
    protected void doGet(req, resp) {
        RegisterFormBean form = WebUtils.requestBean(req, RegisterFormBean.class);
        if (!form.validate()) {
            req.setAttribute("formbean", form);  // 回顯數據與錯誤
            forward("/WEB-INF/pages/register.jsp");
            return;
        }
        User user = new User();
        BeanUtils.copyProperties(user, form);
        user.setId(WebUtils.makeId());
        try {
            new UserServiceImpl().registerUser(user);
            showMsg("註冊成功", "/servlet/LoginUIServlet");
        } catch (UserExistException e) {
            form.getErrors().put("userName", e.getMessage());
            req.setAttribute("formbean", form);
            forward("/WEB-INF/pages/register.jsp");
        }
    }
}

// 登錄控制器
public class LoginServlet extends HttpServlet {
    protected void doGet(req, resp) {
        User user = new UserServiceImpl().loginUser(
            req.getParameter("username"), req.getParameter("password"));
        if (user == null) { showMsg("用戶名或密碼錯誤", "/servlet/LoginUIServlet"); return; }
        req.getSession().setAttribute("user", user);  // 存入 Session
        showMsg("登錄成功", "/index.jsp");
    }
}

// 註銷控制器
public class LogoutServlet extends HttpServlet {
    protected void doGet(req, resp) {
        req.getSession().removeAttribute("user");
        showMsg("註銷成功", "/servlet/LoginUIServlet");
    }
}

7. JSP 頁面（EL 表達式回顯）

<input type="text" name="userName" value="${formbean.userName}">
${formbean.errors.userName}
<input type="password" name="userPwd" value="${formbean.userPwd}">
${formbean.errors.userPwd}