基於 Hibernate + Struts + MyEclipse 構建 Blog 系統實戰：配置、DAO、Session 管理完整代碼

項目技術棧

• IDE：MyEclipse 3.6 (內建 Spring/Hibernate/Struts 向導)
• 框架：Struts 1.x + Hibernate 2.x/3.x (早期版本，`net.sf.hibernate` 包名)
• 數據庫：MySQL (JDBC 驅動 `org.gjt.mm.mysql.Driver`)
• 構建：Ant (MyEclipse 管理)

核心配置：hibernate.cfg.xml

<hibernate-configuration>
  <session-factory>
    <!-- 連接屬性 -->
    <property name="connection.username">root</property>
    <property name="connection.url">jdbc:mysql://localhost:3306/tonnyblog</property>
    <property name="dialect">net.sf.hibernate.dialect.MySQLDialect</property>
    <property name="connection.password"></property>
    <property name="connection.driver_class">org.gjt.mm.mysql.Driver</property>

    <!-- 映射文件 -->
    <mapping resource="com/tonny/blog/bean/User.hbm.xml"/>
    <mapping resource="com/tonny/blog/bean/Item.hbm.xml"/>
    <mapping resource="com/tonny/blog/bean/Review.hbm.xml"/>
  </session-factory>
</hibernate-configuration>

SessionFactory 單例工具類 (ThreadLocal 綁定 Session)

package com.tonny.blog.util;

import net.sf.hibernate.*;
import net.sf.hibernate.cfg.Configuration;

public class HibernateUtil {
    private static final SessionFactory sessionFactory;
    private static final ThreadLocal threadSession = new ThreadLocal<>();

    static {
        try {
            sessionFactory = new Configuration().configure().buildSessionFactory();
        } catch (HibernateException ex) {
            throw new RuntimeException("構建 SessionFactory 失敗", ex);
        }
    }

    private HibernateUtil() {}

    public static Session getSession() throws HibernateException {
        Session s = threadSession.get();
        if (s == null || !s.isOpen()) {
            s = sessionFactory.openSession();
            threadSession.set(s);
        }
        return s;
    }

    public static void closeSession() throws HibernateException {
        Session s = threadSession.get();
        threadSession.set(null);
        if (s != null && s.isOpen()) s.close();
    }

    public static SessionFactory getSessionFactory() {
        return sessionFactory;
    }
}

實體映射示例 (User.hbm.xml)

<hibernate-mapping>
  <class name="com.tonny.blog.bean.User" table="t_user">
    <id name="id" column="user_id">
      <generator class="native"/>
    </id>
    <property name="username" column="username" not-null="true" unique="true"/>
    <property name="password" column="password" not-null="true"/>
    <property name="email" column="email"/>
    <property name="regDate" column="reg_date" type="timestamp"/>
  </class>
</hibernate-mapping>

DAO 基類與具體實現

// 通用基類
public abstract class BaseDAO {
    protected Session getSession() throws HibernateException {
        return HibernateUtil.getSession();
    }
    protected void closeSession() throws HibernateException {
        HibernateUtil.closeSession();
    }
}

// UserDAO
public class UserDAO extends BaseDAO {
    public User findByUsername(String username) {
        Session s = getSession();
        try {
            Query q = s.createQuery("from User u where u.username = :name");
            q.setString("name", username);
            return (User) q.uniqueResult();
        } finally {
            closeSession();
        }
    }
    
    public void save(User user) {
        Session s = getSession();
        Transaction tx = null;
        try {
            tx = s.beginTransaction();
            s.save(user);
            tx.commit();
        } catch (Exception e) {
            if (tx != null) tx.rollback();
            throw e;
        } finally {
            closeSession();
        }
    }
}

Struts Action 整合示例

public class RegisterAction extends Action {
    public ActionForward execute(ActionMapping mapping, ActionForm form,
                                 HttpServletRequest request, HttpServletResponse response) {
        RegisterForm rf = (RegisterForm) form;
        User user = new User();
        user.setUsername(rf.getUsername());
        user.setPassword(rf.getPassword());
        user.setEmail(rf.getEmail());
        user.setRegDate(new Date());
        
        UserDAO dao = new UserDAO();
        try {
            dao.save(user);
            request.setAttribute("msg", "註冊成功！");
            return mapping.findForward("success");
        } catch (Exception e) {
            e.printStackTrace();
            request.setAttribute("msg", "註冊失敗：" + e.getMessage());
            return mapping.findForward("failure");
        }
    }
}

關鍵最佳實踐總結

1. Session 管理：`ThreadLocal` 綁定「一請求一 Session」，`Filter`/`Interceptor` 統一開啟/提交/關閉 (Open Session in View)
2. 事務邊界：Service 層管理事務，DAO 僅負責 CRUD，避免業務邏輯分散在 Action 中
3. 映射文件：每個實體獨立 `.hbm.xml`，便於維護與團隊協作
4. 異常處理：捕獲 `HibernateException` 轉換為業務異常，確保事務回滾與 Session 關閉
5. 性能優化：二級緩存 (Ehcache)、延遲加載 (`lazy="true"`)、批量抓取 (`batch-size`)、查詢緩存

現代化遷移指引

結語

這個 Blog 系統展示了 **Struts + Hibernate 黃金組合** 在 2004-2008 年構建企業級 Web 應用的標準範式：分層架構、ORM 映射、Session 管理、事務控制。雖然具體 API 已歷經數代更迭，但 **分層解耦、ORM 思想、聲明式事務、緩存策略** 等核心工程智慧始終貫穿至今的 Spring Boot / Quarkus / Micronaut 等現代框架中。