Hibernate + MySQL 入門實戰：從配置到 CRUD 完整流程

Hibernate 核心優勢

• 對象關係映射 (ORM)：用面向對象方式操作數據庫，消除 JDBC 樣板代碼。
• 輕量級封裝：核心 Jar 約 10MB，依賴少，上手快。
• 無侵入性：實體類為純 POJO，不依賴 Hibernate API。
• 可移植性：切換數據庫只需修改方言配置。

環境依賴

<dependencies>
  <dependency><groupId>org.hibernate</groupId><artifactId>hibernate-core</artifactId><version>5.6.15.Final</version></dependency>
  <dependency><groupId>mysql</groupId><artifactId>mysql-connector-java</artifactId><version>8.0.33</version></dependency>
  <dependency><groupId>org.slf4j</groupId><artifactId>slf4j-simple</artifactId><version>2.0.9</version></dependency>
</dependencies>

核心配置文件

1. hibernate.cfg.xml

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-configuration PUBLIC
  "-//Hibernate/Hibernate Configuration DTD 3.0//EN"
  "https://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd">
<hibernate-configuration>
  <session-factory>
    <property name="hibernate.connection.driver_class">com.mysql.cj.jdbc.Driver</property>
    <property name="hibernate.connection.url">jdbc:mysql://localhost:3306/hibernate_first?useSSL=false&serverTimezone=UTC</property>
    <property name="hibernate.connection.username">root</property>
    <property name="hibernate.connection.password">ab12</property>
    <property name="hibernate.dialect">org.hibernate.dialect.MySQL8Dialect</property>
    <property name="hibernate.show_sql">true</property>
    <property name="hibernate.format_sql">true</property>
    <property name="hibernate.hbm2ddl.auto">update</property> <!-- 自動建表/更新 -->
    <mapping resource="com/hibernate/User.hbm.xml"/>
  </session-factory>
</hibernate-configuration>

2. 實體類 User.java

package com.hibernate;
import java.util.Date;

public class User {
    private String id;
    private String name;
    private String password;
    private Date createTime;
    private Date expireTime;
    // Getter/Setter 省略
}

3. 映射文件 User.hbm.xml

<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC
  "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
  "https://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping>
  <class name="com.hibernate.User" table="t_user">
    <id name="id">
      <generator class="uuid"/>
    </id>
    <property name="name"/>
    <property name="password"/>
    <property name="createTime"/>
    <property name="expireTime"/>
  </class>
</hibernate-mapping>

工具類與測試

1. HibernateUtil（單例 SessionFactory）

package com.hibernate.util;
import org.hibernate.SessionFactory;
import org.hibernate.cfg.Configuration;

public class HibernateUtil {
    private static final SessionFactory SESSION_FACTORY = buildSessionFactory();
    private static SessionFactory buildSessionFactory() {
        try { return new Configuration().configure().buildSessionFactory(); }
        catch (Throwable ex) { throw new ExceptionInInitializerError(ex); }
    }
    public static SessionFactory getSessionFactory() { return SESSION_FACTORY; }
    public static void shutdown() { getSessionFactory().close(); }
}

2. 自動建表 ExportDB.java

package com.hibernate;
import org.hibernate.cfg.Configuration;
import org.hibernate.tool.hbm2ddl.SchemaExport;

public class ExportDB {
    public static void main(String[] args) {
        Configuration cfg = new Configuration().configure();
        new SchemaExport(cfg).create(true, true); // 輸出 SQL 並執行
    }
}

3. CRUD 測試 Client.java

package com.hibernate;
import org.hibernate.Session;
import org.hibernate.Transaction;
import java.util.Date;

public class Client {
    public static void main(String[] args) {
        Session session = HibernateUtil.getSessionFactory().openSession();
        Transaction tx = null;
        try {
            tx = session.beginTransaction();
            // 新增
            User user = new User();
            user.setName("張三");
            user.setPassword("123");
            user.setCreateTime(new Date());
            session.save(user); // 持久化
            tx.commit();
            System.out.println("保存成功，ID: " + user.getId());

            // 查詢
            User loaded = session.get(User.class, user.getId());
            System.out.println("查詢: " + loaded.getName());

            // 修改
            tx = session.beginTransaction();
            loaded.setPassword("456");
            session.update(loaded);
            tx.commit();

            // 刪除
            tx = session.beginTransaction();
            session.delete(loaded);
            tx.commit();
        } catch (Exception e) {
            if (tx != null) tx.rollback();
            e.printStackTrace();
        } finally {
            session.close();
            HibernateUtil.shutdown();
        }
    }
}

關鍵概念深度解析

• 三大狀態：Transient (瞬時) → Persistent (持久) → Detached (游離)。save() 使對象變為持久狀態，事務提交時自動同步到數據庫。
• Session 緩存：一級緩存，同一 Session 內多次 get() 同一 ID 只發一條 SQL。
• hbm2ddl.auto：create (每次重建)、update (更新)、validate (驗證)、none (禁用)。生產環境建議用 Flyway/Liquibase 管理遷移。

總結

Hibernate 以「配置映射、操作對象、自動生成 SQL」極大提升開發效率。掌握「配置 → 映射 → SessionFactory → Session → Transaction → CRUD」核心鏈路，理解對象三大狀態轉換與緩存機制，即可駕輕就熟處理企業級持久層開發。