Hibernate之hello world

1. 包含hibernate庫

使用maven

<!-- hibernate -->
<dependency>
    <groupId>org.hibernate</groupId>
    <artifactId>hibernate-core</artifactId>
    <version>5.0.1.Final</version>
</dependency>

不使用maven
hibernate官網：http://hibernate.org/orm/，將下載的jar包放到lib目錄下。

2. 配置hibernate

在class目錄下新建配置文件：hibernate.cfg.xml

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-configuration PUBLIC
          "-//Hibernate/Hibernate Configuration DTD 3.0//EN"
          "http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd">
<hibernate-configuration>
   <session-factory>
        <!-- 配置數據源 -->
        <property name="connection.url">jdbc:mysql://localhost:3306/yourDatabaseName?characterEncoding=UTF-8</property>
        <property name="connection.username">root</property>
        <property name="connection.password">123456</property>
        <property name="connection.driver_class">com.mysql.jdbc.Driver</property>
        <property name="dialect">org.hibernate.dialect.MySQL5Dialect</property>
        <property name="show_sql">true</property>
        <property name="current_session_context_class">thread</property>
        <!-- hibernate啓動時自動創建表：將update改爲create -->
        <property name="hbm2ddl.auto">update</property>

        <!-- 需要映射的類 -->
        <mapping class="com.yourPackage.ClassA"/>
        <mapping class="com.yourPackage.ClassB"/>

   </session-factory>
</hibernate-configuration>

3. 使用hibernate

3.1 新建HibernateUtil類

public class HibernateUtil {

    private static final SessionFactory sessionFactory;
    private static Logger log;

    static {
        try {
            // Create the SessionFactory from hibernate.cfg.xml
            sessionFactory = new Configuration().configure().buildSessionFactory();
        } catch (Throwable ex) {
            // Make sure you log the exception, as it might be swallowed
            System.err.println("Initial SessionFactory creation failed." + ex);
            throw new ExceptionInInitializerError(ex);
        }
    }

    public static SessionFactory getSessionFactory() {
        return sessionFactory;
    }

}

HibernateUtil類用於獲取sessionFactory，之後在代碼中就可以這樣獲取session：

Session session = HibernateUtil.getSessionFactory().getCurrentSession();

3.2 新建java類：User

package com.yourPackage;

// 註解@Entity和@Table表示這是一個實體類，映射到表：tb_user
@Entity
@Table(name = "tb_user")
public class User{
    // Column表示將屬性映射到表的userName列。屬性名和列名相同時，可以省略註解
    @Column（name="userName"）
    private String userName;

    @Column（name="password"）
    private String password;

    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;
    }
}

使用註解的方式，需要在hibernate.cfg.xml中聲明映射類：

<hibernate-configuration>
   <session-factory>
        ...
        ...

        <!-- 需要映射的類 -->
        <mapping class="com.yourPackage.User"/>
        ...
   </session-factory>
</hibernate-configuration>

3.3 在MySQL中創建相應的表：tb_user

3.4 向表中新增一個用戶

User user = new User();
user.setUserName("jack");
user.setPassword("123456");

Session session = HibernateUtil.getSessionFactory().getCurrentSession();
try {
    session.beginTransaction();          // 開啓事務
    session.persist(user);               // 保存對象
    session.getTransaction().commit();
} catch (Exception e) {
    session.getTransaction().rollback();
}