【Hibernate3】(1)初識Hibernate

一. 搭建環境

創建一個工程，需要到如以下的jar包：

還需要配置文件log4j.properties和hibernate.cfg.xml。

這個是hibernate.cfg.xml的內容：

<!DOCTYPE hibernate-configuration PUBLIC
	"-//Hibernate/Hibernate Configuration DTD 3.0//EN"
	"http://www.hibernate.org/dtd/hibernate-configuration-3.0.dtd">

<hibernate-configuration>
	<session-factory>
		<property name="hibernate.connection.driver_class">com.mysql.jdbc.Driver</property>
		<property name="hibernate.connection.url">jdbc:mysql://localhost:3306/hibernate?createDatabaseIfNotExist=true</property>
		<property name="hibernate.connection.username">root</property>
		<property name="hibernate.connection.password">123456</property>
		<property name="hibernate.dialect">org.hibernate.dialect.MySQLDialect</property>
		<property name="show_sql">true</property>
		<mapping resource="org/hibernate/test/legacy/Simple.hbm.xml" />
	</session-factory>
</hibernate-configuration>

dialect和show_sql是指定了顯示什麼方言和在控制檯顯示sql語句。

二. 第一個程序

創建實體類User，具有以下屬性：

	private int id;
	private String username;
	private String sex;
	private int age;
	private Date birthday;
	private double salary;

創建User.hbm.xml文件，將其放在與實體同一級目錄下：

<?xml version="1.0"?>
<!-- ~ Hibernate, Relational Persistence for Idiomatic Java ~ ~ License: 
	GNU Lesser General Public License (LGPL), version 2.1 or later. ~ See the 
	lgpl.txt file in the root directory or <http://www.gnu.org/licenses/lgpl-2.1.html>. -->
<!DOCTYPE hibernate-mapping PUBLIC
        "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
        "http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd">

<hibernate-mapping package="org.hibernate.test.abstractembeddedcomponents.cid">

	<class name="com.thr.hibernate.entity.User" table="T_USER">
		<id name="id">
			<generator class="native"></generator>
		</id>
		<property name="username" />
		<property name="sex" />
		<properties name="age" />
		<property name="birthday" />
		<property name="salary" />
	</class>


</hibernate-mapping>

class配置實體類的全名，table配置數據庫表明，id表示的是主鍵，其它的是User的屬性。
最後將創建好的User.hbm.xml配置到hibernate.cfg.xml文件中：

		<property name="hbm2ddl.auto">update</property>
		<mapping resource="com/thr/hibernate/entity/User.hbm.xml" />

配置hbm2ddl.auto的參數update表示如果表不存在的情況下，自動創建表；存在的話就自動更新。

創建測試類測試一下：

1. 添加

	public void test1() {
		User user = new User();
		user.setUsername("張三");
		user.setSex("男");
		user.setAge(27);
		user.setBirthday(new Date());
		user.setSalary(100.5);

		// 解析hibernate.cfg.xml配置文件
		Configuration cfg = new Configuration().configure();
		// 創建SessionFactory（創建連接池）
		SessionFactory factory = cfg.buildSessionFactory();
		// 創建Session
		Session session = factory.openSession();
		// 創建及開啓事務對象
		Transaction trans = null;
		try {
			trans = session.beginTransaction();
			// 添加User實體對象
			session.save(user);
			trans.commit();
		} catch (HibernateException e) {
			trans.rollback();
			e.printStackTrace();
		} finally {
			if (session != null) {
				session.close();
			}
		}
	}

2. 查詢

	/**
	 * 根據ID查詢
	 */
	public void testQuery() {

		// 解析hibernate.cfg.xml配置文件
		Configuration cfg = new Configuration().configure();
		// 創建SessionFactory（創建連接池）
		SessionFactory factory = cfg.buildSessionFactory();
		// 創建Session
		Session session = factory.openSession();
		// 創建及開啓事務對象
		Transaction trans = null;
		try {
			trans = session.beginTransaction();
			User user = (User) session.load(User.class, 1);
			System.out.println(user);
			trans.commit();
		} catch (HibernateException e) {
			trans.rollback();
			e.printStackTrace();
		} finally {
			if (session != null) {
				session.close();
			}
		}
	}

3. 刪除

	/**
	 * 根據ID刪除
	 */
	public void testDelete() {

		// 解析hibernate.cfg.xml配置文件
		Configuration cfg = new Configuration().configure();
		// 創建SessionFactory（創建連接池）
		SessionFactory factory = cfg.buildSessionFactory();
		// 創建Session
		Session session = factory.openSession();
		// 創建及開啓事務對象
		Transaction trans = null;
		try {
			trans = session.beginTransaction();
			User user = (User) session.load(User.class, 1);
			session.delete(user);
			System.out.println(user);
			trans.commit();
		} catch (HibernateException e) {
			trans.rollback();
			e.printStackTrace();
		} finally {
			if (session != null) {
				session.close();
			}
		}
	}

4. 更新

	/**
	 * 根據ID更新
	 */
	public void testUpdate() {
		// 解析hibernate.cfg.xml配置文件
		Configuration cfg = new Configuration().configure();
		// 創建SessionFactory（創建連接池）
		SessionFactory factory = cfg.buildSessionFactory();
		// 創建Session
		Session session = factory.openSession();
		// 創建及開啓事務對象
		Transaction trans = null;
		try {
			trans = session.beginTransaction();
			User user = (User) session.load(User.class, 2);
			user.setSex("女");
			user.setUsername("小雪");
			session.update(user);
			trans.commit();
		} catch (HibernateException e) {
			trans.rollback();
			e.printStackTrace();
		} finally {
			if (session != null) {
				session.close();
			}
		}
	}

5. 查詢集合

	/**
	 * 查詢集合
	 */
	public void testQueryAll() {
		// 解析hibernate.cfg.xml配置文件
		Configuration cfg = new Configuration().configure();
		// 創建SessionFactory（創建連接池）
		SessionFactory factory = cfg.buildSessionFactory();
		// 創建Session
		Session session = factory.openSession();
		// 創建及開啓事務對象
		Transaction trans = null;
		try {
			trans = session.beginTransaction();
			Query query = session.createQuery("from User");
			List<User> users = query.list();
			for (User user : users) {
				System.out.println(user);
			}
			trans.commit();
		} catch (HibernateException e) {
			trans.rollback();
			e.printStackTrace();
		} finally {
			if (session != null) {
				session.close();
			}
		}
	}