Hibernate组件（Component）映射

组件(Component)映射

Component（组件）是一个被包含的对象,它作为值类型被持久化，而非一个被引用的实体。“component(组件)”这一术语指的是面向对象的合成概念（而并不是系统构架层次上的组件的概念）。在hibernate中可借助Component节点的定义，完成对复杂数据表的细分。在hibernate语义中，将某个实例对象中的一个逻辑组成称为Component(组件)。Component(组件)与实体对象的根本差别就在于Componet(组件)没有标识符（identity），它作为一个逻辑组成完全从属于实体对象。

还是以我第一个hibernate实例为例来说明组件映射：

User实体类如下：

package eg;
public class User {

    private int id;
    private Name name;//Name是另一个类
    private Date birthday;
       //setter和getter方法省略
}

package eg;
public class User {
	
	private int id;
	private Name name;//Name是另一个类
	private Date birthday;
       //setter和getter方法省略
}

 Name类如下：

package eg;
public class Name {

    private String firstName;
    private String lastName;

  //省略setter和getter方法
}

package eg;
public class Name {

    private String firstName;
    private String lastName;

  //省略setter和getter方法
}

 User.hbm.xml映射文件如下：

<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC
    "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
    "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping>
    <class name="eg.User" >
        <id name="id" >
            <generator class="native" />
        </id>
        <component name="name">
            <property name="firstName" column="first_name" />
            <property name="lastName" column="last_name" />
        </component>
        <property name="birthday" />
    </class>
</hibernate-mapping

<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC
    "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
    "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping>
    <class name="eg.User" >
        <id name="id" >
            <generator class="native" />
        </id>
        <component name="name">
            <property name="firstName" column="first_name" />
            <property name="lastName" column="last_name" />
        </component>
        <property name="birthday" />
    </class>
</hibernate-mapping

 测试类如下：

public class TestUser {

    @Test
    public void test1(){
        Configuration config = new Configuration();
        config.configure();
        SessionFactory factory = config.buildSessionFactory();

        Session session = factory.openSession();
        Transaction tran = session.beginTransaction();
        User user = new User();
        Name name = new Name();
        name.setFirstName("long");
        name.setLastName("xiao");
        user.setName(name);
        user.setBirthday(new Date());
        session.save(user);
        tran.commit();
        session.close();
    }
}

public class TestUser {

	@Test
	public void test1(){
		Configuration config = new Configuration();
		config.configure();
		SessionFactory factory = config.buildSessionFactory();
	
		Session session = factory.openSession();
		Transaction tran = session.beginTransaction();
		User user = new User();
		Name name = new Name();
		name.setFirstName("long");
		name.setLastName("xiao");
		user.setName(name);
		user.setBirthday(new Date());
		session.save(user);
		tran.commit();
		session.close();
	}
}

 测试程序运行后，数据库中生成了user表，创建语句如下：

DROP TABLE IF EXISTS `test`.`user`;
CREATE TABLE  `test`.`user` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `first_name` varchar(255) DEFAULT NULL,
  `last_name` varchar(255) DEFAULT NULL,
  `birthday` datetime DEFAULT NULL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=2 DEFAULT CHARSET=utf8;

DROP TABLE IF EXISTS `test`.`user`;
CREATE TABLE  `test`.`user` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `first_name` varchar(255) DEFAULT NULL,
  `last_name` varchar(255) DEFAULT NULL,
  `birthday` datetime DEFAULT NULL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=2 DEFAULT CHARSET=utf8;

 数据库中记录如下所示：

+----+------------+-----------+----------+
| id | first_name | last_name | birthday |
+----+------------+-----------+----------+
|  1 | long       | xiao      | NULL     |
+----+------------+-----------+----------+
1 row in set (0.00 sec)

评论

1 楼 kxhu 2014-04-21  

请教component配置对应的批注是？谢谢！