Hibernate (10) _ one association map

This series of blog summarized here: Hibernate Summary

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Source project file: hibernate4.3_05 & hibernate4.3_06

One to one association mapping

FIG class:

relational tables:

1. Create a model class

IdCard have to give this a primary key, and specify one to one relationship.

package com.wyx.hiber.model;

public class IDCard
{

	/**
	 * 提供身份证的主键
	 */
	private Integer cardId;

	private String cardNo;

	/**
	 * 在身份证的类中有一个员工的属性，体现一对一
	 */
	private Emp emp;

	public Integer getCardId()
	{
		return cardId;
	}

	public void setCardId(Integer cardId)
	{
		this.cardId = cardId;
	}

	public String getCardNo()
	{
		return cardNo;
	}

	public void setCardNo(String cardNo)
	{
		this.cardNo = cardNo;
	}

	public Emp getEmp()
	{
		return emp;
	}

	public void setEmp(Emp emp)
	{
		this.emp = emp;
	}

	@Override
	public String toString()
	{
		return "IDCard [cardId=" + cardId + ", cardNo=" + cardNo + "]";
	}

}

2, configuration mapping file

<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC
        "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
        "http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd">
<hibernate-mapping package="com.wyx.hiber.model">
	<class name="IDCard" table="t_id_card">
		<!-- 指定主键名称，建议使用emp端的主键名称 -->
		<id name="cardId" column="emp_no">
			<!-- 使用外键的方式来生成主键 -->
			<generator class="foreign">
				<!-- 指定idCard这一端的emp属性 -->
				<param name="property">emp</param>
			</generator>
		</id>
		<property name="cardNo" column="card_no"></property>
		<!-- 
			指定一对一的关系
			name：当前端的的另一个一的一端的属性名称emp
			constrained：建表时带有外键约束
		 -->
		<one-to-one name="emp" constrained="true"></one-to-one>
	</class>	
</hibernate-mapping>

After you create the Hibernate mapping file you want to register to our hibernate.cfg.xml, and then export the database can be.

3, one single-ended test

Storage

public void testAdd()
{
	Session session = HibernateUtils.getSession();
	Transaction tx = session.beginTransaction();
	try
	{
		// 创建员工
		Emp emp = new Emp();
		emp.setEname("魏宇轩");
		emp.setAddress("昆明");
		emp.setGender(1);
		emp.setBirthday(new Date());
		// 创建身份证
		IDCard ic = new IDCard();
		ic.setCardNo("1234567890");
		// 指定一对一的关系
		ic.setEmp(emp);
		// 保存ic的时候自动的保存了emp，因为ic的主键是emp的主键，
		// 如果emp不保存主键就不会返回，所以在ic保存之前必须先保存emp
		session.save(ic);
		tx.commit();
	} catch (Exception e)
	{
		e.printStackTrace();
		tx.rollback();
	} finally
	{
		HibernateUtils.closeResource(session);
	}
}

Inquire

public void testQuery()
{
	Session session = HibernateUtils.getSession();
	try
	{
		IDCard card = (IDCard) session.get(IDCard.class, 1);
		System.out.println(card);
		System.out.println(card.getEmp());
	} catch (Exception e)
	{
		e.printStackTrace();
	} finally
	{
		HibernateUtils.closeResource(session);
	}
}

4, one to one mapping bidirectional associations

Emp modify the model, adding attributes idcard this end.

In the configuration of emp.hbm.xml

<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC
        "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
        "http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd">
<hibernate-mapping package="com.wyx.hiber.model">
	<class name="Emp" table="t_emp">
		<id name="empNo" column="emp_no">
			<generator class="native"></generator>
		</id>
		<property name="ename"></property>
		<property name="birthday"></property>
		<property name="gender"></property>
		<property name="address"></property>
		<!-- 
			双向关联映射的一对一，从数据库模型的箭头指向方向来看
			name：指定箭头背向端的model属性
		 -->
		<one-to-one name="card" cascade="save-update"></one-to-one>
	</class>
</hibernate-mapping>

Storage

public void testAdd()
{
	Session session = HibernateUtils.getSession();
	Transaction tx = session.beginTransaction();
	try
	{
		// 创建员工
		Emp emp = new Emp();
		emp.setEname("魏宇轩");
		emp.setAddress("昆明");
		emp.setGender(1);
		emp.setBirthday(new Date());
		// 创建身份证
		IDCard ic = new IDCard();
		ic.setCardNo("1234567890");
		// 设置员工和身份证的关系,由于是双向映射需要指定双向的关系
		emp.setCard(ic);
		ic.setEmp(emp);
		// 先保存emp
		session.save(emp);
		// 保存ic
		session.save(ic);
		tx.commit();
	} catch (Exception e)
	{
		e.printStackTrace();
		tx.rollback();
	} finally
	{
		HibernateUtils.closeResource(session);
	}
}

Use cascade would not have saved a single ic

Inquire

public void testQuery()
{
	Session session = HibernateUtils.getSession();
	try
	{
		Emp emp = (Emp) session.get(Emp.class, 1);
		System.out.println(emp);
		System.out.println(emp.getCard());
	} catch (Exception e)
	{
		e.printStackTrace();
	} finally
	{
		HibernateUtils.closeResource(session);
	}
}

From the direction of the arrow pointing to the query using the join query

If wrong, please correct me!