一对一关系

表与表之间互相对应，各式互相的唯一
常用的例子是：身份证和人之间的关系，或是工作证与个人的关系，我这里举例老师和工作证的关系。

teachers表

字段名	类型	约束
id	int	主键
t_name	varchar

card表

字段名	类型	约束
card_num	varchar
t_id	int	主键/外键

Teachers.java

package com.ben.pojo;

import java.io.Serializable;
import java.util.HashSet;
import java.util.Set;

public class Teachers implements Serializable {

    private Integer id;
    private String tName;
    //card对象
    private Card card;

    public Integer getId() {
        return id;
    }

    public void setId(Integer id) {
        this.id = id;
    }

    public String gettName() {
        return tName;
    }

    public void settName(String tName) {
        this.tName = tName;
    }

    public Card getCard() {
        return card;
    }

    public void setCard(Card card) {
        this.card = card;
    }

    public Teachers() {
        super();
    }

    public Teachers(String tName) {
        super();
        this.tName = tName;
    }

}

Card.java

注意：一个tId设置为主键；一个teacher设置为外键的对象。
即——主键表因为主外键都是一个字段，所以在域对象设定的时候要设置主键和外键。

package com.ben.pojo;

import java.io.Serializable;

public class Card implements Serializable {

    private Integer tId;
    private Teachers teacher;
    private String cardNum;

    public Integer gettId() {
        return tId;
    }

    public void settId(Integer tId) {
        this.tId = tId;
    }

    public Teachers getTeacher() {
        return teacher;
    }

    public void setTeacher(Teachers teacher) {
        this.teacher = teacher;
    }

    public String getCardNum() {
        return cardNum;
    }

    public void setCardNum(String cardNum) {
        this.cardNum = cardNum;
    }

    public Card() {
        super();
    }

    public Card(Teachers teacher, String cardNum) {
        super();
        this.teacher = teacher;
        this.cardNum = cardNum;
    }

}

Teachers.hbm.xml

注意：外键表，要设置级联关系

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-mapping PUBLIC
    "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
    "http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd">
<hibernate-mapping>
    <class name="com.ben.pojo.Teachers" table="teachers">
        <id name="id" column="id" type="java.lang.Integer">
            <generator class="native"></generator>
        </id>
        <property name="tName" type="java.lang.String">
            <column name="t_name"></column>
        </property>

        <!-- <set name="grades" cascade="save-update">
            <key column="gid"></key>
            <many-to-many></many-to-many>
        </set> -->

        <!-- 一对一,外键表配置级联关系 -->
        <one-to-one name="card" class="com.ben.pojo.Card" cascade="all"></one-to-one>

    </class>
</hibernate-mapping>

Card.hbm.xml

注意：这里主键的生成方式为'foreign'。
<param name="property"></param>中间的参数与下文配置的name相同

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-mapping PUBLIC
    "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
    "http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd">
<hibernate-mapping>
    <class name="com.ben.pojo.Card" table="card">
        <id name="tId" column="t_id" type="java.lang.Integer">
            <generator class="foreign">
                <param name="property">teacher</param>
            </generator>
        </id>
        <property name="cardNum" type="java.lang.String">
            <column name="card_num"></column>
        </property>

        <!-- 一对一 -->
        <one-to-one name="teacher" class="com.ben.pojo.Teachers"></one-to-one>

    </class>
</hibernate-mapping>

测试用例

@Test
public void test() {
    Session session = MySessionFactory.getSession();
    Transaction tx = session.beginTransaction();

    Teachers t = new Teachers("laoshi2");
    Card c = new Card(t, "11223344556688");
    t.setCard(c);
    session.save(t);

    tx.commit();
}

注意，在创建Teachers对象后，不要忘记设置Card，否则保存Teachers对象会不保存Card的。但是这时保存Card会保存Teachers对象，自己要理好关系。

Hibernate:
    insert
    into
        teachers
        (t_name)
    values
        (?)
Hibernate:
    insert
    into
        card
        (card_num, t_id)
    values
        (?, ?)