Hibernate(六)多表联查之单向一对一

单向之一对一

举例：公民和身份证，一个公民对应一张身份证

1、工具类：HibernateUtil

public class HibernateUtilEX {
    private static Configuration configuration = null;
    private static SessionFactory sessionFactory = null;
    // 本地化线程、
    private static ThreadLocal<Session> localSession = null;

    static {
        try {
            // 加载Hibernate配置文件(默认加载bihernate.cfg.xml)
            configuration = new Configuration().configure();
            // 获取SessionFactory工厂对象
            sessionFactory = configuration.buildSessionFactory();

            localSession = new ThreadLocal<Session>();
        } catch (Exception e) {
            System.out.println("加载hibernate映射文件失败");
            e.printStackTrace();
        }
    }

    /**
     * 得到Session对象
     * 
     * @return Session
     */
    public static Session openSession() throws HibernateException {
        // 底层有一个Map<k,V>,K:线程ID，V:session ,一个线程绑定一个session
        Session session = localSession.get();
        if (session == null) {
            session = sessionFactory.openSession();
            localSession.set(session);
        }
        return session;
    }

    /**
     * 关闭Session
     * 
     * @throws HibernateException
     */
    public static void closeSession() throws HibernateException {
        Session session = localSession.get();
        if (session != null) {
            session.close();
        }
        localSession.set(null);
    }
}

2、公民实体类：CitizenEntity

public class CitizenEntity {
    private int id;
    private String name;
    private int age;
    public int getId() {
        return id;
    }
    public void setId(int id) {
        this.id = id;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public int getAge() {
        return age;
    }
    public void setAge(int age) {
        this.age = age;
    }
    @Override
    public String toString() {
        return "CitizenEntity [id=" + id + ", name=" + name + ", age=" + age + "]";
    }
}

配置文件：CitizenEntity

<?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 package="com.zh.entity">
    <class name="CitizenEntity" table="t_citizen">
        <!-- 映射标识属性(属性) -->
        <id name="id" column="citizen_id" type="int">
            <!-- 主键生成策略(自增主键) -->
            <generator class="native" />
        </id>

        <!-- 映射普通属性 -->
        <property name="name" column="name"></property>
        <property name="age" column="age"></property>
    </class>
</hibernate-mapping>

省份证实体类：IdCardEntity.hbm.xml

public class IdCardEntity {
    private int id;
    private String sn; //编号
    private int validDate;  //有效期
    private CitizenEntity citizen;  //公民
    public int getId() {
        return id;
    }
    public void setId(int id) {
        this.id = id;
    }
    public String getSn() {
        return sn;
    }
    public void setSn(String sn) {
        this.sn = sn;
    }
    public int getValidDate() {
        return validDate;
    }
    public void setValidDate(int validDate) {
        this.validDate = validDate;
    }
    public CitizenEntity getCitizen() {
        return citizen;
    }
    public void setCitizen(CitizenEntity citizen) {
        this.citizen = citizen;
    }
    @Override
    public String toString() {
        return "IdCardEntity [id=" + id + ", sn=" + sn + ", validDate=" + validDate + ", citizen=" + citizen + "]";
    }
}

配置文件：IdCardEntity.hbm.xml

<?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 package="com.zh.entity">
    <class name="IdCardEntity" table="t_IDCard">
        <!-- 映射标识属性(属性) -->
        <id name="id" column="id" type="int">
            <!-- 主键生成策略(自增主键) -->
            <generator class="native" />
        </id>

        <!-- 映射普通属性 -->
        <property name="sn" column="sn"></property>
        <property name="validDate" column="validDate"></property>
        <!-- unique="true" 设置唯一约束 -->
        <many-to-one name="citizen" class="CitizenEntity"  column="citizen_id" unique="true"></many-to-one>
    </class>
</hibernate-mapping>

3、在总配置文件hibernate.cfg.xml里添加配置映射文件

4、创建测试类：HibernateTest**

public class HibernateTest {
    public static void main(String[] args) {
        HibernateTest test=new HibernateTest();
        test.singleOneToOne();
    }
    //单向一对一测试
        public void singleOneToOne() {
            //开启会话
            Session session=HibernatUtil.getSession();
            //打开事物
            Transaction transaction=session.beginTransaction();
            /**
             * 创建公民实体
             */
            CitizenEntity citizenEntity=new CitizenEntity();
            citizenEntity.setName("王五");
            citizenEntity.setAge(22);
            session.persist(citizenEntity);
            /**
             * 创建身份证实体
             */
            IdCardEntity cardEntity=new IdCardEntity();
            cardEntity.setSn("511025199900006789");
            cardEntity.setValidDate(20);

            cardEntity.setCitizen(citizenEntity);
            //保存到数据库
            session.persist(cardEntity);
            //事物提交
            transaction.commit();
            //关闭会话
            HibernatUtil.closeSession(session);
        }
}

创建完成！