hibernate一对一主键唯一外键关联（一）

来源：互联网发布：查分软件编辑：程序博客网时间：2024/05/01 00:20

1.新建工程项目hibernate_one2one_ufk_1,添加hibernate所需Jar包和数据库驱动Jar包。

2.编写工具类HibernateUtils.java和ExportDB.java,代码如下：

HibernateUtils.java

package com.i51pro.hibernate;
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.cfg.Configuration;
public class HibernateUtils {
    private static SessionFactory sessionFactory;
    static {
        try {
            Configuration cfg = new Configuration().configure();
            sessionFactory = cfg.buildSessionFactory();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
    public static SessionFactory getSessionFactory() {
        return sessionFactory;
    }
    public static Session getSession() {
        return sessionFactory.openSession();
    }
    public static void closeSession(Session session) {
        if (session != null) {
            if (session.isOpen()) {
                session.close();
            }
        }
    }
}

ExportDB.java

package com.i51pro.hibernate;
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.cfg.Configuration;
public class HibernateUtils {
    private static SessionFactory sessionFactory;
    static {
        try {
            Configuration cfg = new Configuration().configure();
            sessionFactory = cfg.buildSessionFactory();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
    public static SessionFactory getSessionFactory() {
        return sessionFactory;
    }
    public static Session getSession() {
        return sessionFactory.openSession();
    }
    public static void closeSession(Session session) {
        if (session != null) {
            if (session.isOpen()) {
                session.close();
            }
        }
    }
}

3.编写实体类和映射文件，代码如下：

IdCard.java

package com.i51pro.hibernate;
public class IdCard {
    private int id;
    
    private String cardNo;
    public int getId() {
        return id;
    }
    public void setId(int id) {
        this.id = id;
    }
    public String getCardNo() {
        return cardNo;
    }
    public void setCardNo(String cardNo) {
        this.cardNo = cardNo;
    }
}

Person.java

package com.i51pro.hibernate;
public class Person {
    private int id;
    
    private String name;
    private IdCard idCard;
    
    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 IdCard getIdCard() {
        return idCard;
    }
    public void setIdCard(IdCard idCard) {
        this.idCard = idCard;
    }
}

IdCard.hbm.xml

<?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="com.i51pro.hibernate.IdCard" table="t_idcard">
        <id name="id">
            <generator class="native"/>
        </id>
        <property name="cardNo"/>
    </class>
</hibernate-mapping>

Person.hbm.xml

<?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="com.i51pro.hibernate.Person" table="t_person">
        <id name="id">
            <generator class="native" />
        </id>
        <property name="name"/>
        <many-to-one name="idCard" unique="true" />
    </class>
</hibernate-mapping>

4.编写hibernate映射文件，代码如下：

hibernate.cfg.xml

<!DOCTYPE hibernate-configuration PUBLIC
    "-//Hibernate/Hibernate Configuration DTD 3.0//EN"
    "http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd">
<hibernate-configuration>
    <session-factory>
        <property name="hibernate.connection.url">jdbc:mysql://localhost/hibernate_one2one_ufk_1</property> 
        <property name="hibernate.connection.driver_class">com.mysql.jdbc.Driver</property>
        <property name="hibernate.connection.username">root</property>
        <property name="hibernate.connection.password">admin</property>
        <property name="hibernate.dialect">org.hibernate.dialect.MySQLDialect</property>
        <property name="hibernate.show_sql">true</property>
        
        <mapping resource="com/i51pro/hibernate/Person.hbm.xml"/>
        <mapping resource="com/i51pro/hibernate/IdCard.hbm.xml"/>
    </session-factory>
</hibernate-configuration>

5.在工程项目下新建SourceFolder,命名为test,在该包下编写单元测试类One2OneTest.java,进行单元测试，它的代码如下：

One2OneTest.java

package com.i51pro.hibernate;
import org.hibernate.Session;
import org.hibernate.Transaction;
import junit.framework.TestCase;
public class One2OneTest extends TestCase {
    public void testSave1() {
        Session session = null;
        try {
            session = HibernateUtils.getSession();
            Transaction tx = session.beginTransaction();
            
            IdCard idCard = new IdCard();
            idCard.setCardNo("88888888");
            
            Person person = new Person();
            person.setName("李小晚");
            person.setIdCard(idCard);
            
            //不能保存，因为idCard是Transident状态 
            session.save(person);
            
            session.getTransaction().commit();
        }catch(Exception e) {
            e.printStackTrace();
            session.getTransaction().rollback();
        }finally {
            HibernateUtils.closeSession(session);
        }
    }   
        public void testSave2() {
            Session session = null;
            try {
                session = HibernateUtils.getSession();
                Transaction tx = session.beginTransaction();
                
                IdCard idCard = new IdCard();
                idCard.setCardNo("88888888");
                session.save(idCard);
                
                Person person = new Person();
                person.setName("李小晚");
                person.setIdCard(idCard);
                
                session.save(person);
                
                session.getTransaction().commit();
            }catch(Exception e) {
                e.printStackTrace();
                session.getTransaction().rollback();
            }finally {
                HibernateUtils.closeSession(session);
            }
    }
    
    public void testLoad1() {
        Session session = null;
        try {
            session = HibernateUtils.getSession();
            Transaction tx = session.beginTransaction();
            
            Person person = (Person)session.load(Person.class, 2);
            System.out.println("person.name:" + person.getName() );
            System.out.println("idCard.name:" + person.getIdCard().getCardNo());
            
            session.getTransaction().commit();
        }catch(Exception e) {
            e.printStackTrace();
            session.getTransaction().rollback();
        }
    }
}

总结：hibernate一对一唯一外键关联映射（单向关联Person---->IdCard）

一对唯一外键关联映射是多对一关联映射的特例

可以采用<many-to-one>标签，指定多的一端的unique=true，这样就限制了多的一端的多重性为一
通过这种手段映射一对一唯一外键关联