[Hibernate] - one to one

两种不同方式的一对一映射关系：

---

1）配置文件：

hibernate.cfg.xml

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-configuration PUBLIC
        "-//Hibernate/Hibernate Configuration DTD 3.0//EN"
        "http://www.hibernate.org/dtd/hibernate-configuration-3.0.dtd">

<hibernate-configuration>

    <session-factory>

        <!-- Database connection settings -->
        <property name="connection.driver_class">com.mysql.jdbc.Driver</property>
        <property name="connection.url">jdbc:mysql://127.0.0.1/testdb</property>
        <property name="connection.username">root</property>
        <property name="connection.password"></property>

        <!-- JDBC connection pool (use the built-in) -->
        <property name="connection.pool_size">1</property>

        <!-- SQL dialect -->
        <property name="dialect">org.hibernate.dialect.MySQL5Dialect</property>

        <!-- Enable Hibernate's automatic session context management -->
        <property name="current_session_context_class">thread</property>

        <!-- Disable the second-level cache  -->
        <property name="cache.provider_class">org.hibernate.cache.internal.NoCacheProvider</property>

        <!-- Echo all executed SQL to stdout -->
        <property name="show_sql">true</property>

        <!-- Drop and re-create the database schema on startup -->
        <property name="hbm2ddl.auto">update</property>

        <mapping resource="com/my/hbm/Employer.hbm.xml"/>
        <mapping resource="com/my/hbm/Address.hbm.xml"/>
        <mapping resource="com/my/hbm/Detial.hbm.xml"/>

    </session-factory>

</hibernate-configuration>

Employer.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>
    <class name="com.my.bean.Employer" table="employer">
        <id name="id" type="long">
            <column name="id"></column>
            <generator class="native"></generator>
        </id>
        <property name="companyName" type="java.lang.String" length="100" column="company_name" not-null="true" />
        <property name="createTime" type="java.util.Date">
            <column name="create_time" not-null="true"/>
        </property>
        <one-to-one name="address"></one-to-one>
        <one-to-one name="detial" property-ref="employer"></one-to-one>
    </class>
</hibernate-mapping>

Address.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>
    <class name="com.my.bean.Address" table="address">
        <id name="id" type="long" column="id">
            <generator class="foreign">
                <param name="property">employer</param>
            </generator>
        </id>
        <property name="location" column="location" length="200" not-null="true" type="java.lang.String"></property>
        <one-to-one name="employer" constrained="true"></one-to-one>
    </class>
</hibernate-mapping>

Detial.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>
    <class name="com.my.bean.Detial" table="detial">
        <id name="id" type="long" column="id">
            <generator class="native"></generator>
        </id>
        <many-to-one name="employer" column="employer_id" unique="true"></many-to-one>
        <property name="info" column="info" type="java.lang.String" length="3000"></property>
    </class>
</hibernate-mapping>

2）Java bean:

package com.my.bean;

import java.util.Date;

public class Employer {

    private long id;
    private String companyName;
    private Date createTime;
    private Address address;
    private Detial detial;

    public long getId() {
        return id;
    }
    public void setId(long id) {
        this.id = id;
    }
    public String getCompanyName() {
        return companyName;
    }
    public void setCompanyName(String companyName) {
        this.companyName = companyName;
    }
    public Date getCreateTime() {
        return createTime;
    }
    public void setCreateTime(Date createTime) {
        this.createTime = createTime;
    }
    public Address getAddress() {
        return address;
    }
    public void setAddress(Address address) {
        this.address = address;
    }
    public Detial getDetial() {
        return detial;
    }
    public void setDetial(Detial detial) {
        this.detial = detial;
    }

}

package com.my.bean;

public class Address {

    private long id;
    private String location;
    private Employer employer;

    public long getId() {
        return id;
    }
    public void setId(long id) {
        this.id = id;
    }
    public String getLocation() {
        return location;
    }
    public void setLocation(String location) {
        this.location = location;
    }
    public Employer getEmployer() {
        return employer;
    }
    public void setEmployer(Employer employer) {
        this.employer = employer;
    }

}

package com.my.bean;

public class Detial {
    private long id;
    private String info;
    private Employer employer;

    public long getId() {
        return id;
    }
    public void setId(long id) {
        this.id = id;
    }
    public String getInfo() {
        return info;
    }
    public void setInfo(String info) {
        this.info = info;
    }
    public Employer getEmployer() {
        return employer;
    }
    public void setEmployer(Employer employer) {
        this.employer = employer;
    }
}

3）测试：

package com.my.init;

import java.util.Date;
import java.util.HashSet;
import java.util.List;
import java.util.Set;

import javax.xml.soap.Detail;

import org.hibernate.Query;
import org.hibernate.Session;
import org.hibernate.Transaction;

import com.my.bean.Address;
import com.my.bean.Detial;
import com.my.bean.Employer;
import com.my.bean.User;
import com.my.bean.UserAccount;
import com.my.dao.util.HibernateUtil;

public class Test {

    @SuppressWarnings("unchecked")
    public static void main(String[] args) {
        Session session = HibernateUtil.getSessionFactory().openSession();
        Transaction tx = session.beginTransaction();

        // new employer
        Employer employer = new Employer();
        employer.setCompanyName("my company");
        employer.setCreateTime(new Date());

        // new address
        Address address = new Address();
        address.setLocation("china");

        // new detail
        Detial detail = new Detial();
        detail.setInfo("info");

        // add relation
        employer.setAddress(address);
        employer.setDetial(detail);
        address.setEmployer(employer);
        detail.setEmployer(employer);

        session.save(employer);
        session.save(address);
        session.save(detail);

        // Get employer
        String hsqlSelect = "from Employer";
        Query query = session.createQuery(hsqlSelect);
        List<Employer> es = query.list();
        if(es != null && es.size() > 0){
            Employer e = es.get(0);
            System.out.println(e.getCompanyName());
            System.out.println(e.getDetial().getInfo());
        }

        tx.commit();
        session.close();
    }

}

---

关注点：

1）Employer.hbm.xml

<generator class="native"></generator>

这个generator的class="native"值有好几种，具体使用方法可参见：http://blog.csdn.net/ye1992/article/details/19632001

<one-to-one name="address"></one-to-one>
<one-to-one name="detial" property-ref="employer"></one-to-one>

这里有两个one-to-one，两种一对一的不同映射方式。

其中第二种one-to-one中有一个属性引用，对应的是在detial中的employer属性。

property-ref的使用说明可参见：http://blog.csdn.net/fengyuanfa/article/details/5096764

2）Address.hbm.xml

<id name="id" type="long" column="id">
    <generator class="foreign">
        <param name="property">employer</param>
    </generator>
</id>

这是声明一个外部键字段的一对一关系用法。

<one-to-one name="employer" constrained="true"></one-to-one>

这里这个contrained设为true是必需的。

3）Detial.hbm.xml

<many-to-one name="employer" column="employer_id" unique="true"></many-to-one>

这是一对一关系的另一种现实方式，使用的是many-to-one，但unique设为true是必需的。

这两种不同的一对一关系映射，参考资料：

http://blog.csdn.net/mr__fang/article/details/8592000

http://www.tutorialspoint.com/hibernate/hibernate_one_to_one_mapping.htm