一对多 多对一 外键双向关联

一个皇帝对应多个大臣如下：

emperor_info did(int 4 pk )  name(varchar)

minister_info  mid(int 4 pk)  name(varchar)  did(int int 4 fk) 

 

实体：

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package bi.one2many;

 

import java.util.HashSet;

import java.util.Set;

 

public class Emperor {

    private int id;

    private String name;

    private Set<Minister> ministers = new HashSet<Minister>();

 

    public Emperor() {

 

    }

 

    public Emperor(int id, String name, Set<Minister> ministers) {

        super();

        this.id = id;

        this.name = name;

        this.ministers = ministers;

    }

 

    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 Set<Minister> getMinisters() {

        return ministers;

    }

 

    public void setMinisters(Set<Minister> ministers) {

        this.ministers = ministers;

    }

 

}

 

package bi.one2many;

 

public class Minister {

    private int id;

    private String name;

    private Emperor emperor;

 

    public Minister() {

 

    }

 

    public Minister(int id, String name, Emperor emperor) {

        super();

        this.id = id;

        this.name = name;

        this.emperor = emperor;

    }

 

    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 Emperor getEmperor() {

        return emperor;

    }

 

    public void setEmperor(Emperor emperor) {

        this.emperor = emperor;

    }

 

}

　　

hbm配置文件：

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<hibernate-mapping>

    <class name="bi.one2many.Emperor">

        <id name="id" column="did">

            <generator class="native" />

        </id>

        <property name="name" type="string" column="name"></property>

         

        <!-- confirure the uniredirection association -->

        <set name="ministers" inverse="true" cascade="all">

            <key column="did" not-null="true"></key>

            <one-to-many class="bi.one2many.Minister"/>

        </set>

    </class>

 

</hibernate-mapping>

<hibernate-mapping>

    <class name="bi.one2many.Minister">

        <id name="id" column="mid">

            <generator class="native" />

        </id>

        <property name="name" type="string" column="name"></property>

        <many-to-one name="emperor" column="did" cascade="all"></many-to-one>

    </class>

 

</hibernate-mapping>

　　

测试文件：

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public class Test {

     

    @org.junit.Test

    public void testAdd() {

        SessionFactory sf = HibernateUtil.getSessionFactory();

        Session session = sf.getCurrentSession();

        session.beginTransaction();

         

        Minister m1 = new Minister();

        m1.setName("廉颇");

         

        Minister m2 = new Minister();

        m2.setName("蔺相如");

         

        Emperor emperor = new Emperor();

        emperor.setName("齐威王");

        //emperor.getMinisters().add(m1);

        //session.save(emperor);

         

        m1.setEmperor(emperor);

        m2.setEmperor(emperor);

         

        session.save(m1);

        session.save(m2);

        session.beginTransaction().commit();

    }

}

　　

测试结果：

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Hibernate: insert into Emperor (name) values (?)

Hibernate: insert into Minister (name, did) values (?, ?)

Hibernate: insert into Minister (name, did) values (?, ?)

　　

在双向关联关系配置中有inverse属性和cascade属性比较让人迷糊，不过参看一下这个文章写得蛮清楚的： 

Hibernate中的Inverse和cascade属性配置

http://www.cnblogs.com/focusj/archive/2011/03/23/2057603.html。