多到多hibernate xml配置

Question

我有这样的DB关系。

​

我想要多到多的关系。在PLAYER和PRIVILEGE之间。你能帮我修复我的.xml吐露吗？

预期结果：我希望能够执行：String hql = "from Player as p right outer join p.privilages as priv";

实战:到目前为止我得到的是：：

org.hibernate.MappingException:外键(FK8CD18EE134F64423:PLAYER ID )必须具有与引用的主键相同的列数(特权ID、特权)

<hibernate-mapping>
    <class name="model.Privilage" table="PRIVILAGE">
        <id name="id" type="int" >
            <column name="ID"  precision="5" scale="0"/>
            <generator class="increment"/>
        </id>

        <set name="players" table="PLAYER"
             inverse="false" lazy="true" fetch="select" cascade="all" >
            <key>
                <column name="ID"/>
            </key>
            <many-to-many entity-name="model.Player">
                <column name="ID" not-null="true" />
            </many-to-many>
        </set>

        <property name="privilage" type="string">
            <column name="PRIVILAGE" length="20" not-null="true" />
        </property>
    </class>
</hibernate-mapping>

和

<class name="model.Player" table="PLAYER">
    <id name="playerId" type="int" >
        <column name="ID" precision="5" scale="0"/>
        <generator class="sequence">
            <param name="sequence">PLAYER_SEQ</param>
        </generator>
    </id>
    <set name="privilages" table="PRIVILAGE"
         inverse="false" lazy="true" fetch="select" cascade="all" >
        <key>
            <column name="ID"/>
        </key>
        <many-to-many entity-name="model.Privilage">
            <column name="PRIVILAGE" not-null="true" />
        </many-to-many>
    </set>
    <!-- ... -->
</class>

​

Answer 1

您应该引用名为PLAYER_PRIV的多到多关系表：

<set name="privilages" table="PLAYER_PRIV"
     inverse="true" lazy="true" fetch="select">
    <key>
        <column name="ID"/>
    </key>
    <many-to-many entity-name="model.Privilage">
        <column name="PRIV_ID" not-null="true"/>
    </many-to-many>
</set>

和

<set name="players" table="PLAYER_PRIV"
     inverse="false" lazy="true" fetch="select">
    <key>
        <column name="ID"/>
    </key>
    <many-to-many entity-name="model.Player">
        <column name="PLAYER_ID" not-null="true"/>
    </many-to-many>
</set>

Answer 2

您正在映射错误的关联表名称及其列。

1)双方的关联表相同(PLAYER_PRIV)：

<set name="privilages" table="PLAYER_PRIV"
    ...
</set>

<set name="players" table="PLAYER_PRIV"
    ...
</set>

2) Privilage映射中的列：

<key>
   <column name="PRIV_ID"/>
</key>
<many-to-many entity-name="model.Player">
   <column name="PLAYER_ID" not-null="true" />
</many-to-many>

在Player映射中，情况正好相反：

<key>
   <column name="PLAYER_ID"/>
</key>
<many-to-many entity-name="model.Privilage">
   <column name="PRIV_ID" not-null="true" />
</many-to-many>

3)除此之外，你必须选择一边成为inverse。来自文档

如果关联是双向的，则一方必须是所有者，一方必须是反向的(即。在更新关联表中的关系值时，它将被忽略)。

4)您可能不希望在多到多的关联中使用cascade=all，因为在删除特权时，您可能不希望删除授予特权的所有参与者。