Question

我在设置OneToMany关系方面遇到了问题。

我的数据库架构：

TABLE PARENT (
VENDOR,
CHANNEL,
CREATEDATE,
REFID,
...
)
UNIQUE INDEX PK_PARENT (VENDOR, CHANNEL, CREATEDATE, REFID)

TABLE CHILD (
REFID,
NAME,
)
UNIQUE INDEX PK_CHILD (REFID, NAME)

和Java类

public class Parent {
    String vendor;
    String channel;
    Date createdate;
    Long refid;
    List<Child> childs;
    ...
}

public class Child {
    Long refid;
    String name;
}

我的问题是我无法为这些类开发正确的映射。出于一致的原因，我被迫使用hbm xml。我能够将它映射为两个独立的实体。

<hibernate-mapping>
<class name="Parent" table="PARENT">
    <composite-id >
        <key-property name="vendor" type="string">
            <column name="VENDOR" />
        </key-property>
        <key-property name="vendor" type="string">
            <column name="CHANNEL" />
        </key-property>
        <key-property name="vendor" type="Date">
            <column name="CREATEDATE" />
        </key-property>
        <key-property name="vendor" type="Long">
            <column name="REFID" />
        </key-property>
    <composite-id />
    <list name="childs" table="CHILD" lazy="true" fetch="select">
        <key column="REFID" />
        <index column="REFID" />
        <one-to-many class="Child" />
    </list>
</class>

<class name="Child" table="CHILD">
    <composite-id >
        <key-property name="vendor" type="Long">
            <column name="REFID" />
        </key-property>
        <key-property name="name" type="string">
            <column name="NAME" />
        </key-property>
    <composite-id />
</class>
</hibernate-mapping>

我得到例外：

Caused by: org.hibernate.MappingException: Foreign key (FK_9897tr114hxkewktsi9vb92x6:CHILD[REFID])) must have same number of columns as the referenced primary key (PARENT[VENDOR,CHANNEL,CREATEDATE,REFID]) 
at org.hibernate.mapping.ForeignKey.alignColumns(ForeignKey.java:110)
    at org.hibernate.mapping.ForeignKey.alignColumns(ForeignKey.java:93)
    at org.hibernate.cfg.Configuration.secondPassCompileForeignKeys(Configuration.java:1818)
    at org.hibernate.cfg.Configuration.originalSecondPassCompile(Configuration.java:1741)
    at org.hibernate.cfg.Configuration.secondPassCompile(Configuration.java:1426)
    at org.hibernate.cfg.Configuration.buildSessionFactory(Configuration.java:1846)
    at org.hibernate.cfg.Configuration.buildSessionFactory(Configuration.java:1930)

对此有何看法？

Answer 1

因为您的Child实体具有复杂的键，因此在Parent实体中您还需要将外键指定为复数。

Answer 2

根据hibernate配置xml文件中的java类字段更改属性名称。如果您的java类中有“channel”字段，那么它应该在您的hbm配置中命名为“channel”，尽管它是复合主键的一部分。

<class name="Parent" table="PARENT">
<composite-id >
    <key-property name="vendor" type="string">
        <column name="VENDOR" />
    </key-property>
    <key-property name="channel" type="string">
        <column name="CHANNEL" />
    </key-property>
    <key-property name="createdate" type="Date">
        <column name="CREATEDATE" />
    </key-property>
    <key-property name="refid" type="Long">
        <column name="REFID" />
    </key-property>
<composite-id />
<list name="childs" table="CHILD" lazy="true" fetch="select">
    <key column="REFID" />
    <index column="REFID" />
    <one-to-many class="Child" />
</list>

此外，您应该在映射的另一侧定义manyToOne关系。并且子类中可以有一个Parent实例。（不仅仅是一个ID）

Hibernate OneToMany，自然PK

2 个答案: