java - hibernate 对不同的列使用两个外键？

Question

是否可以映射链接到同一个表的两个外键？我最好向你展示我的意思。

我有一个名为 fixtures 的表，目前看起来像这样:

<class name="" table="">
    <id name="id" column="id">
        <generator class="Increment" />
    </id>
    <property name="date" type="" column="" />
    <property name="" type="" column="" />
    <many-to-one name="awayTeam" column="teamId" not-null="true" />
    <many-to-one name="homeTeam" column="teamId" not-null="true" />
</class>

我还有另一个名为 Teams 的表，其中包含团队数据。

<class name="" table="">
    <id name="teamId" column="id">
        <generator class="Increment" />
    </id>
    <property name="name" type="String" column="name" />
    <property name="fixturesUrl" type="String" column="fixturesUrl" />
    <property name="rssNewsUrl" type="String" column="rssNewsUrl" />
</class>

在一场比赛/比赛中，每场比赛都有两支球队，一支客场球队和一支主场球队，我希望它能够映射并与我的球队表建立一对多关系。这在 hibernate 中可能吗？如果是这样，如何？我的代码中缺少什么？

他们是否也表示每个赛程记录不能让相同的球队互相比赛，即客场和主队必须是唯一的？

提前加油

Answer 1

is it possible to map two foreign keys linked to the same table?

是的。你有什么应该工作。如果不是，请说明问题。

Is their also a way to say each fixture record cannot have same teams playing eachother i.e. away and home team has to be unique?

使用 properties 应该是可行的元素。来自文档:

5.1.16. Properties

The <properties> element allows the definition of a named, logical grouping of the properties of a class. The most important use of the construct is that it allows a combination of properties to be the target of a property-ref. It is also a convenient way to define a multi-column unique constraint.

另见 previous question了解更多详情。

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更新:我不确定为什么，但我无法获得使用 <properties> 生成的唯一 key 元素(也许我误用了它，我没有尝试太久)但这是一个使用 <natural-id> 的解决方案元素。

团队映射:

<?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.stackoverflow.q4089539.Team" table="TEAM">
    <id name="id" type="java.lang.Long">
      <column name="ID" />
      <generator class="native" />
    </id>
    <property name="name" type="java.lang.String">
      <column name="NAME" />
    </property>
    <property name="fixturesUrl" type="java.lang.String">
      <column name="FIXTURESURL" />
    </property>
    <property name="rssNewsUrl" type="java.lang.String">
      <column name="RSSNEWSURL" />
    </property>
  </class>
</hibernate-mapping>

和夹具:

<?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.stackoverflow.q4089539.Fixture" table="FIXTURE">
    <id name="id" type="java.lang.Long">
      <column name="ID" />
      <generator class="native" />
    </id>
    <natural-id mutable="false">
      <many-to-one class="com.stackoverflow.q4089539.Team" name="awayTeam" not-null="true">
        <column name="AWAYTEAM"/>
      </many-to-one>
      <many-to-one class="com.stackoverflow.q4089539.Team" name="homeTeam" not-null="true">
        <column name="HOMETEAM" />
      </many-to-one>
    </natural-id>
    <property generated="never" lazy="false" name="date" type="java.util.Date">
      <column name="DATE" />
    </property>
  </class>
</hibernate-mapping>

这是生成的 DDL:

create table FIXTURE (
    ID bigint not null,
    AWAYTEAM bigint not null,
    HOMETEAM bigint not null,
    DATE timestamp,
    primary key (ID),
    unique (AWAYTEAM, HOMETEAM)
)

create table TEAM (
    ID bigint not null,
    NAME varchar(255),
    FIXTURESURL varchar(255),
    RSSNEWSURL varchar(255),
    primary key (ID)
)

alter table FIXTURE 
    add constraint FKF88585E9445D9A98 
    foreign key (AWAYTEAM) 
    references TEAM

alter table FIXTURE 
    add constraint FKF88585E987B44C09 
    foreign key (HOMETEAM) 
    references TEAM