组件在Hibernate中作为复合标识符 [英] Components as composite identifiers in Hibernate

问题描述

我遵循 Hibernate文档并试图实现 9.4部分的示例。组件作为复合标识符但面临着如何实现它的问题。

以下是我所做的：

我的实体类：

Order.java

  public class Order {
 private int id; 
私人套餐< OrderLine> lines = new HashSet< OrderLine>（）; 
 // Setters& Getters 
 
  

OrderLine.java

  public class OrderLine {
 private OrderLineId id; 
私人字符串名称; 
私人订单; 
 // Setters& Getters 
 
  

OrderLineId.java

  public class OrderLineId implements Serializable {
 private int lineId; 
 private int orderId; 
 private int customerId; 
 // Setters& Getters 
} 
  

我的映射文件存在问题：

 < hibernate-mapping> 
< class name =Ordertable =TEST_Order> 
< id name =idtype =intcolumn =id> 
< generator class =native/> 
< / id> 
< set name =linescascade =all> 
< key column =orderId/> 
<一对多等级=OrderLine/> 
< / set> 
< / class> 
 
< class name =OrderLinetable =TEST_OrderLine> 
< composite-id name =idclass =OrderLineId> 
< key-property name =lineId/> 
< key-property name =orderId/> 
< key-property name =customerId/> 
< / composite-id> 
 
< property name =name/> 
 
<多对一名称=orderclass =Order
 insert =falseupdate =false> 
< column name =orderId/> 
< column name =customerId/> 
< /多对一> 
< / class> 
< / hibernate-mapping> 
  

当我试图创建解析这个映射文件的会话工厂时，我得到一个异常：

 引起：org.hibernate.MappingException：外键（FK_89b4nqt5l2n6tfd1d5tq0ill0：TEST_OrderLine [orderId，customerId]））必须相同作为引用主键的列数（TEST_Order [id]）
在org.hibernate.mapping.ForeignKey.alignColumns（ForeignKey.java:110）
在org.hibernate.mapping.ForeignKey.alignColumns（ ForeignKey.java:93）
 at org.hibernate.cfg.Configuration.secondPassCompileForeignKeys（Configuration.java:1816）
 at org.hibernate.cfg.Configuration.originalSecondPassCompile（Configuration.java:1739）
 at org.hibernate.cfg.Configuration.secondPassCompile（Configuration.java:1424）
 at org.hibernate.cfg.Configuration.buildSessionFactory（Configuration.java:1844）
  

有人可以帮助我如何实现给出的示例

解决方案

OrderLine需要引用Order PK，它不是一个复合键。
$ b

这意味着多对一必须是：

 < many-to- one name =orderclass =Order
 insert =falseupdate =false> 
< column name =orderId/> 
< /多对一> 
  

orderId是Order.id的FK。

然后一对多一方将变成：

 < set name =linescascade =所有> 
< key> 
< column name =orderId/> 
< / key> 
<一对多等级=OrderLine/> 
< / set> 
  

所以即使OrderLine有一个组合键，引用也是在Order.id之后进行的，是一个简单的键。

如果要将其他关联映射到OrderLine，如OrderLineProduct，则需要使用复合关键字来映射父关联（OrderLine）和子级（OrderLineProduct），以便OrderLineProduct将组合外键返回给OrderLine。

I am following Hibernate Documentation and trying to implement the example given for section 9.4. Components as composite identifiers but facing issues on how to implement it.

Here is what I have done:

My entity classes:

Order.java

public class Order {
    private int id;
    private Set<OrderLine> lines = new HashSet<OrderLine>();
   // Setters & Getters
}

OrderLine.java

public class OrderLine {
    private OrderLineId id;
    private String name;
    private Order order;
   // Setters & Getters
}

OrderLineId.java

public class OrderLineId implements Serializable{
    private int lineId;
    private int orderId;
    private int customerId;
   // Setters & Getters
}

My mapping file which is having issues:

<hibernate-mapping>
   <class name="Order" table="TEST_Order">
      <id name="id" type="int" column="id">
         <generator class="native"/>
      </id>
      <set name="lines" cascade="all">
         <key column="orderId"/>
         <one-to-many class="OrderLine"/>
      </set>
   </class>

<class name="OrderLine" table="TEST_OrderLine">
    <composite-id name="id" class="OrderLineId">
        <key-property name="lineId"/>
        <key-property name="orderId"/>
        <key-property name="customerId"/>
    </composite-id>

    <property name="name"/>

    <many-to-one name="order" class="Order"
            insert="false" update="false">
        <column name="orderId"/>
        <column name="customerId"/>
    </many-to-one>
</class>
</hibernate-mapping>

When I am trying to create a session factory which parses this mapping file, I am getting an exception saying:

Caused by: org.hibernate.MappingException: Foreign key (FK_89b4nqt5l2n6tfd1d5tq0ill0:TEST_OrderLine [orderId,customerId])) must have same number of columns as the referenced primary key (TEST_Order [id])
    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:1816)
    at org.hibernate.cfg.Configuration.originalSecondPassCompile(Configuration.java:1739)
    at org.hibernate.cfg.Configuration.secondPassCompile(Configuration.java:1424)
    at org.hibernate.cfg.Configuration.buildSessionFactory(Configuration.java:1844)

Can someone please help me how to implement the example given in the documentation.

解决方案

The OrderLine needs to refernece the Order PK, which is not a composite key.

It means the many-to-one must be:

<many-to-one name="order" class="Order"
        insert="false" update="false">
    <column name="orderId"/>
</many-to-one>

The orderId is the FK to Order.id.

Then the one-to-many side will become:

<set name="lines" cascade="all">
    <key>
        <column name="orderId"/>
    </key>
    <one-to-many class="OrderLine"/>
</set>

So even if the OrderLine has a composite-key, the reference is made after Order.id, which is a simple key.

If you want to map other association to OrderLine, like OrderLineProduct then you'll need to use the composite-key to map the association between the parent (OrderLine) and the child (OrderLineProduct), so that OrderLineProduct has a composite-foreign-key back to OrderLine.

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