父/子关系与休眠问题 [英] Problem with parent/child relation with hibernate

问题描述

我正面临父子类型关系的问题。

Hibernate文档说在子类中添加一个多对一关系以从父类获取外键的值。但为了使这种关系起作用，我必须在子类中添加Invoice属性，将父项的循环包含到子元素中并打破我的序列化程序。有人能指出我在哪里做错了吗？

以下是我的代码：

Invoice.java

  public class Invoice implements Serializable {
 private Long id; 
私人日期invDate; 
私人字符串客户; 
 private Set< InvoiceItem>项目; 
 ... getters / setters ... 
} 
  

InvoiceItem.java

  public class InvoiceItem实现Serializable {
 private Long itemId; 
私人长期产品ID; 
 private int数量; 
私人双重价格; 
私人发票发票; // ??????? 
 ... getters / setters ... 
} 
  

Invoice.hbm .xml

 < class name =Invoicetable =Invoices> 
< id name =idcolumn =IDtype =long> 
< generator class =native/> 
< / id> 
< property name =invDatetype =timestamp/> 
< property name =customertype =string/> 
 
< set name =itemsinverse =truecascade =all-delete-orphan> 
< key column =invoiceId/> 
 < / set> 
< / class> 
  

InvoiceItem.hbm.xml

 < class name =InvoiceItemtable =InvoiceItems> 
< id name =itemIdtype =longcolumn =id> 
< generator class =native/> 
< / id> 
 
< property name =productIdtype =long/> 
< property name =quantitytype =int/> 
< property name =pricetype =double/> 
 
 < / class> 
  

解决方案

您不必对发票在InvoiceItem中，如果你删除了inverse =true属性。
然后，Hibernate将创建一个单独的映射表，而不是在InvoiceItem表中使用外键。

移除 inverse 属性，并从映射中删除InvoiceItem中的Invoice属性和相应的多对一，你应该得到你想要的。另外，您可以将InvoiceItem中的Invoice引用标记为transient，并在反序列化过程中处理填充值：遍历发票中的Set of Items项，并设置 code>发票将每件物品的财产归入所有权发票。

I am facing a problem with parent child type relations.
Hibernate docs say to add a "many-to-one" relation in child class to get value of foreign key from parent. But to make this relation work I have to add Invoice property in child class that introduce a circular inclusion of parent into child and breaks my serializer. Could somebody point where am I doing mistake?

Here is my code:

Invoice.java

public class Invoice implements Serializable {
  private Long id;
  private Date invDate;
  private String customer;
  private Set<InvoiceItem> items;
  ... getters/setters ...
}

InvoiceItem.java

public class InvoiceItem implements Serializable {
  private Long itemId;
  private long productId;
  private int quantity;
  private double price;
  private Invoice invoice; //???????
  ... getters/setters ...
}

Invoice.hbm.xml

<class name="Invoice" table="Invoices">
  <id name="id" column="ID" type="long">
    <generator class="native" />
  </id>
  <property name="invDate" type="timestamp" />
  <property name="customer" type="string" />

  <set name="items" inverse="true" cascade="all-delete-orphan">
    <key column="invoiceId" />
    <one-to-many class="InvoiceItem" />
  </set>
</class>

InvoiceItem.hbm.xml

<class name="InvoiceItem" table="InvoiceItems">
  <id name="itemId" type="long" column="id">
    <generator class="native" />
  </id>

  <property name="productId" type="long" />
  <property name="quantity" type="int" />
  <property name="price" type="double" />

<many-to-one name="invoiceId" class="Invoice" not-null="true"/> <!--????????-->
</class>

解决方案

You don't have to have a reference to Invoice in InvoiceItem if you remove the inverse="true" attribute. Hibernate will then create a separate mapping table rather than use a foreign key in the InvoiceItem table.

Remove the inverse attribute on the InvoiceItem set, and also remove the Invoice property from InvoiceItem, and the corresponding many-to-one in the mapping and you should get what you want.

Alternatively, you could mark the Invoice reference in InvoiceItem as transient, and handle populating the value during deserialization: iterate over the Set of Items in Invoice, and set the invoice property on each item to the owning invoice.

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