Hibernate使用ID查询外键字段 [英] Hibernate query a foreign key field with ID

问题描述

例如，我有两个实体：员工和地址。在这些实体中，Employee有一个外键AddressID引用Address上的ID列。在Java域对象中，Hibernate用Address对象域很好地包装了伪造关键字整数字段。但是现在，我怎么能用某个AddressID查询Employee？

我试图创建一个表别名。这似乎工作，但它相当尴尬。

我也尝试过这样做：

 标准.add（restriction.eq（TheAddressObjectFieldName，123）; 
  

它有点时间但并不总是。我不确定这是正确的方式，但我一直希望它可以。

那么什么是正确的方式来查询外键列hibernate？

解决方案

Hibernate很好地包装了你所要包装的东西，所以假设你的 Employee 映射看起来像这样：

  @Entity 
 public class Employee {
 ... 
 @ManyToOne 
 @JoinColumn（name =address_id）
私人地址; 
 ... 
} 
  

和您的地址有一个 id code> property，你可以通过 address_id 来查询：



  session.createCriteria（Employee.class）
 .add（Restrictions.eq（a ddress.id，addressId））; 
  

为了基于 Address 属性进行查询，您必须创建别名或嵌套标准：

$ p $ session.createCriteria（Employee.class）
.createAlias（address， a）
.add（Restrictions.eq（a.postalCode，postalCode））;





For example, I have two entities: Employee and Address. Of these enitities, Employee has a foreign key AddressID references the ID column on Address. In the Java domain objects, Hibernate nicely wraps the forgein key integer field with a Address object field. But now, how could I query the Employee with a certain AddressID?

I have tried to create a table alias. That seems to work, but it is fairly awkward.

I had also tried to do something like this:

criteria.add(restriction.eq("TheAddressObjectFieldName", 123);

It works some time but not always. I am not sure this is the right way, but I was hoping it could all the time.

So what is the right way to query on a foreign key column in hibernate?

解决方案

Hibernate "nicely wraps" only what you tell it to wrap. So, assuming that your Employee mapping looks something like:

@Entity
public class Employee {
  ...
  @ManyToOne
  @JoinColumn(name="address_id")
  private Address address;
  ...
}

and your Address has an id property, you can query based on address_id via:

session.createCriteria(Employee.class)
 .add(Restrictions.eq("address.id", addressId));

In order to query based on Address properties, you'll have to create aliases or nested criteria:

session.createCriteria(Employee.class)
 .createAlias("address", "a")
 .add(Restrictions.eq("a.postalCode", postalCode));

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