java - Hibernate - 在 xml 中不相关对象上映射关联

Question

我有两门课:

• 用户

• 租车

  public class User implements Serializable{
      private String userName;
      private Integer userId;
      private String userParent;
  }
  
  public class RentedCar implements Serializable{
      private Date stopDate;
      private Date startDate;
      private String carName;
      private Integer carId;
      private Integer userId;   // Some userId from User.
  }
  

这些类有各自的hbm.xml 文件。基础表不相关。这意味着我知道 RentedCar 中的 userId 与 User 中的 userId 关联，但没有 PK/FK 他们之间的关系。我需要在 RentedCar 和 User 之间添加多对一关联以及一对多关联在User 和RentedCar 之间。我应该如何在 hbm.xml 文件中执行此操作？

这些是 xml 映射:

<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE hibernate-mapping PUBLIC 
 "-//Hibernate/Hibernate Mapping DTD//EN"
 "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">

 <hibernate-mapping>
    <class name="User" table="user">
        <composite-id>
            <key-property name="userName" column="user_name" type="string"/>
            <key-property name="userParent" column="user_parent" type="string"/>
        </composite-id>
        <property name="userId" column="user_id" type="int"></property>
    </class>
 </hibernate-mapping>



<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE hibernate-mapping PUBLIC 
 "-//Hibernate/Hibernate Mapping DTD//EN"
 "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">

 <hibernate-mapping>
    <class name="RentedCar" table="rented_car">
        <composite-id>
            <key-property name="stopDate" column="stop_date" type="date" />
            <key-property name="carId" column="car_id" type="int" />
            <key-property name="userId" column="user_id" type="int" />
        </composite-id>
        <property name="startDate" column="start_date" type="date"></property>
        <property name="carName" column="car_name" type="float"></property>
    </class>
 </hibernate-mapping>

Answer 1

我认为您的类中应该有一些内容表明存在一对多关系，以便在 hbm.xml 文件中执行此操作:

public class User implements Serializable{
    private String userName;
    private Integer userId;
    private String userParent;
    private Set<RentedCar> rentedCars;
}

public class RentedCar implements Serializable{
    private Date stopDate;
    private Date startDate;
    private String carName;
    private Integer carId;
    private User user; 
}

然后在 RentedCar.hbm.xml 中您可以在里面使用:

<many-to-one name="user" class="User">
        <column name="userId" not-null="true"></column>
 </many-to-one>

在 User.hbm.xml 中:

<set name="rentedCars" table="rented_car" fetch="select">
     <key>
          <column name="userId" not-null="true"></column>
     </key>
     <one-to-many class=" RentedCar "/>
 </set>

本教程可能对您有帮助 http://www.tutorialspoint.com/hibernate/hibernate_one_to_many_mapping.htm