hibernate--リレーショナルマッピング

              ，            ，    
Hibernate              :

1、  N-1

2、  1-1

3、  1-N

4、  N-N

5、  1-N

6、  N-N

7、  1-1

                      :

 

 、      

   POJO

public class Person{

 

private int pid;

private String name;

private Address address;

 

...//     getter、setter  

}

----------------------------------------

public class Address{

private int id;

private String detail;

...//     getter、setter  

 

}

 

              Person         ,     N-1                          

**     

<class name="Person">

<id name="id">

<generator class="native"/>

</id>

...//        

<many-to-one name="address" column="addressId"/>//    

</class>

      hibernate          （Person）      addressId      

 

 

 、   1-1(    )

    <many-to-one>  ，       unique=true，                

                 

          :

<many-to-one name="address" column="addressId" unique="true"/>

 

 、   1-N

**   ,             ，        1-N  

public class Classes {
 private int id;
 private String name;
 private Set students; 

...//     getter、setter  

}

---------------------------------------------------------------------------

public class Student {
 private int id;
 private String name;

 

..//     getter、setter  

}

**    :       ，                 ,           

**    :

<class name="Classes" table="t_classes">
  <id name="id">
   <generator class="native"/>
  </id>
  <property name="name"/>
  <set name="students">
   <key column="classesid"/>//                (          )
   <one-to-many class="xxx.Student"/>//              
  </set>
 </class>

 

 

 、  1-N

        1-N                  ,     1-N    N-N，        <one-to-many>

        ，   <many-to-many>  ，          ，      unique="true"  

**  ,      1-N     

<class name="xxx.Classes" table="t_classes">
  <id name="id">
   <generator class="native"/>
  </id>
  <property name="name"/>
  <set name="students">
   <key column="classesid"/>

   <many-to-many class="xxx.Student" unique="true"/>
  </set>
 </class>

 

 、     

 

**    POJO

public class User {
 private int id;
 private String name;
 private Set roles; 

 ..//     getter、setter  

}

---------------------------------------------------------------------------

public class Role {
 private int id;
 private String name;

..//     getter、setter  

}

         N-N  ，  User     Role，   Role      User   

          N-N       N-1   

**     

 

<class name="xxx.User" table="t_user">
  <id name="id">
   <generator class="native"/>
  </id>
  <property name="name"/>
  <set name="roles" table="t_user_role">
   <key column="userid"/>
   <many-to-many class="xxx.Role" column="roleid"/>
  </set>
 </class>

            

  t_user                t_user_role                     t_role      

 id  name   < -------userid     roleid   ----- >     id     name

 

 

  、        

                    ，        

       N-N  

 Role       

public class Role {
 private int id;
 private String name;

privarte Set user

..//     getter、setter  

}

 

       

<class name="xxx.User" table="t_user">
  <id name="id">
   <generator class="native"/>
  </id>
  <property name="name"/>
  <set name="roles" table="t_user_role">
   <key column="userid"/>
   <many-to-many class="xxx.Role" column="roleid"/>
  </set>
 </class>

 ------------------------------------------------------------------------------------------------

<class name="xxx.Role" table="t_role">
  <id name="id">
   <generator class="native"/>
  </id>
  <property name="name"/>
  <set name="users" table="t_user_role" order-by="userid">
   <key column="roleid"/>
   <many-to-many class="xxx.User" column="userid"/>
  </set>
 </class>

   :1、                           

           2、      Set table     ,      

 

 、        

   1-1       :

1、       1-1  

               1-1  ,   N-1     ，    <many-to-one>        unique="true"          1-1    ,                 ?

 

         ：  User         identityId

      POJO 

public class Person {

 private int id;
 private String name;
 private IdentityId identityId; 

..//     getter、setter  

}

public class IdentityId {
 private int id;
 private String cardNo;
 private Person person;

..//     getter、setter  

}

**     

<class name="xxx.Person" table="t_person">
  <id name="id">
   <generator class="native"/>
  </id>
  <property name="name"/>
  <many-to-one name="identityId" class="xxx.IdentityId" unique="true"/>
 </class>

-----------------------------------------------------------------------------------

<class name="xxx.IdentityId" table="t_identity">
  <id name="id">
   <generator class="native"/>
  </id>
  <property name="cardNo"/>
  <one-to-one name="person" class="xxx.Person" property-ref="identityId"/>
 </class>

   ：   property-ref   identity      identity   person     .

      identity      getIdentityId()        Person       ：

Person   IdentityId            person.getIdentityId().getPerson()

2、     1-1    

   POJO         ，           

 

<class name="xxx.Person" table="t_person">
  <id name="id" column="ID">
   <generator class="foreign">
    <param name="property">identityId</param>
   </generator>
  </id>
  <property name="name"/>
  <one-to-one name="identity" clsss="xxx.IdentityId" constrained="true"/>
 </class>

  ：   constrained="true"  Person    ID        IdentityId 

--------------------------------------------------------------------------------------

<class name="xxx.Identity" table="t_identity">
  <id name="id">
   <generator class="native"/>
  </id>
  <property name="cardNo"/>
  <one-to-one name="person" class="xxx.Person"/>
 </class>

   ：  Person  ID              IdentityId,     foreign       Hibernate    Person

      IdentityId        

                                         
                                   (   )    (   )            

             ，       ，     ，             ，            。
                  ，       ，                       ？       ，     。       ，      ，       。
                   。