A brief analysis of Hibernate mapping (II.)--Relational mapping (5)

One-way many-to-many association mappings

One-way many-to-many association object model:

The mapped relational model:

Many-to-many mappings produce a third table to maintain relationships

Map file:

User.hbm.xml

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2. <? XML version="1.0"?>
4. <! DOCTYPE hibernate-mapping Public
6. "-//hibernate/hibernate Mapping DTD 3.0//en"
8. "Http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
10. <hibernate-mapping package="Com.jialin.hibernate">
12. <class name="User" table="T_user">
14. <ID name="id">
16. <generator class="native" />
18. </ID>
22. <property name="name" />
24. <set name= "roles" table="T_user_role">
26. <key column="userid" />
28. <many-to-many class="Role" column="Roleid" />
30. </Set>
32. </class>
34. </hibernate-mapping>

Role.hbm.xml

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2. <? XML version="1.0"?>
4. <! DOCTYPE hibernate-mapping Public
6. "-//hibernate/hibernate Mapping DTD 3.0//en"
8. "Http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
10. <hibernate-mapping package="Com.jialin.hibernate">
12. <class name="Role" table="T_role">
14. <ID name="id">
16. <generator class="native" />
18. </ID>
22. <property name="name" />
26. </class>
30. </hibernate-mapping>

Bidirectional many-to-many association mappings

Bidirectional many-to-many association object model

The mapped relational model is the same as the one-way.

The mapping method is basically the same, just adding at the end of the multiple:
<set name= "Users" table= "T_user_role" >
<key column= "role_id" not-null= "true"/>
<many-to-many class= "Com.bjpowernode.hibernate.User" column= "user_id"/>
</set>

Need to note:
* The resulting intermediate table name must be the same
* The fields in the resulting intermediate table must be the same

A brief analysis of Hibernate mapping (II.)--Relational mapping (5)