An analysis of Hibernate mapping (iv)--component mapping (component)

Component mapping

In hibernate, the component map uses <component> tags to

Component is the logical component of an entity, and the main difference between it and the entity class is that it has no OID
Component is called a value class in DDD

The advantages of using component: To realize the fine-grained division of the object model, high reuse rate, clear meaning and distinct hierarchy

Object model and relational model design on the contrary, the object model is generally fine-grained, and the relational model is generally coarse-grained.

Example:

Object Model:

Relational Model:

Map file:

Employee.hbm.xml

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2. <hibernate-mapping>
4. <class name="Com.jialin.hibernate.Employee" table="T_emplyee">
6. <ID name="id">
8. <generator class="native"/>
10. </ID>
12. <property name="name"/>
14. <component name="Employeecontact">
16. <property name="email"/>
18. <property name="Address"/>
20. <property name="ZipCode"/>
22. <property name="Contacttel"/>
24. </Component>
26. </class>
28. </hibernate-mapping>

User.hbm.xml

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2. <hibernate-mapping>
4. <class name="Com.jialin.hibernate.User" table="T_user">
6. <ID name="id">
8. <generator class="native"/>
10. </ID>
12. <property name="name"/>
14. <component name="Usercontact">
16. <property name="email"/>
18. <property name="Address"/>
20. <property name="ZipCode"/>
22. <property name="Contacttel"/>
24. </Component>
26. </class>
28. </hibernate-mapping>

An analysis of Hibernate mapping (iv)--component mapping (component)