Hibernate's mapping composition relationship

Establishing a domain model (the Java object Model) and a relational data Model (database table model) have different starting points:
Domain model: consists of program code that improves the reusability of code by refining the granularity of the persisted class (that is, by planning the same attribute as a class) to simplify programming
　　Relational model: In the absence of data redundancy, you should minimize the number of tables and simplify the referential relationships between tables to improve data access speed

Hibernate divides the properties of a persisted class into two types:
Value type: No OID, cannot be persisted independently, life cycle depends on the life cycle of the object of the owning persisted class
Entity type: Has OID, can be persisted independently, has independent life cycle obviously cannot map entity class attribute directly with property
Hibernate uses the <component> element to map the constituent relationships (that is, it is possible that multiple persisted classes form a table), the element table name pay property is a component of the Worker class, which is called a component in Hibernate

Example:
Create a new worker class:

 Packagecom.atguigu.hibernate.entities; Public classWorker {PrivateInteger ID; PrivateString name; PrivatePay pay ;  PublicInteger getId () {returnID; }     Public voidsetId (Integer id) { This. ID =ID; }     PublicString GetName () {returnname; }     Public voidsetName (String name) { This. Name =name; }     PublicPay Getpay () {returnPay ; }     Public voidSetPay (Pay pay) { This. Pay =Pay ; }            }

The worker class also contains a pay class:

 Packagecom.atguigu.hibernate.entities; Public classPay {Private intMonthlypay; Private intYearpay; Private intVocationwithpay; Privateworker worker;  PublicWorker Getworker () {returnworker; }     Public voidSetworker (worker worker) { This. Worker =worker; }     Public intGetmonthlypay () {returnMonthlypay; }     Public voidSetmonthlypay (intMonthlypay) {         This. Monthlypay =Monthlypay; }     Public intGetyearpay () {returnYearpay; }     Public voidSetyearpay (intYearpay) {         This. Yearpay =Yearpay; }     Public intGetvocationwithpay () {returnVocationwithpay; }     Public voidSetvocationwithpay (intVocationwithpay) {         This. Vocationwithpay =Vocationwithpay; }            }

The question is, how to put these two classes at the same time in a table???

Can be configured with a. hbm.xml file

We can use the <component> tag to specify the classes contained in a class

　　

<?XML version= "1.0"?><!DOCTYPE hibernate-mapping Public "-//hibernate/hibernate mapping DTD 3.0//en" "http://hibernate.sourceforge.net/ Hibernate-mapping-3.0.dtd "><!--Generated 2014-1-2 16:14:33 by Hibernate Tools 3.4.0.CR1 -<hibernate-mapping Package= "Com.atguigu.hibernate.entities">    <classname= "Worker"Table= "WORKER">        <IDname= "id"type= "Java.lang.Integer">            <columnname= "ID" />            <Generatorclass= "Native" />        </ID>        < Propertyname= "Name"type= "Java.lang.String">            <columnname= "NAME" />        </ Property>                <!--Mapping Composition Relationships -        <Componentname= "Pay"class= "Pay">            <Parentname= "worker"/>            <!--Specifies the properties of the component that makes up the relationship -            < Propertyname= "Monthlypay"column= "Monthly_pay"></ Property>            < Propertyname= "Yearpay"column= "Year_pay"></ Property>            < Propertyname= "Vocationwithpay"column= "Vocation_with_pay"></ Property>        </Component>            </class></hibernate-mapping>

This allows you to designate multiple persisted classes as a single table,

　　　　

Hibernate's mapping composition relationship