Hibernate : Component Mapping

Overview:
This article looks at how you can map data in a given table across several POJOs treated as components of another POJO.

Association Diagram
 __________
|Person    |
 ----------
     |
 ____|_____
|Address   |
 ----------

The above relationship corresponds into the following Class Diagram, which indicates that a given Person has a single Address associated.

 
 ----------------
|Person          |
|----------------|
|id:long         |
|name:String     |
|address:Address |
----------------

 ----------------
|Address         |
|----------------|
|line1:String    |
|line2:String    |
|city:String     |
|state:String    |
|zipCode:String  | 
 ----------------

However, we will store both the above entities in a single table. And the database structure is as follows,

 CREATE TABLE PERSON (
  person_id INTEGER NOT NULL,
  name VARCHAR(50),
  line1 VARCHAR(50),
  line2 VARCHAR(50),
  city VARCHAR(25),
  state VARCHAR(25),
  zip-code VARCHAR(25),
);

Lets look at the Hibernate mapping that involves in mapping both the entities into a single table.

 <?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
   "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping>
    <class name="org.fazlan.Person" table="PERSON">
         <id name="id" column="person_id">
              <generator class="increment" />
         </id>
         <property name="name"/>
         <component name="address" class="org.fazlan.Address">
              <proeprty name="line1" />
              <proeprty name="line2" />
              <proeprty name="city" />
              <proeprty name="state" />
              <proeprty name="zipCode" column="zip-code"/>
         </component>
    </class>
</hibernate-mapping>

That's all about it!