An implementation of an inheritance mapping for Hibernate (subclass + join)

<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC
	"-//Hibernate/Hibernate Mapping DTD//EN"
	"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd" >

<hibernate-mapping package="com.test.entity">
	<class
		name="Employee"
		table="test_employee"
		discriminator-value="0"
	>
		<meta attribute="sync-DAO">false</meta>
		<id
			name="id"
			type="string"
			column="emp_id"
		>
			<generator class="assigned"/>
		</id>
		<discriminator column="emp_type" type="int"/>
                <property name="empName" column="emp_name" />
                <property name="sex" column="sex" />
                <property name="age" column="age" />
                <subclass name="Leader" discriminator-value="1" >
			<join table="test_leader" fetch="select">   
				<key column="emp_id" foreign-key="id"/>
				<property name="empName" column="emp_name" />
                                <property name="sex" column="sex" />
                                <property name="age" column="age" />
                                <property name="post" column="post" />
			</join>
		</subclass>
                <subclass name="Manager" discriminator-value="2" >
			<join table="test_manager" fetch="select">   
				<key column="emp_id" foreign-key="id"/>
				<property name="empName" column="emp_name" />
                                <property name="sex" column="sex" />
                                <property name="age" column="age" />
                                <property name="deptId" column="dept_id" />
			</join>
		</subclass>
                <subclass name="Staff" discriminator-value="3" >
			<join table="test_staff" fetch="select">   
				<key column="emp_id" foreign-key="id"/>
				<property name="empName" column="emp_name" />
                                <property name="sex" column="sex" />
                                <property name="age" column="age" />
                                <property name="job" column="job" />
			</join>
		</subclass>
...

 

Relational model (4 separate database tables):

Enterprise employee: Employee(emp_id,emp_name,sex,age,emp_type)

                  emp_type (1: business leaders, 2: managers, 3: ordinary employees)

                  Data: emp_id_1, leader 1, male, 45, 1

                             emp_id_2, management 1, male, 36, 2

                             emp_id_3, employee 1, male, 22, 3

Business leader: Leader(emp_id,emp_name,sex,age, post )

                  Data: emp_id_1, leader 1, male, 45, 1

Manager: Manager(emp_id,emp_name,sex,age, dept_id )

                  Data: emp_id_2, admin 1, male, 36, 2

Ordinary employee: Staff (emp_id,emp_name,sex,age, job )

                  Data: emp_id_3, employee 1, male, 22, 3

 

Among them: enterprise employees = enterprise leaders + managers + ordinary employees