Hibernate 继承映射实现方式之每个具体类对应一张表

参考链接

父类和子类分放在不同的表中，子类通过父类的id与父类关联。只有父类有配置文件，父类中通过joined-subclass标识子类.

现在有四个类Employee2、SalaryEmployee2、HourlyEmployee2，其中Employee是SalaryEmployee、HourlyEmployee的父类

类的实现代码如下：Employee2

package com.supporter.prj.bm.period_manage.entity;
public class Employee2 {	
	private String employeeId; 
	private String name;	
	public String getEmployeeId() {	
		return employeeId;
	}
	public void setEmployeeId(String employeeId) {
		this.employeeId = employeeId;
	}
	public String getName() {
		return name;
	}
	public void setName(String name) {		
		this.name = name;
	}

}

HourlyEmployee2

public class HourlyEmployee2 extends Employee2{
	private Double rate;
	public Double getRate() {
		return rate;
	}
	public void setRate(Double rate) {
		this.rate = rate;
	}
}

SalaryEmployee2

<span style="font-size:14px;">package com.supporter.prj.bm.period_manage.entity;
public class SalaryEmployee2 extends Employee2{
	private Double salary;
	public Double getSalary() {
		return salary;
	}
	public void setSalary(Double salary) {	
		this.salary = salary
	} 
}</span>

数据库：employee2

hourlyEmployee2(没有将主键设置为外键)

salaryEmployee2(没有将主键设置为外键)

hibernate文件：

<?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.supporter.prj.bm.period_manage.entity"> 
    <class name="Employee2" table="bm_employee2">  
        <id name="employeeId" type="string" column="employee_id">
	<span style="white-space:pre">	</span><generator class="assigned"/>
	</id>
	<property name="name" column="name" type="string" length="16"/>  
        <joined-subclass name = "SalaryEmployee2" table="bm_salary_employee2">  
            <key column = "employee_id"></key>  
            <property name="salary" column="salary" type="java.lang.Double" />  
        </joined-subclass>  
        <joined-subclass name = "HourlyEmployee2" table="bm_hourly_employee2">  
            <key column = "employee_id"></key>  
            <property name="rate" column="rate" type="java.lang.Double">  
            </property>  
        </joined-subclass>  
    </class>  
</hibernate-mapping>

业务逻辑

package com.supporter.prj.bm.period_manage.service;
import java.util.List;
import org.springframework.beans.factory.annotation.Autowired;
import com.supporter.prj.bm.period_manage.dao.HourlyEmployee2Dao;
import com.supporter.prj.bm.period_manage.entity.HourlyEmployee2;
public class EmployeeService {
	@Autowired
	private HourlyEmployee2Dao hourlyEmployeeDao;
	public void gethourlyEmployee() {
		/**
		 * hql:from HourlyEmployee2
		 * 包装的retrieve方法
		 */
		List <HourlyEmployee2> hourlyE = hourlyEmployeeDao.getAllObjects();
	}

执行的sql语句：

SELECT
    hourlyempl0_.employee_id AS employeeId,
    hourlyempl0_1_.name      AS name,
    hourlyempl0_.rate        AS rate
FROM
    bm_hourly_employee2 hourlyempl0_,
    bm_employee2 hourlyempl0_1_
WHERE
    hourlyempl0_.employee_id=hourlyempl0_1_.employee_id

执行结果：

参考：

原employee2表中数据：

hourlyEmployee2表中的数据：

增加数据：

Action:

public void gethourlyEmployee(){
	SalaryEmployee2 salaryEmployee = new SalaryEmployee2();
	salaryEmployee.setEmployeeId("000003");
	salaryEmployee.setName("hali");
	salaryEmployee.setSalary(200000.0);
		
	HourlyEmployee2 hourlyEmployee = new HourlyEmployee2();
	hourlyEmployee.setEmployeeId("000004");
	hourlyEmployee.setName("jexika");
	hourlyEmployee.setRate(0.09);
	employeeService.saveH(salaryEmployee, hourlyEmployee);
	employeeService.gethourlyEmployee();
}

Service

public void saveH(SalaryEmployee2 salaryEmployee, HourlyEmployee2 hourlyEmployee) {

<span style="white-space:pre">	</span>//注释的方式和下面实现结果，执行的sql语句都一样。
	//employeeDao.save(hourlyEmployee);
	//employeeDao.save(salaryEmployee);
	hourlyEmployeeDao.save(hourlyEmployee);
	salaryEmployeeDao.save(salaryEmployee);
		
}

保存子类到相应的子表的同时，相应的父类数据会保存到父类表

执行结果：

执行语句：

Hibernate: 
    insert 
    into
        bm_employee2
        (name, employee_id) 
    values
        (?, ?)
Hibernate: 
    insert 
    into
        bm_hourly_employee2
        (rate, employee_id) 
    values
        (?, ?)
Hibernate: 
    insert 
    into
        bm_employee2
        (name, employee_id) 
    values
        (?, ?)
Hibernate: 
    insert 
    into
        bm_salary_employee2
        (salary, employee_id) 
    values
        (?, ?)

删除数据：

action

public void delEmployee(){
		employeeService.delEmloyee();
	}

Service

public void delEmloyee() {
	hourlyEmployeeDao.delete("000004");
	salaryEmployeeDao.delete("000003");
}

删除子表已有的数据的同时，相应的父类数据也会删除相应id的数据

执行结果

执行的sql语句：

Hibernate: 
    select
        hourlyempl0_.employee_id as employee1_3558_0_,
        hourlyempl0_1_.name as name3558_0_,
        hourlyempl0_.rate as rate3560_0_ 
    from
        bm_hourly_employee2 hourlyempl0_,
        bm_employee2 hourlyempl0_1_ 
    where
        hourlyempl0_.employee_id=hourlyempl0_1_.employee_id 
        and hourlyempl0_.employee_id=?
Hibernate: 
    select
        salaryempl0_.employee_id as employee1_3558_0_,
        salaryempl0_1_.name as name3558_0_,
        salaryempl0_.salary as salary3559_0_ 
    from
        bm_salary_employee2 salaryempl0_,
        bm_employee2 salaryempl0_1_ 
    where
        salaryempl0_.employee_id=salaryempl0_1_.employee_id 
        and salaryempl0_.employee_id=?
Hibernate: 
    delete 
    from
        bm_hourly_employee2 
    where
        employee_id=?
Hibernate: 
    delete 
    from
        bm_employee2 
    where
        employee_id=?
Hibernate: 
    delete 
    from
        bm_salary_employee2 
    where
        employee_id=?
Hibernate: 
    delete 
    from
        bm_employee2 
    where
        employee_id=?