Single Table策略

通过 discriminator鉴别器来区分是父类还是子类

模型对象

父类Employee

public class Employee {
  private Long id;
  private String name;

子类HourlyEmployee

public class HourlyEmployee extends Employee {
  private Double rate;

子类SalariedEmployee

public class SalariedEmployee extends Employee {
  private Double salary;

映射文件Employee.hbm.xml

<class name="Employee" table="t_employee" discriminator-value="1">
        <id name="id">
            <generator class="native" />
        </id>
        <!-- 在id之后配置discriminator的数据库类型的字段名称 ,以及类型(默认是string) -->
        <discriminator column="types" type="int" />
        <property name="name" />
        <!-- 在配置子类 -->
        <subclass name="HourlyEmployee" discriminator-value="2">
            <property name="rate"/>
        </subclass>
        <subclass name="SalariedEmployee" discriminator-value="3">
            <property name="salary" />
        </subclass>
    </class>

测试对象MainTest

public class MainTest {
  Session session = null;
  @Before
  public void save() {
    session = HibernateUtils.INSTANCE.getSession();
    session.beginTransaction();

    Employee employee = new Employee("jege");

    HourlyEmployee hourlyEmployee = new HourlyEmployee();
    hourlyEmployee.setName("hourly");
    hourlyEmployee.setRate(200D);

    SalariedEmployee salariedEmployee = new SalariedEmployee();
    salariedEmployee.setName("salaried");
    salariedEmployee.setSalary(300D);

    session.save(employee);
    session.save(hourlyEmployee);
    session.save(salariedEmployee);
  }

  @Test
  public void get() {
    Employee employee = (Employee) session.get(Employee.class, 1L);
    System.out.println(employee.getName());

    HourlyEmployee hourlyEmployee = (HourlyEmployee) session.get(HourlyEmployee.class, 2L);
    System.out.println(hourlyEmployee.getName());
    System.out.println(hourlyEmployee.getRate());

    SalariedEmployee salariedEmployee = (SalariedEmployee) session.get(SalariedEmployee.class, 3L);
    System.out.println(salariedEmployee.getName());
    System.out.println(salariedEmployee.getSalary());
  }

  @After
  public void colse() {
    session.getTransaction().commit();
    session.close();
  }
}

源码地址

https://github.com/je-ge/hibernate

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