Hibernate 系列教程9-自关联

自关联:本质还是原来双向一对多,原来要配置两个类，现在全部都配置在一个类里面

Employee

public class Employee {
  private Long id;
  private String name;
  // 多对一： 多个员工对一上级
  private Employee manager;
  // 一对多：一个领导有多个下级
  private Set<Employee> children = new HashSet<Employee>();

Employee.hbm.xml

<class name="Employee" table="t_employee">
        <id name="id">
            <generator class="native" />
        </id>
        <property name="name" />
        <!-- private Employee manager;// 多对一： 多个员工对一上级 -->
        <many-to-one name="manager" column="manager_id" class="Employee"/>
        <!-- private Set<Employee> children = new HashSet<Employee>();// 一对多：一个领导有多个下级 -->
        <set name="children" inverse="true" cascade="save-update">
            <key column="manager_id" />
            <one-to-many class="Employee" />
        </set>
    </class>

MainTest

public class MainTest {
  Session session = null;

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

    Employee boss = new Employee("boss");
    Employee manager = new Employee("manager");
    Employee emp1 = new Employee("emp1");
    Employee emp2 = new Employee("emp2");

    manager.addEmployee(emp1).addEmployee(emp2);
    boss.addEmployee(manager);

    session.save(boss);

  }

  @Test
  public void get() {
    Employee boss = (Employee) session.get(Employee.class, 1L);
    System.out.println("boss:" + boss.getName());
    Set<Employee> employees = boss.getChildren();
    for (Employee manager : employees) {
      System.out.println("manager:" + manager.getName());
      Set<Employee> children = manager.getChildren();
      for (Employee employee : children) {
    System.out.println("employee:" + employee.getName());
      }
    }
  }

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

源码地址

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

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