组成关系

在一个员工模型里面需要存入
员工公司所在地址的城市，街道
员工籍贯所在的城市，街道，
此时可以抽取城市，街道变成一个模型即是组成关系

模型对象Employee

public class Employee {
  private Long id;
  private String name;
  // 公司的地址
  private Address comAddress;
  // 籍贯所在地
  private Address homeAddress;

映射文件Employee.hbm.xml

<class name="Employee" table="t_employee">
        <id name="id">
            <generator class="native" />
        </id>
        <property name="name" />
        <!-- 组成关系:以对象的方式来解决重复的信息 -->
        <!-- 公司所在的地址 -->
        <!-- class必须配置为全类名 -->
        <component name="comAddress" class="Address">
            <!-- property:name必须配置成java的属性，column配置成数据库的字段，而且不能重复 -->
            <property name="city" column="com_city" />
            <property name="street" column="com_street" />
        </component>
        <!-- 籍贯所在的地址 -->
        <component name="homeAddress" class="Address">
            <property name="city" column="home_city" />
            <property name="street" column="home_street" />
        </component>
    </class>

测试对象MainTest

public class MainTest {
  Session session = null;

  @Before
  public void save() {
    session = HibernateUtils.INSTANCE.getSession();
    session.beginTransaction();
    Address comAddress = new Address("bj", "st1");
    Address homeAddress = new Address("sh", "st2");

    Employee employee = new Employee("user");
    employee.setComAddress(comAddress);
    employee.setHomeAddress(homeAddress);

    session.save(employee);
  }

  @Test
  public void get() throws Exception {
    Employee employee = (Employee) session.get(Employee.class, 1L);
    System.out.println(employee);
    System.out.println(employee.getComAddress());
    System.out.println(employee.getHomeAddress());
  }

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

源码地址

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

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