Hibernate_映射_关联关系_一对多多对一映射1

值类型的集合
  集合元素是普通类型
实体类型的集合
  集合元素是另外一个实体

  一对多                     多对一
Department.hbm.xml              Employee.hbm.xml
  要说明的信息有：            要说明的信息有：
  1,集合表(员工表)              1,关联的是什么类型
  2,集合外键                2,外键列
  3,集合元素                  
    关联的实例类型

部门映射文件

<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC
        "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
        "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<!-- 导入包 -->
<hibernate-mapping package="cn.itcast.f_hbm_oneToMany">
  <!-- 类名 -->
  <class name="Department" table="department">
    <id name="id" type="integer" column="id_">
      <generator class="native" />
    </id>
    <property name="name" type="string" column="name_" />
    <!-- employee属性,Set集合,表达的是本类与Employee的一对多关系 -->
    <set name="employee">
      <key column="departmentId" />
      <one-to-many class="Employee" />
    </set>
  </class>
</hibernate-mapping>

员工映射文件

<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC
        "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
        "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<!-- 导入包 -->
<hibernate-mapping package="cn.itcast.f_hbm_oneToMany">
  <!-- 类名 -->
  <class name="Employee" table="employee">
    <id name="id" type="integer" column="id_">
      <generator class="native" />
    </id>
    <property name="name" type="string" column="name_" />

    <!-- department属性,表达的是本类与Department的多对一的关系 -->
    <many-to-one name="department" class="Department" column="departmentId"></many-to-one>
  </class>
</hibernate-mapping>

部门实例

package cn.itcast.f_hbm_oneToMany;

import java.util.HashSet;
import java.util.Set;

/**
 * 部门
 * 
 * @author 风清杨
 * @version V3.0
 * 
 */
public class Department {
  /** 部门id */
  private Integer id;
  /** 部门名称 */
  private String name;
  /** 员工信息 */
  private Set<Employee> employee = new HashSet<Employee>();// 关联的很多员工

  public Integer getId() {
    return id;
  }

  public void setId(Integer id) {
    this.id = id;
  }

  public String getName() {
    return name;
  }

  public void setName(String name) {
    this.name = name;
  }

  public Set<Employee> getEmployee() {
    return employee;
  }

  public void setEmployee(Set<Employee> employee) {
    this.employee = employee;
  }

  @Override
  public String toString() {
    return "Department [id=" + id + ", name=" + name + "]";
  }

}

员工实例

package cn.itcast.f_hbm_oneToMany;

/**
 * 员工部门
 * 
 * @author 风清杨
 * @version V3.0
 * 
 */
public class Employee {
  /** 员工编号 */
  private Integer id;
  /** 员工姓名 */
  private String name;

  /** 员工部门 */
  private Department department;// 关联的部门对象

  public Integer getId() {
    return id;
  }

  public void setId(Integer id) {
    this.id = id;
  }

  public String getName() {
    return name;
  }

  public void setName(String name) {
    this.name = name;
  }

  public Department getDepartment() {
    return department;
  }

  public void setDepartment(Department department) {
    this.department = department;
  }

  @Override
  public String toString() {
    return "Employee [id=" + id + ", name=" + name + "]";
  }

}

测试类

package cn.itcast.f_hbm_oneToMany;

import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.Transaction;
import org.hibernate.cfg.Configuration;
import org.junit.Test;

/**
 * 应用程序操作类
 * 
 * @author 风清杨
 * @version V3.0
 * 
 */
public class App {
  private static SessionFactory sessionFactory = new Configuration()//
      .configure()//
      .addClass(Department.class)//
      .addClass(Employee.class)//
      .buildSessionFactory();

  // 保存,有关联关系
  @Test
  public void testSave() throws Exception {
    Session session = sessionFactory.openSession();
    Transaction tx = null;
    try {
      tx = session.beginTransaction();
      // ------------------------------------

      // 新建对象
      Department department = new Department();
      department.setName("开发部");

      Employee employee1 = new Employee();
      employee1.setName("张三");

      Employee employee2 = new Employee();
      employee2.setName("李四");

      // 关联起来
      employee1.setDepartment(department);
      employee2.setDepartment(department);
      department.getEmployee().add(employee1);
      department.getEmployee().add(employee2);

      // 保存
      session.save(department);
      session.save(employee1);
      session.save(employee2);
      // ------------------------------------
      tx.commit();
    } catch (RuntimeException e) {
      tx.rollback();
      throw e;
    } finally {
      session.close();
    }
  }

  // 获取,可以获取到关联的对方
  @Test
  public void testGet() throws Exception {
    Session session = sessionFactory.openSession();
    Transaction tx = null;
    try {
      tx = session.beginTransaction();
      // ------------------------------------

      // 获取一方数据,并显示另一方信息
      //Department department = (Department) session.get(Department.class,
      // 1);
      // System.out.println(department);
      // System.out.println(department.getEmployee());
      Employee employee = (Employee) session.get(Employee.class, 1);
      System.out.println(employee);
      System.out.println(employee.getDepartment());

      // ------------------------------------
      tx.commit();
    } catch (RuntimeException e) {
      tx.rollback();
      throw e;
    } finally {
      session.close();
    }
  }
}