Hibernate学习4：一对多关联映射

文章目录

1. 1. 实体类（JavaBean）
   1. 1.1. Department.java
   2. 1.2. Employee.java
2. 2. Department.hbm.xml
   1. 2.1. set
   2. 2.2. key
   3. 2.3. one-to-many

接续上一篇博客：如果我们从部门的角度去考虑部门和员工的关系，那么两者的关系就变为了一对多（一个部门对应多个员工）。我们继续用例子来说明一对多关联关系。

实体类（JavaBean）

Department.java

public class Department {
	private int id;
	private String name;

	private Set<Employee> emps;

    //省略get、set方法
}

Employee.java

public class Employee {
	private int id;
	private String name;
	private Department depart; 
    //省略get、set方法
}

Department.hbm.xml

<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC 	"-//Hibernate/Hibernate Mapping DTD 3.0//EN"	"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
	"-//Hibernate/Hibernate Mapping DTD 3.0//EN"
	"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping package="cn.zju.domain">
	<class name="Department">
		<id name="id">
			<generator class="native" />
		</id>
		<property name="name"/>
        <set name="emps">
          <key column="depart_id"></key>
          <one-to-many class="Employee" />
         </set>
	</class>
</hibernate-mapping>

Hibernate提供one-to-many标签来实现一对多关联关系：

<set name="emps">
    <key column="depart_id"></key>
    <one-to-many class="Employee" />
</set>

set

name属性：指向待映射的持久化类

key

设定与所关联的持久化类对应的表的外键

• column: 指定关联表的外键名

  one-to-many

  设定集合属性中所关联的持久化类
• class: 指定关联的持久化类的类名