Hibernate 关联关系映射配置

Hibernate 关联关系映射配置

1. 问题背景

   • 一个部门下有多个员工，每个员工只属于一个部门
   • 员工对部门（多对一）
   • 部门对员工（一对多）

2. 配置关联关系

   • 实体类

     Employee.java

     public class Employee {
     	private  Department department;
     
         private Integer employeeID;
         private String employeeName;
         private String sex;
         private Date birthday;
         private Date joinDate;
         private String employeeNo;
         private  String username;
         private String password;
         //getter setter
     }
     

     Department.java

     public class Department {
     	private Set<Employee> employees=new HashSet<Employee>();
     
         private Integer departmentID;
         private String departmentName;
         private String departmentDesc;   
         //getter setter
     }
     

   • Employee.hbm.xml中多对一的配置

     <!--关联关系映射-->
     <many-to-one name="department" class="domain.Department" column="depID"/>
     

   • Department.hbm.xml中一对多的配置

     <!--关联关系映射-->
     <set name="employees">
         <key column="depID"/>
         <one-to-many class="learn.ssh_employee.domain.Employee" />
     </set>
     

3. 附完整版配置

   Employee.hbm.xml中多对一的配置

   <!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN" "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
   <hibernate-mapping>
       <class name="learn.ssh_employee.domain.Employee" table="employee">
           <id name="employeeID" column="employeeID">
               <generator class="native"/>
           </id>
   
           <property name="employeeName" column="employeeName" length="20"/>
           <property name="sex" column="sex" length="10" />
           <property name="birthday" column="birthday"/>
           <property name="joinDate" column="joinDate"/>
           <property name="employeeNo" column="employeeNo" length="20"/>
           <property name="username" column="username" length="20"/>
           <property name="password" column="password" length="20"/>
   
           <!--关联关系映射-->
           <many-to-one name="department" class="learn.ssh_employee.domain.Department" column="depID"/>
       </class>
   </hibernate-mapping>
   

   Department.hbm.xml中一对多的配置

   <!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN" "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
   <hibernate-mapping>
       <class name="learn.ssh_employee.domain.Department" table="department">
           <id name="departmentID" column="departmentID">
               <generator class="native"/>
           </id>
   
           <property name="departmentName" column="departmentName" length="20"/>
           <property name="departmentDesc" column="departmentDesc" />
   
           <!--关联关系映射-->
           <set name="employees">
               <key column="depID"/>
               <one-to-many class="learn.ssh_employee.domain.Employee" />
           </set>
   
       </class>
   </hibernate-mapping>