hibernate4之一对多关系映射

Posted 2020-06-14

示例：一个部门（Department ）下面有多个用户（User），多个用户对应一个部门

public class Department {
    private Integer id;
    private String name;
    private Set<User> users;
        //getter and setter  
}

public class User{
    private Integer id;
    private String userName;
    private Department department;
        //getter and setter  
}

用XML映射

<hibernate-mapping package="com.shen.hibernate4.entity">
    <class name="Department " table="tb_department ">
        <id name="id">
            <generator class="identity" />
        </id>
        <property name="name" />
       <!--反转：设置从User端加入数据失效,不维护关联关系。注:Hibernate默认inverse="false"为主控方，由主控方负责维护对象的关系联系。-->
        <set name="users" inverse="true">  
            <key column="department_id" />  
            <one-to-many class="User"/>
        </set>  
    </class>
</hibernate-mapping>
 
<hibernate-mapping package="com.shen.hibernate4.entity">
    <class name="User" table="tb_user">
        <id name="id">
            <generator class="identity"/>
        </id>
        <property name="userName" column="user_name"/>
         <!-- 此处需要与Department 端的配置的字段保持一致-->  
        <many-to-one name="department" column="department_id" class="Department " not-null="true"/>
    </class>
</hibernate-mapping>

用@Annotation映射

@Entity
@Table(name = "tb_department")
public class Category {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Integer id;
    private String name;
    
    //mappedBy 值为User中Department类型属性
    @OneToMany(mappedBy = "department")
    private Set<User> users;
    //getter and setter 
}

@Entity
@Table(name = "tb_user")
public class User{

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Integer id;
    private String userName;
    
    @ManyToOne  
    @JoinColumn(name = "department_id", nullable = false)
    private Department department;
        //getter and setter  
}

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