hibernate的数据关联映射

数据关联映射分为：一对多、多对一，一对一，多对多。

cascade属性
• save-update：在执行保存和修改是进行级联操作
• delete：在执行删除时进行级联操作
• all：在所有情况下进行级联操作
• none：不进行级联操作（默认）

抓取策略

一对多、多对一

一对多、多对一持久化类设计
// User类
public class User { 

private int id;
private String name;
private int age;
private Set<Address> addressSet; 

//get set method
}

//Address类
public class Address { 

private int id;
private String address;
private int tel;
private User user; 

//get set method
}

address.hbm.xml
<hibernate-mapping package="com.hussion.pojo">
    <class name="Address" table="t_address">
        <id name="id">
          <generator class="native"/>
        </id>
        <property name="address"></property>
        <property name="tel"></property>
        <many-to-one name="user" class="User" column="userid"/>
    </class>
</hibernate-mapping>

user.hbm.xml
<hibernate-mapping package="com.hussion.pojo">
    <class name="User" table="t_user">
        <id name="id" column="id">
          <generator class="native"></generator>
        </id>
        <property name="name" column="name"></property>
        <property name="age" column="age"></property> 

        <!--inverse="true"放弃关系维护-->
        <set name="addressSet" inverse="true">
          <key column="userid"/>
          <one-to-many class="Address"/>
        </set>
    </class>
</hibernate-mapping>

一对一

持久化类设计
public class Person { 

private int id;
private String userName;
private Card card; 

//get set Method
} 

public class Card { 

private int id;
private String cardNum;
private Person person; 

//get set Method
}

person.hbm.xml
<hibernate-mapping package="com.hussion.pojo">
    <class name="Person" table="t_person">
        <id name="id">
          <generator class="native"></generator>
        </id>
         <property name="userName"></property>
          <one-to-one name="card" class="Card" cascade="delete"/>
    </class>
</hibernate-mapping>

多对多

ublic class Teacher { 

private int id;
private String name;
private Set<Student> student; 

//get set method
}
public class Student { 

private int id;
private String name;
private Set<Teacher> teacher; 

//get set method
}

teacher.hbm.xml
<hibernate-mapping package="com.hussion.pojo">
    <class name="Teacher" table="t_teacher">
        <id name="id" column="id">
          <generator class="native"></generator>
        </id>
          <property name="name"></property>
        <set name="student" table="t_student_techer">
          <key column="teacherid"/>
          <many-to-many class=“Student” column=“studentid”/>
        </set>
    </class>
</hibernate-mapping>

student.hbm.xml
<hibernate-mapping package="com.hussion.pojo">
    <class name="Student" table="t_student">
        <id name="id" column="id">
          <generator class="native"></generator>
        </id>
        <property name="name"></property>
        <set name="teacher" table="t_student_techer">
            <key column="studentid"/>
            <many-to-many class="Teacher" column="teacherid />
        </set>
    </class>
</hibernate-mapping>

多对多一方要放弃关系维护
<set name="student" table="t_teacher_student"  inverse="true">

排序
<many-to-many class="Student" column="s_id"  order-by="id asc,name desc"></many-to-many>

延迟加载关闭 ： lazy="false"

hibernate的数据关联映射