BlogJava-jiadong-随笔分类-HIBERNATEhttp://www.blogjava.net/jiadong/category/25173.htmlzh-cnWed, 29 Aug 2007 14:00:48 GMTWed, 29 Aug 2007 14:00:48 GMT60关于Hibernate中的映射问题http://www.blogjava.net/jiadong/archive/2007/08/27/139765.htmljiadongjiadongMon, 27 Aug 2007 02:10:00 GMThttp://www.blogjava.net/jiadong/archive/2007/08/27/139765.htmlhttp://www.blogjava.net/jiadong/comments/139765.htmlhttp://www.blogjava.net/jiadong/archive/2007/08/27/139765.html#Feedback0http://www.blogjava.net/jiadong/comments/commentRss/139765.htmlhttp://www.blogjava.net/jiadong/services/trackbacks/139765.html
其实呢多对多的关系映射，是在一对多的基础上进行的。
如果现在数据库中有两张表（经典的多对多：student-teacher）
student: studentid(primary key ),studentname
teacher: teacherid(primary key ),teachername
存放其关系的表：stu_tea_relation: studentid,teacherid

因为一对多的映射，几乎上都是通过Set来处理，所以多对多也是如此。首先生成POJO类，然后配置xml文件
其中的 Student.hbm.xml
 1<hibernate-mapping>
 2    <class name="org.jia.Student" table="student">
 3        <id name="studentid" type="integer">
 4            <column name="studentid" />
 5            <generator class="native" />
 6        </id>
 7        <property name="studentname" type="string">
 8            <column name="studentname" not-null="true" />
 9        </property>
10        <set name="teachers" table="stu_tea_relation" inverse="true"
11            cascade="all">
12            <key column="studentid"></key>
13            <many-to-many column="teacherid"
14                class="org.jia.Teacher">
15            </many-to-many>
16        </set>
17    </class>
18</hibernate-mapping>
//name="teacher"是指在Student.java中的那个set对象，以及相应的getter，stter方法的名字
//inverse是说明，是通过谁来管理谁，在此为true，说明是通过老师来选学生
<set name="teachers" table="stu_tea_relation" inverse="true"    cascade="all">
   <key column="studentid"></key>
   <many-to-many column="teacherid"
    class="org.jia.Teacher">
   </many-to-many>
  </set>
同样的Teacher.hbm.xml
<hibernate-mapping>
    <class name="org.jia.Teacher" table="teacher">
        <id name="teacherid" type="integer">
            <column name="teacherid" />
            <generator class="native" />
        </id>
        <property name="teachername" type="string">
            <column name="teachername" not-null="true" />
        </property>
        <set name="students" table="stu_tea_relation" inverse="false"
            cascade="all">
            <key column="teacherid"></key>
            <many-to-many column="studentid"
                class="org.jia.Student">
            </many-to-many>
        </set>
    </class>
</hibernate-mapping>



jiadong 2007-08-27 10:10 发表评论
]]>