hibernate 多对多操作删除

hibernate 多对多操作

关键字: hibernate 多对多操作

多对多的两种映射形式：
一。映射多对多关系
老师Teacher 与 课程Course 是一个多对多的关系，XMl配置如下。
三个表的表结构
1. tbl_course.sql
    create table "SCOTT"."TBL_COURSE"(
        "ID" CHAR(32) not null,
       "NAME" VARCHAR2(20) not null,
        constraint "SYS_C005315" primary key ("ID")
    );
2. tbl_teacher.sql
    create table "SCOTT"."TBL_TEACHER"(
        "ID" CHAR(32) not null,
       "NAME" VARCHAR2(20) not null,
        constraint "SYS_C005313" primary key ("ID")
    );
3.tbl_teacher_course.sql
  create table "SCOTT"."TBL_TEACHER_COURSE"(
        "TID" CHAR(32),
       "CID" CHAR(32)
    );

Teacher.hbm.xml
<hibernate-mapping>
    <class name="mapping.Teacher" table="teacher" schema="dbo" catalog="Student">
        <id name="id" type="string">
            <column name="ID" length="32" />
            <generator class="uuid" />
        </id>
        <property name="name" type="string">
            <column name="Name" length="50" not-null="true" />
        </property>
        <set access="property" name="courses" lazy="true" inverse="true" 
             cascade="save-update"  batch-size="10" fetch="select" 
             table="teacher_course"> 
             <key column="TID" />
             <many-to-many class="mapping.Course1" column="CID" /> 
         </set> 
    </class>
</hibernate-mapping>

COURSE.hbm.xml
<hibernate-mapping>
    <class name="mapping.Course" table="course" schema="dbo" catalog="Student">
        <id name="id" type="string">
            <column name="ID" length="32" />
            <generator class="uuid" />
        </id>
        <property name="cname" type="string">
            <column name="cname" length="50" />
        </property>
        <set access="property" name="teachers" lazy="true" inverse="false" 
             cascade="save-update"  batch-size="10" fetch="select"  table="teacher_course"> 
             <key column="CID" />
             <many-to-many class="mapping.Teacher" column="TID" /> 
         </set>
    </class>
</hibernate-mapping>


1. 如果cascade 不管主控方设置还是被控方设置成all或delete，级联删除时，两端以及中间表的记录都会被删除，通常这样的需要是很少的。

2. 只想删除某一端的记录以及中间的表的关联信息。 这种需求通常是很常见的。这个时候cascade的设置是除与delete有关的任何级联约束。以下是删除心得：

2.1 通过主控方来删除
/** 
* 多对多 主控方删除(可以删除中间表记录) 
*/   
Session session = HibernateSessionFactory.getSession(); 
session.beginTransaction();
   
String cid = "2c2880d12041c65f012041c665180001";
Course course1 = (Course) session.get(Course.class , cid); 
session.delete(course1);
session.getTransaction().commit(); 
session.close();

2.2 通过被控方来删除
/** 
* 多对多 被控方删除(无法删除中间表记录) 
*/   
String id = "402881ee175a2e7c01175a2e7ead0003" ; 
Session session = HibernateSessionFactory.getSession(); 
session.beginTransaction(); 
Teacher t1 = (Teacher) session.get(Teacher.class , id); 
session.delete(t1); 
session.getTransaction().commit(); 
session.close(); 

/** 
* 多对多 被控方删除(可以删除中间表记录)  
*/   
String id = "402881ee175a2e7c01175a2e7ead0003" ; 
Session session = HibernateSessionFactory.getSession(); 
session.beginTransaction(); 
Teacher t1 = (Teacher) session.get(Teacher.class , id);

Set<Course> cs = t1.getCourses(); 
for  (Course c : cs) { 
    c.getTeachers().remove(t1); 
} 
session.delete(t1); 
session.getTransaction().commit(); 
session.close();  


二。映射为两个一对多关系
三个表结构如下：
CREATE TABLE [dbo].[student] (
[id] [bigint] IDENTITY (1, 1) NOT NULL ,
[sno] [varchar] (50) COLLATE Chinese_PRC_CI_AS NOT NULL ,
[sname] [varchar] (50) COLLATE Chinese_PRC_CI_AS NOT NULL ,
[gender] [varchar] (50) COLLATE Chinese_PRC_CI_AS NULL
) ON [PRIMARY]

CREATE TABLE [dbo].[score] (
[id] [bigint] IDENTITY (1, 1) NOT NULL ,
[cid] [bigint] NULL ,
[sid] [bigint] NULL ,
[scgrade] [float] NOT NULL
) ON [PRIMARY]

CREATE TABLE [dbo].[course] (
[id] [bigint] IDENTITY (1, 1) NOT NULL ,
[cno] [varchar] (50) COLLATE Chinese_PRC_CI_AS NOT NULL ,
[cname] [varchar] (50) COLLATE Chinese_PRC_CI_AS NOT NULL
) ON [PRIMARY]

Student.hbm.xml
<hibernate-mapping>
    <class name="mapping.Student" table="student" schema="dbo" catalog="Student">
        <id name="id" type="java.lang.Long">
            <column name="id" />
            <generator class="identity" />
        </id>
        <set name="scores" cascade="all" inverse="true"  table="score" >
            <key>
                <column name="sid" not-null="true"  />
            </key>
            <one-to-many class="mapping.Score" />
        </set>
    </class>
</hibernate-mapping>

Score.hbm.xml
<hibernate-mapping>
    <class name="mapping.Score" table="score" schema="dbo" catalog="Student">
        <id name="id" type="java.lang.Long">
            <column name="id" />
            <generator class="identity" />
        </id>

        <many-to-one name="course" class="mapping.Course" >
            <column name="cid"  />
        </many-to-one>
        <many-to-one name="student" class="mapping.Student" >
            <column name="sid" />
        </many-to-one>
    </class>
</hibernate-mapping>


Course.hbm.xml
<hibernate-mapping>
    <class name="mapping.Course" table="course" schema="dbo" catalog="Student">
        <id name="id" type="java.lang.Long">
            <column name="id" />
            <generator class="identity" />
        </id>
        <set name="scores" cascade="all" inverse="true"  table="score">
            <key>
                <column name="cid" not-null="true" />
            </key>
            <one-to-many class="mapping.Score" />
        </set>
    </class>
</hibernate-mapping>

/** 
* 一对多 被控方删除(可以删除中间表记录)   学生
*/ 
Long lid = Long.valueOf("19");
Session session = HibernateSessionFactory.getSession();
session.beginTransaction();
Student student = (Student)session.get(Student.class, lid);
session.delete(student); 
session.getTransaction().commit();
session.close();

/** 
* 一对多 被控方删除(可以删除中间表记录)   课程
*/
Long lid = Long.valueOf("19");
Session session = HibernateSessionFactory.getSession();
session.beginTransaction();
Course course = (Course)session.get(Course.class, lid);
session.delete(course); 
session.getTransaction().commit();
session.close();

另外从网上收集了一些资料，进行了整理， 附件内容包括一对一，一对多，多对多类型映射及详细说明。希望对学习hibernate的朋友有所帮助。