hibernate 一对多关联

2023-11-01 18:01:04

1.映射文件

一

<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC
  "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
  "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping package="one2many">
  <class name="Tuser" table="t_user">
    <id name="id">
      <generator class="native"/>
    </id>
    <property name="name"/>
    <set name="addresses" lazy="true"    cascade="all" >
      <key column="user_id"    not-null="true"/>
      <one-to-many class="Taddress" />
    </set>
  </class>


</hibernate-mapping>

多

<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC
  "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
  "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping package="one2many">
  <class name="Taddress" table="t_address">
    <id name="cid">
      <generator class="native"/>
    </id>
    <property name="tel" />
    <property name="zipcode"/>
  </class>


</hibernate-mapping>

测试代码：

  public void testInsert(){
    Transaction tc = null;
    try{
      tc = session.beginTransaction();
      Tuser user = new Tuser();
      user.setName("xiaozhao2");

      Set adds = new HashSet();
      Taddress add1 = new Taddress();
      add1.setTel("123");
      add1.setZipcode("897");


      Taddress add2 = new Taddress();
      add2.setTel("123");
      add2.setZipcode("897");

      adds.add(add1);
      adds.add(add2);
      user.setAddresses(adds);

      session.save(user);
      tc.commit();
    }catch(HibernateException e){
      tc.rollback();
      e.printStackTrace();
    }

  }

生成的sql

Hibernate: insert into t_user (name, id) values (?, ?)
Hibernate: insert into t_address (tel, zipcode, user_id, cid) values (?, ?, ?, ?)
Hibernate: insert into t_address (tel, zipcode, user_id, cid) values (?, ?, ?, ?)
Hibernate: update t_address set user_id=? where cid=?
Hibernate: update t_address set user_id=? where cid=?

注意：并没有报错，《深入浅出Hibernate》说是会报错的，

将t_address 表的user_id 字段设置为非空了。

书上说会报错的。我怎么没有报错呢

一对多双向关联

一的一方：

<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC
  "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
  "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping package="one2many">
  <class name="Tuser" table="t_user">
    <id name="id">
      <generator class="native"/>
    </id>
    <property name="name"/>
    <set name="addresses" lazy="true"    cascade="all" inverse="true" >
      <key column="user_id" />
      <one-to-many class="Taddress" />
    </set>
  </class>


</hibernate-mapping>

多的一方：

<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC
  "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
  "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping package="one2many">
  <class name="Taddress" table="t_address">
    <id name="cid">
      <generator class="native"/>
    </id>
    <property name="tel" />
    <property name="zipcode"/>

    <many-to-one name="user" column="user_id"/>
  </class>


</hibernate-mapping>

测试代码：

发出sql:

1.如果我把<key column="user_id" /> 修改为<key column="user_id" not-null="true"/>

这时候会把错。为什么这时候才报错呢？

发出的sql 都一样。个人认为：可能是inverse的用法

本文转自 randy_shandong 51CTO博客，原文链接：http://blog.51cto.com/dba10g/246180，如需转载请自行联系原作者

码农公寓

相关文章