hibernate使用小异常

快速解决遇到hibernate的小问题

Nov 7

 1.id 设置native自增报错？native需要数据库设置自增

id使用native自增，跑测试用例，抛异常

org.hibernate.HibernateException: The database returned no natively generated identity value

 

 2.单向一对多，抛出异常

User  表对应多个Address，配置User单项一对多，测试用例报错，详情如下：

xml 代码

<class name="User" table="user">

    <id name="userId" type="integer" column="user_id">
         <generator class="native" />
    id>

    <bag name="userAddress" lazy="true" >
        <key column="user_id" >key>
        <one-to-many class="UserAddress">one-to-many>
    bag>

class>

报错：UserAddress未保存 

java 代码

org.hibernate.ObjectNotFoundException: No row with the given identifier exists: [com.hibernate.bean.user.UserAddress#123]

原因：没有设置级联更新，添加cascase='true'，修改如下：

xml 代码

<bag name="userAddress" lazy="true" cascade="all"><!---->
    <key column="user_id" >key>
    <one-to-many class="UserAddress">one-to-many>
bag>

  

3.update一对多对象，报错：no session or session is close

UserAddress设置lazy=true

xml 代码

<bag name="userAddress" lazy="true" cascade="all"><!---->
    <key column="user_id" >key>
    <one-to-many class="UserAddress">one-to-many>
bag>

将UserAddress的list 赋值给 user, 保存user后，再次查询保存后User , 报错 no session or session is close

java 代码

public boolean addUserAddress(int userid, UserAddress userAddress) {

    User user = (User) dao.findById(User.class, 123);

    List list = new ArrayList();
    list.add(userAddress);

    user.setUserAddress(list);

    dao.update(user);
    User user2 = (User) dao.findById(User.class, 123);
}

java 代码

org.hibernate.LazyInitializationException: failed to lazily initialize a collection of role: com.hibernate.bean.user.User.userAddress, no session or session was closed

 看到 no session or session was close ，立即应该想到方法没有事务处理，延时加载UserAddress，必须在事务里面，不然怎么加载呢？ 添加事务，以spring为例：

java 代码

@Transactional
public boolean addUserAddress(int userid, UserAddress userAddress) {
}

 

评论

1 楼 yuan_2004 2008-10-25  

一对多，查询．cascade="all"　就可以了．多谢