以多对一关系归档的版本导致对象引用未保存的瞬态实例

Question

i have a class like this :

public class User(){
        private String name;
        private Integer version ; 

        //getter & setter 
}

and the hibernate mapping file is :

<?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>
    <class name="org.model.User" table="User">
        <id name="id" column="Id" type="java.lang.Integer">
            <generator class="sequence" >
                <param name="sequence">SEQ_User</param>   
            </generator>
        </id>
        <version name="version" column="version" type="Integer" />
        <property name="name"    column="Name"   type="string" not-null="true"  />
 </class>

</hibernate-mapping>

when i use as a many-to-one relation like this :

public class UserDetail(){
        private String tel;
        private User    user;
   // getter & setter 
    }

and this is UserDetail.hbm.xml file :

<?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>
    <class name="org.model.UserDetail" table="User_Detail">
        <id name="id" column="Id" type="java.lang.Integer">
            <generator class="sequence" >
                <param name="sequence">SEQ_User_Detail</param>   
            </generator>
        </id>

        <property name="tel"    column="tel"   type="string" not-null="true"  />
        <many-to-one name="user"            column="user_Id"        entity-name="org.model.User" />

 </class>

</hibernate-mapping>

when i want to save the UserDetail take this exception :

object references an unsaved transient instance - save the transient instance before flushing

i save the UserDetail object in the way below :

@Override
    public void add(UserDetail entity) {
        Session session = getSession();
        session.save(entity);
    }

and i set User in the UserDetail like this :

entity.setUser(new User(1));

i just know the UserId and never load the user object.

Answer 1

Although you haven't added the code for UserDetails and the persistence logic, I suppose you have a @ManyToOne association to a User in UserDetails .

If you have a User and a UserDetails that you want to persist, you have to call persist() on both entities. Unless you have a parent-side association in User , you cannot use cascading since cascade makes sense only from parent to children but not vice versa .

This has nothing to do with concurrency or versioning as you initially suspected.

You said that:

I don't have any problem when i remove version field

That could be explained if you set an id to a transient User instance and you try to call persist() :

User user = new User();
user.setId(1L);
user.setVersion(0);
session.persist(user);

Because you have a sequence identifier generator, it is Hibernate that should assign identifiers. Also, the version property should never be assigned manually. If you have a detached entity, you need to call merge instead of persist .

Update

According to your update and the new source code, I can't find any particular issue. However, you should know that the Session might have been opened before and maybe there are other entities that you added previously to creating the User entity. It's only during the flush that entity state transitions are propagated to the DB.

Answer 2

在我调试后，如果我们将版本字段 Null 放在 User 中，我会收到异常，但是当我将其设置为零时，问题就解决了