Creating a new object instance in hibernate using a sql query

I am attempting to create an object in hibernate using a query, which will then be saved back to the table representing the class.

Excerpt from hbm.xml file:

<class name="MyClass" table="MY_TABLE">
<id column="ID" name="ID">
   <generator class="sequence">
    <param name="sequence">MY_SEQ</param>
   </generator>
</id>
  <property column="VAL" name="val" type="string"/>
</class>

<sql-query name="myQuery">
  <return class="MyClass"/>
  SELECT MY_SEQ.nextval ID, 'something' VAL from DUAL
</sql-query>

Code snippet from test case:

MyClass myClass = (MyClass) session.getNamedQuery("myQuery").list().get(0);
Transaction t = session.beginTransaction();
session.save(myClass);
t.commit();

My aim is that there should now be a new record in table MY_TABLE, but the insert does not occur, I assume that this is due the fact that Hibernate does not know that the instance has not been persisted in the db.

I have tried changing the query to read:

SELECT NULL ID, 'something' VAL from DUAL

But this results in Hibernate not instantiating an object.

So how can i create a new object instance from a query that is not associated开发者_如何学Python with a persisted instance of the class and use this to create a persisted instance?

Update: I tested the approach suggested below and I couldn't get it working for this particular scenario, Hibernate expects you to select columns for all attributes while we definitely don't want the id. However, using a ResultTransformer did work:

16.1.5. Returning non-managed entities

It is possible to apply a ResultTransformer to native SQL queries, allowing it to return non-managed entities.

sess.createSQLQuery("SELECT NAME, BIRTHDATE FROM CATS")
        .setResultTransformer(Transformers.aliasToBean(CatDTO.class))

This query specified:

• the SQL query string
• a result transformer

The above query will return a list of CatDTO which has been instantiated and injected the values of NAME and BIRTHNAME into its corresponding properties or fields.

The documentation mentions returning non-managed entities but it also work with an entity (there is no reason it wouldn't work) and I could persist the transient entity successfully.

See also

• Hibernate 3.2: Transformers for HQL and SQL

I'm leaving the initial answer for clarity sake.

Maybe the following will help:

But I don't think you should set the ID if you want to save it and want Hibernate to perform an insert.