Get Hibernate Entity instance from id column in SQLQuery result

Question

I have (non-Hibernated) database tables that contain ids for Hibernate entities. I can query them (using createSQLQuery), which gives me the ids, from which I can then load the entities.

I'd like to do that in one step, and I think I can do that with addEntity, but I am not sure how exactly. (Hibernate's documentation web site is down. Again.) I can use addEntity when all the columns for the entity table are present, but I have only the id now.

This complains about the missing columns:

return (List<MyEntity>) session.createSQLQuery(
            "select entity_id from the_table where foreign_key_value = ?")
            .addEntity("entity_id", MyEntity.class)
            .setLong(0, foreignKey).list();

Answer 1

i would use a join

select * 
from entity_table 
where entity_id = (select entity_id
                   from non_hibernate_table
                   where id = ?)

Answer 2

For oracle dialect. If u have problem with mapping database column type to java data type u can set it manually like that: .addScalar("integerFieldName", Hibernate.INTEGER)

public class LookupCodeName
{
    private String code;
    private String name;

 /*... getter-setters ... */
}

public class someBL {

public List<LookupCodeName> returnSomeEntity() {
      SQLQuery sqlQuery =  (SQLQuery)((HibernateSession)em).getHibernateSession()
       .createSQLQuery( "SELECT st.name as name, st.code as code FROM someTable st")
       .addScalar("code")
       .addScalar("name")
.setResultTransformer(Transformers.aliasToBean(LookupCodeName.class));
    }
return (List<LookupCodeName>)sqlQuery.list();
}

Answer 3

I think you want something like:

session.createSQLQuery("select {entity.*} from entity_table {entity} where ....")
  .addEntity("entity", Entity.class).(bind-parameters).list();

Hibernate will expand "{entity.*}" to be the relevant columns from entity_table.

Although if you already have the IDs, you can simply use session.load() to convert those to actual instances (well, lazy-load proxies).