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many-to-one lazy relationship in hibernate

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ken.carlino

Post subject: many-to-one lazy relationship in hibernate

Posted: Fri Nov 03, 2006 8:33 pm

Newbie

Joined: Sun Oct 15, 2006 11:20 pm
Posts: 13

Hi,

I have a mapping of 'Agent' like this:

Code:

<class name="com.mycompany.model.Agent"
      table="AGENTS" lazy="true">

      <id name="id" column="AGENT_ID">
         <generator class="native" />
      </id>

      <version name="version" column="version"
         type="java.lang.Integer" />

      <many-to-one name="phone" column="PHONE_ID"
         class="com.mycompany.model.Phone" />

   </class>

I have hibernate sql send to stdout so that I know what is the sql.
// see a sql statement here from hibernate
Agent agent = agentManager.getAgentByName('aName');
// do not see a sql statement here.
Phone phone = agent.getPhone();
[/code]

My question is why I don't see any sql statement when I do 'agent.getPhone()' the relationship is 'lazy', so I expect hibernate will query that only when I do agent.getPhone(), so I don't see that happening.

Can you please help me understand why?

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rajasaur

Post subject:

Posted: Sat Nov 04, 2006 4:36 am

Senior

Joined: Tue Aug 23, 2005 8:52 am
Posts: 181

Try doing a phone.getSomething(). thats the time when Hibernate will actually run the query. When you do a agent.getPhone(), all you are returned is the proxy object which was created when the Agent object was loaded. Only on loading a specific property of Phone will the actual SQL be run.

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ken.carlino

Post subject:

Posted: Sat Nov 04, 2006 2:41 pm

Newbie

Joined: Sun Oct 15, 2006 11:20 pm
Posts: 13

Thanks.

What if I call phone.getId() in another query? Will the phone.getId() generate another query)?

Code:

   Query query = session
            .createQuery(
                  "from AREA as area where  area.country= :country and area.phone.id = :phoneid");
      
      
      List result = query.setString("country", country).setLong("phoneid",
                  phone.getId().longValue()).list();

and do you know which query is better (efficiency wise).

This:

Code:

List result = query.setString("country", country).setLong("phoneid",
                  phone.getId().longValue()).list();

or this:

Code:

List result = query.setString("country", country).setEntity("phone", phone)).list();

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