Re: [TM4J-users] Hibernate and Tolog

[Kal A. <ka...@te...>]

Hi George,

I think that it is exactly the problem that you suspect. When the 
transaction is closed, the results set is also closed. What you will 
need to do is to wrap your use of the tolog results in its own 
transaction. So you will need  a few extra calls in your sample code:
George Tryfon wrote:

>Properties props = new Properties ();
>
>props.setProperty
>("hibernate.dialect","net.sf.hibernate.dialect.MySQLDialect");
>props.setProperty
>("hibernate.connection.driver_class","com.mysql.jdbc.Driver");
>props.setProperty ("hibernate.connection.url","jdbc:mysql://localhost/etm");
>props.setProperty ("hibernate.connection.username", "root");
>props.setProperty ("hibernate.connection.password", "123");
>
>TopicMapProviderFactory tmpf = new TopicMapProviderFactoryImpl();
>TopicMapProvider provider = tmpf.newTopicMapProvider(props);
>
>Map mapFeatures = new HashMap ();
>TMAPITopicMapSystemImpl tmApiSystImpl = new TMAPITopicMapSystemImpl
>(tmpf.getClass().getName(), props, mapFeatures);
>
>Locator loc = provider.getLocatorFactory().createLocator ("URI", tmName);
>org.tm4j.topicmap.TopicMap tm = provider.getTopicMap (loc);
>
>QueryEvaluator qe = QueryEvaluatorFactory.newQueryEvaluator (tm);
>  
>
ProviderTransaction txn = provider.openTransaction();

>TologResultsSet rSet = qe.execute ("topic($T)?");
>
>
>  
>
// Do stuff with rSet

txn.abort();

What *should* happen is that the underlying Hibernate topic map provider 
code should use the transaction you explictly opened for all lookup 
operations involved in processing the tolog query and it should not try 
and close the transaction (because it did not open it).

I guess this is really a workaround for an underlying problem which is 
that the Tolog query implementation is not doing the transaction 
wrapping itself. Although the real issue at the heart of this is that 
the tolog implementation for Hibernate should be making more use of SQL 
or Hibernate's query language instead of translating the query into 
operations against the TM4J API. Neither of those changes are going to 
happen quickly to the code base (unless someone wants to volunteer!), so 
in the meantime I recommend that you do this explicit wrapping in your 
code. In a way it is clearer anyway - even if it does require a bit more 
typing!

Hope this helps**,

Kal

** Disclaimer - I haven't actually tried this, but it is my best guess, 
and its the way that I worked around other issues with iterators 
returned by the Hibernate implementation.