tm4j-users

[TM4J-users] Hibernate and Tolog

[George T. <geo...@fr...>]

Hello Kal (and Hibernate users)
it's me again :-)

because the mail breaks the lines and the message is not very easily
readable, I am attaching it as plain text also

I don't want to bother you, but I don't know what to do here
I thing the CLASSPATH and the .jar files are all OK.
(the jars are from "tm4j-bin-0.9.8.zip")

When I call the following code:

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);
TologResultsSet rSet = qe.execute ("topic($T)?");


I get from the "qe.execute ("topic($T)?")" the following Exception:



0 [main] ERROR net.sf.hibernate.impl.IteratorImpl - could not get next
result
java.sql.SQLException: Operation not allowed after ResultSet closed
at com.mysql.jdbc.ResultSet.checkClosed(ResultSet.java:3599)
at com.mysql.jdbc.ResultSet.next(ResultSet.java:2464)
at net.sf.hibernate.impl.IteratorImpl.postNext(IteratorImpl.java:63)
at net.sf.hibernate.impl.IteratorImpl.next(IteratorImpl.java:91)
at
uk.co.jezuk.mango.iterators.TransformingIterator.next(TransformingIterator.j
ava:22)
at org.tm4j.tologx.predicates.TopicPredicate.matches(TopicPredicate.java:57)
at org.tm4j.tologx.predicates.PredicateBase.matches(PredicateBase.java:57)
at org.tm4j.tologx.parser.ClauseList.executePredicate(ClauseList.java:124)
at org.tm4j.tologx.parser.ClauseList.execute(ClauseList.java:44)
at org.tm4j.tologx.parser.TologQuery.execute(TologQuery.java:108)
at
org.tm4j.tologx.memory.PreparedQueryImpl.execute(PreparedQueryImpl.java:49)
at
org.tm4j.tologx.memory.QueryEvaluatorImpl.execute(QueryEvaluatorImpl.java:16
7)
at etm.Test.main(Test.java:52)
net.sf.hibernate.LazyInitializationException: Hibernate lazy instantiation
problem
at net.sf.hibernate.impl.IteratorImpl.next(IteratorImpl.java:97)
at
uk.co.jezuk.mango.iterators.TransformingIterator.next(TransformingIterator.j
ava:22)
at org.tm4j.tologx.predicates.TopicPredicate.matches(TopicPredicate.java:57)
at org.tm4j.tologx.predicates.PredicateBase.matches(PredicateBase.java:57)
at org.tm4j.tologx.parser.ClauseList.executePredicate(ClauseList.java:124)
at org.tm4j.tologx.parser.ClauseList.execute(ClauseList.java:44)
at org.tm4j.tologx.parser.TologQuery.execute(TologQuery.java:108)
at
org.tm4j.tologx.memory.PreparedQueryImpl.execute(PreparedQueryImpl.java:49)
at
org.tm4j.tologx.memory.QueryEvaluatorImpl.execute(QueryEvaluatorImpl.java:16
7)
at etm.Test.main(Test.java:52)
Caused by: java.sql.SQLException: Operation not allowed after ResultSet
closed
at com.mysql.jdbc.ResultSet.checkClosed(ResultSet.java:3599)
at com.mysql.jdbc.ResultSet.next(ResultSet.java:2464)
at net.sf.hibernate.impl.IteratorImpl.postNext(IteratorImpl.java:63)
at net.sf.hibernate.impl.IteratorImpl.next(IteratorImpl.java:91)
... 9 more


the
"net.sf.hibernate.impl.IteratorImpl.next(IteratorImpl.java:91)" belongs
in "hibernate2.jar"

the
"uk.co.jezuk.mango.iterators.TransformingIterator.next(TransformingIterator.
java:22)"
belongs in "mango.jar"

the
"org.tm4j.tologx.predicates.TopicPredicate.matches(TopicPredicate.java:57)"

is the:
addResultsRow(ret, new Object[] {it.next()});

in the:

public VariableSet matches(List params) throws TologProcessingException {
    VariableSet ret = new VariableSet();
    initialiseResultsSet(ret);
    Object p = params.get(0);
    if (p instanceof Variable) {
        Iterator it = getTopicMap().getTopicsIterator();
        while (it.hasNext()) {
            addResultsRow(ret, new Object[] {it.next()});
        }
    } else if (p instanceof Topic) {
        addResultsRow(ret, new Object[] {p});
    }
    return ret;
}

inside the TopicPredicate.java


I understend that the "it.next()" gets:
"java.sql.SQLException: Oeration not allowed after ResultSet closed"

I suppose the "getTopicMap().getTopicsIterator()" (in the case of
Hibernate) is served by:
"org.tm4j.topicmap.hibernate.TopicMapImpl"


public Iterator getTopicsIterator() {
    if (m_provider.isTransactionOpen()) {
        return getTopicsIterator(m_provider.getOpenTransaction());
    } else {
        ProviderTransaction txn = m_provider.openTransaction();
        Iterator ret = getTopicsIterator(txn);
        txn.rollback();
        return ret;
    }
}

private Iterator getTopicsIterator(ProviderTransaction txn) {
    TopicMapDataObject tdo = (TopicMapDataObject) load(txn);
    Iterator rawIt = iterate(txn, "select topic from topic in class
org.tm4j.topicmap.hibernate.TopicDataObject where topic.topicMap = ?",
tdo, Hibernate.entity(TopicMapDataObject.class));
    return new TransformingIterator(rawIt, getWrapper());
}

(The Topic Map works and it is editable, only the Tolog is that is not
working)

Is it possible that the "Iterator it = getTopicMap().getTopicsIterator();"
closes the ResultSet (accidentally) and then return the Iterator?

Is anybody uses the combination of Hibernate and Tolog without this problem?

Thank you again
George Tryfon




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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.