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Apache Jena SPARQL query will not abort

I'm having a problem in my Java application where Apache Jena will never stop a SPARQL query until it's finished, even if I explicitly tell it to stop. Here's the code that gets called to run a query:
try {
Model union = null;
union = ModelFactory.createOntologyModel(OntModelSpec.OWL_MEM_RULE_INF);
if (ontologies != null)
for (OntModel om : ontologies)
union = ModelFactory.createUnion(union, om);
Reasoner reasoner = ReasonerRegistry.getOWLReasoner();
reasoner = reasoner.bindSchema(union);
InfModel infmodel = ModelFactory.createInfModel(reasoner, triples);
query_running = true;
Query query = QueryFactory.create(query_string);
query_execution = QueryExecutionFactory.create(query, infmodel);
ResultSet rs = query_execution.execSelect();
for ( ; rs.hasNext(); ) {
// do stuff with results
}
} catch (Exception e) {}
finally {
stopQuery();
}
stopQuery() gets called at the end, but the method is also called when the user hits a "cancel" button. Here's what that method looks like:
public void stopQuery() {
try {
if (query_execution != null) {
//query_execution.close();
query_execution.abort();
query_execution = null;
System.out.println("STOPPED");
}
} catch (Exception e) { e.printStackTrace(); }
query_running = false;
}
When the cancel button is hit while a query is running (10+ minutes on a relatively small dataset...?), the method gets called, but the query continues to run in the background. I know it's still running because I can see the application in task manager taking up 30%+ CPU until the query presumably completes. I've tried .abort(), .close(), and both at the same time, but I cannot figure out how to stop the query mid-execution. I've even tried wrapping the query code in a separate thread, but that doesn't work either. It makes sense that threading wouldn't solve the problem because the thread needs to see the interrupt request, but the code is freezing on a particular line. The code seems to freeze on rs.hasNext(), but not the first check. It will run quickly with the first x results of the ResultSet (which are likely explicit statements it finds easily), but then it will seem to freeze for a long while after that, likely searching for implicit results with the reasoner. How can I force the query to stop? I don't want to use a timeout -- I want the user to have the option to stop the query or let it play out. This problem is not specific to any one query or dataset.
Thanks.

Result Set closes automatically

I have a problem with my music bot for Discord.
I want to send an embed message when a track ist started, but the ResultSet always closes.
So it can't pass the if-query.
Here is my code (class "TrackScheduler"):
try {
file = new URL("https://img.youtube.com/vi/" + videoID + "/hqdefault.jpg").openStream();
builder.setImage("attachment://thumbnail.png");
System.out.println("4");
ResultSet set = LiteSQL.onQuery("SELECT * FROM musicchannel WHERE guildid = " + guildid);
try {
System.out.println("3");
if(set.next()) {
long channelid = set.getLong("channelid");
TextChannel channel;
System.out.println("2");
if((channel = guild.getTextChannelById(channelid)) != null) {
System.out.println("1");
channel.sendTyping().queue();
channel.sendFile(file, "thumbnail.png").embed(builder.build()).queue();
}
}
}
catch (SQLException e) {
e.printStackTrace();
}
}
catch (IOException e) {
e.printStackTrace();
}
}
My LiteSQL.onQuery (class "LiteSQL"):
private static Connection c;
private static Statement s;
public static ResultSet onQuery(String sql) {
try {
return s.executeQuery(sql);
}
catch(SQLException e) {
e.printStackTrace();
}
return null;
}
Here is the error:
ava.sql.SQLException: ResultSet closed
at org.sqlite.core.CoreResultSet.checkOpen(CoreResultSet.java:76)
at org.sqlite.jdbc3.JDBC3ResultSet.findColumn(JDBC3ResultSet.java:39)
at org.sqlite.jdbc3.JDBC3ResultSet.getLong(JDBC3ResultSet.java:423)
at de.nameddaniel.bot.musik.TrackScheduler.onTrackStart(TrackScheduler.java:79)
at com.sedmelluq.discord.lavaplayer.player.event.AudioEventAdapter.onEvent(AudioEventAdapter.java:72)
at com.sedmelluq.discord.lavaplayer.player.DefaultAudioPlayer.dispatchEvent(DefaultAudioPlayer.java:368)
at com.sedmelluq.discord.lavaplayer.player.DefaultAudioPlayer.startTrack(DefaultAudioPlayer.java:117)
at com.sedmelluq.discord.lavaplayer.player.DefaultAudioPlayer.playTrack(DefaultAudioPlayer.java:80)
at de.nameddaniel.bot.musik.AudioLoadResult.trackLoaded(AudioLoadResult.java:20)
at com.sedmelluq.discord.lavaplayer.player.DefaultAudioPlayerManager.checkSourcesForItemOnce(DefaultAudioPlayerManager.java:443)
at com.sedmelluq.discord.lavaplayer.player.DefaultAudioPlayerManager.checkSourcesForItem(DefaultAudioPlayerManager.java:419)
at com.sedmelluq.discord.lavaplayer.player.DefaultAudioPlayerManager.lambda$createItemLoader$0(DefaultAudioPlayerManager.java:218)
at java.util.concurrent.FutureTask.run(Unknown Source)
at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
at java.lang.Thread.run(Unknown Source)
I'm new here, so if there is any missing information, please tell me.
As well, I'm sorry for the bad formatting.
Greetings, Daniel :)

tl;dr
Do not use static on your Statement and Connection fields.
Details
This code has a security leak. Look up SQL injection. The basic gist is: Statement is almost entirely useless. You want PreparedStatement, and you want your SQL queries to be solely string literals. Don't, ever, 'make the query string' by concatenating user input in. The Query string should be, say, SELECT * FROM musicchannel WHERE guildid = ? (yes, with a literal question mark in the string), then use the setInt method of PreparedStatement to set the guild id. Or better yet, as the JDBC API is not really designed for consumption like this, use something like JDBI.
This is bad exception handling. If you don't know what to do, the right 'I dont know' catch block is throw new RuntimeException("Uncaught", e); and not e.printStackTrace();. Better yet, have these methods just throw SQLException; methods that obviously do DB things should be throwing that. Note that your main method can (and should) be declared to throw Exception.
Connection, PreparedStatement, and ResultSets are all resources and need to be opened via try-with-resources. Not doing so means your app has a leak and will break something if it runs long enough. For DB code, the DB will eventually run out of connections and become entirely inaccessible until you close the java app. That's why you need try-with-resources.
You have a single Statement and Connection (the fields are static). Presumably your discord bot can receive more than one message, so if you try to send more than one, the system goes down in flames. Don't use 'static' here. The code you pasted does not itself contain anything that would close your ResultSet, but by redesigning away from static the problem is likely to go away by itself.

(Apart from the other answer, which is actually all very good suggestions and you should follow) I presume the following is the problem:
return s.executeQuery(sql);
I don't think that will work if it's a static and is being used multiple times by other objects. It will be cleaned up eventually. Rather than doing that there, you should be returning just an object with the data that you need. Look up the DAO class pattern.

clearing batch preparedstatements

I have a java application which read files and writes to oracle db row by row.
We have come across a strange error during batch insert which does not occur during sequential insert. The error is strange because it occurs only with IBM JDK7 on AIX platform and I get this error on different rows every time. My code looks like below:
prpst = conn.prepareStatement(query);
while ((line = bf.readLine()) != null) {
numLine++;
batchInsert(prpst, line);
//onebyoneInsert(prpst, line);
}
private static void batchInsert(PreparedStatement prpst, String line) throws IOException, SQLException {
prpst.setString(1, "1");
prpst.setInt(2, numLine);
prpst.setString(3, line);
prpst.setString(4, "1");
prpst.setInt(5, 1);
prpst.addBatch();
if (++batchedLines == 200) {
prpst.executeBatch();
batchedLines = 0;
prpst.clearBatch();
}
}
private static void onebyoneInsert(PreparedStatement prpst, String line) throws Exception{
int batchedLines = 0;
prpst.setString(1, "1");
prpst.setInt(2, numLine);
prpst.setString(3, line);
prpst.setString(4, "1");
prpst.setInt(5, 1);
prpst.executeUpdate();
}
I get this error during batch insert mode :
java.sql.BatchUpdateException: ORA-01461: can bind a LONG value only for insert into a LONG column
at oracle.jdbc.driver.OraclePreparedStatement.executeBatch(OraclePreparedStatement.java:10345)
I already know why this Ora error occurs but this is not my case. I am nearly sure that I am not setting some large data to a smaller column. May be I am hitting some bugs in IBM jdk7 but could not prove that.
My question if there is a way that I can avoid this problem ? One by one insert is not an option because we have big files and it takes too much time.

Try with
prpst.setInt(5,new Integer(1))
What is the type of variable "numLine"?
Can you share type of columns corresponding to the fields you set in PreparedStatement?
Try once by processing with "onebyoneInsert". Share the output for this case. It might help identifying root cause.
Also print value of "numLine" to console.

Creating multiple transactions in a single hibernate session

I have created a Quartz Job which runs in background in my JBoss server and is responsible for updating some statistical data at regular interval (coupled with some database flags)
To load and persist the I am using Hibernate 4. Everything works fine except one hick up.
The entire thread i.e. Job is wrapped in a Single transaction which over the period of time (as the amount of data increases) becomes huge and worry some. I am trying to break this single large transaction into multiple small ones, such that each transaction process only a sub group of data.
Problem: I tried very lamely to wrap a code into a loop and start/end transaction at start/end of the loop. As I expected it didn't work. I have been looking around various forums to figure out a solution but have not come across anything that indicates managing multiple transaction in a single session (where in only 1 transaction will be active at a time).
I am relatively new to hibernate and would appreciate any help that points me to a direction on achieving this.
Update: Adding code demonstrate what I am trying to achieve and mean when I say breaking into multiple transaction. And stack trace when this is executed.
log.info("Starting Calculation Job.");
List<GroupModel> groups = Collections.emptyList();
DAOFactory hibDaoFactory = null;
try {
hibDaoFactory = DAOFactory.hibernate();
hibDaoFactory.beginTransaction();
OrganizationDao groupDao = hibDaoFactory.getGroupDao();
groups = groupDao.findAll();
hibDaoFactory.commitTransaction();
} catch (Exception ex) {
hibDaoFactory.rollbackTransaction();
log.error("Error in transaction", ex);
}
try {
hibDaoFactory = DAOFactory.hibernate();
StatsDao statsDao = hibDaoFactory.getStatsDao();
StatsScaledValuesDao statsScaledDao = hibDaoFactory.getStatsScaledValuesDao();
for (GroupModel grp : groups) {
try {
hibDaoFactory.beginTransaction();
log.info("Performing computation for Group " + grp.getName() + " ["
+ grp.getId() + "]");
List<Stats> statsDetail = statsDao.loadStatsGroup(grp.getId());
// Coputing Steps here
for (Entry origEntry : statsEntries) {
entry.setCalculatedItem1(origEntry.getCalculatedItem1());
entry.setCalculatedItem2(origEntry.getCalculatedItem2());
entry.setCalculatedItem3(origEntry.getCalculatedItem3());
StatsDetailsScaledValues scValues = entry.getScaledValues();
if (scValues == null) {
scValues = new StatsDetailsScaledValues();
scValues.setId(origEntry.getScrEntryId());
scValues.setValues(origEntry.getScaledValues());
} else {
scValues.setValues(origEntry.getScaledValues());
}
statsScaledDao.makePersistent(scValues);
}
hibDaoFactory.commitTransaction();
} catch (Exception ex) {
hibDaoFactory.rollbackTransaction();
log.error("Error in transaction", ex);
} finally {
}
}
} catch (Exception ex) {
log.error("Error", ex);
} finally {
}
log.info("Job Complete.");
Following is the exception stacktrace I am getting upon execution of this Job
org.hibernate.SessionException: Session is closed!
at org.hibernate.internal.AbstractSessionImpl.errorIfClosed(AbstractSessionImpl.java:127)
at org.hibernate.internal.SessionImpl.createCriteria(SessionImpl.java:1555)
at sun.reflect.GeneratedMethodAccessor469.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at org.hibernate.context.internal.ThreadLocalSessionContext$TransactionProtectionWrapper.invoke(ThreadLocalSessionContext.java:352)
at $Proxy308.createCriteria(Unknown Source)
at com.blueoptima.cs.dao.impl.hibernate.GenericHibernateDao.findByCriteria(GenericHibernateDao.java:132)
at com.blueoptima.cs.dao.impl.hibernate.ScrStatsManagementHibernateDao.loadStatsEntriesForOrg(ScrStatsManagementHibernateDao.java:22)
... 3 more
To my understanding from what I have read so far about Hibernate, sessions and transactions. It seems that when a session is created it is attached to the thread and lives through out the threads life or when commit or rollback is called. Thus, when the first transaction is committed the session is being closed and is unavailable for the rest of the threads life.
My question remains: How can we have multiple transactions in a single session?

More detail would be great and some examples but I think I should be able to help with what you have written here.
Have one static SessionFactory (this is big on memory)
Also with your transactions you want something like this.
SomeClass object = new SomeClass();
Session session = sessionFactory().openSession() // create the session object
session.beginTransaction(); //begins the transaction
session.save(object); // saves the object But REMEMBER it isn't saved till session.commit()
session.getTransaction().commit(); // actually persisting the object
session.close(); //closes the transaction
This is how I used my transaction, I am not sure if I do as many transaction as you have at a time. But the session object is light weight compared to the SessionFactory in memory.
If you want to save more objects at a time you could do it in one transaction for example.
SomeClass object1 = new SomeClass();
SomeClass object2 = new SomeClass();
SomeClass object2 = new SomeClass();
session.beginTransaction();
session.save(object1);
session.save(object2);
session.save(object3);
session.getTransaction().commit(); // when commit is called it will save all 3 objects
session.close();
Hope this help in some way or points you in the right direction.
I think you could configure you program to condense transactions as well. :)
Edit
Here is a great youtube tutorial. This guy really broke it down for me.
Hibernate Tutorials

Android / Java : GC_CONCURENT when creating many String's

I'm blocking with a problem from a few days. I've found some similar posts but still didn't understanding the problem of my code.
In fact, I'm reading a file (18,4Kbytes) which is containing SQL queries. So the only thing I want to do is read the file and execute the queries.
I've no problem reading the file, the problem occurs when after having executed all the queries (if I don't execute it, it works but it's not the deal!)
So here's my code (between try / catch for IO Exception):
InputStream in = ctx.getAssets().open("file.sql");
ByteArrayBuffer queryBuff = new ByteArrayBuffer(in.available());
String query = null;
int curent;
while (-1 != (curent = in.read())) {
queryBuff.append((char) curent);
if (((char) curent) == ';') {
query = new String(queryBuff.toByteArray());
db.execSQL(query);
queryBuff.clear();
query = null;
}
}
in.close();
queryBuff.clear();
And my GC_CONCURENT occurs when there is "new String" in the loop, after the end of the loop.
Thanks !
EDIT :
I'm a little annoyed, because my memory-leak didn't occurs in this part of code but in a part of code executed laterly (don't know what for now) but my problem wasn't a problem, app worked properly in fact...
Sorry !