Java.sql.SQLException: Closed Statement

Question

I'm having a problem with my Java code trying to access an Oracle 10g database through the JDBC driver using the Oracle XML Publisher.
We generate a number of different reports, but one report consistently fails with the error: java.sql.SQLException: Closed Statement
It only happens in the production environment, which has significantly more data than the test and development environments.
One interesting (!) observation is that the error occurs after 10 minutes to the second (almost). Which leads me to think it is a timeout related problem, but am aware that this could be a red herring.
And finally, the code is being run within a job sheduled using the Quartz Scheduler v1.6.5.
Any help would be appreciated.
Many Thanks
Lawrence
Here is the stack trace:
java.sql.SQLException: Closed Statement: getMetaData
at oracle.jdbc.driver.DatabaseError.throwSqlException(DatabaseError.java:112)
at oracle.jdbc.driver.DatabaseError.throwSqlException(DatabaseError.java:146)
at oracle.jdbc.driver.OracleResultSetImpl.getMetaData(OracleResultSetImpl.java:128)
at com.mchange.v2.c3p0.impl.NewProxyResultSet.getMetaData(NewProxyResultSet.java:47)
at oracle.apps.xdo.dataengine.XMLPGEN.processSQLDataSource(Unknown Source)
at oracle.apps.xdo.dataengine.XMLPGEN.writeData(Unknown Source)
at oracle.apps.xdo.dataengine.XMLPGEN.writeGroup(Unknown Source)
at oracle.apps.xdo.dataengine.XMLPGEN.writeGroup(Unknown Source)
at oracle.apps.xdo.dataengine.XMLPGEN.processSQLDataSource(Unknown Source)
at oracle.apps.xdo.dataengine.XMLPGEN.writeData(Unknown Source)
at oracle.apps.xdo.dataengine.XMLPGEN.writeGroupStructure(Unknown Source)
at oracle.apps.xdo.dataengine.XMLPGEN.processData(Unknown Source)
at oracle.apps.xdo.dataengine.XMLPGEN.processXML(Unknown Source)
at oracle.apps.xdo.dataengine.XMLPGEN.writeXML(Unknown Source)
at oracle.apps.xdo.dataengine.DataProcessor.processDataStructre(Unknown Source)
at oracle.apps.xdo.dataengine.DataProcessor.processData(Unknown Source)
at com.tmobile.sett.file.invoice.InvoiceFileFactory.generateXML(InvoiceFileFactory.java:157)
at com.tmobile.sett.file.invoice.InvoiceFileFactory.generateStatements(InvoiceFileFactory.java:365)
at com.tmobile.sett.file.invoice.InvoiceFileFactory.generateInvoices(InvoiceFileFactory.java:457)
at com.tmobile.sett.file.invoice.StatementGeneratorJob.execute(StatementGeneratorJob.java:34)
at org.quartz.core.JobRunShell.run(JobRunShell.java:202)
at org.quartz.simpl.SimpleThreadPool$WorkerThread.run(SimpleThreadPool.java:525)
Here is the code:
private void generateXML(String xmlTemplate, String xmlFilename, Hashtable parameters) {
DataProcessor dataProcessor = new DataProcessor();
log.debug("generateXML: xmlTemplate {}, xmlFilename {}", xmlTemplate, xmlFilename);
try {
// Set Data Template to be executed
dataProcessor.setDataTemplate(xmlTemplate);
// Obtain a new Connection from the Pool
Connection conn = HibernateUtil.getConnection();
if (conn == null)
log.debug("conn is null after getCall");
if (conn.isClosed())
log.debug("conn is closed after getCall");
// Set the Connection for the dataProcessor
dataProcessor.setConnection(conn);
if (conn.isClosed())
log.debug("conn is closed after setConnection");
dataProcessor.setParameters(parameters);
if (conn.isClosed())
log.debug("conn is closed after setParameters");
// Specify the output directory and file for the data file
dataProcessor.setOutput(xmlFilename);
if (conn.isClosed())
log.debug("conn is closed after setOutput");
// Process the data template
dataProcessor.processData();
if (conn.isClosed())
log.debug("conn is closed after processData");
// Return the connection to the pool
conn.close();
} catch (Exception e) {
System.err.println("Error generating XML with the following parameters:");
System.err.println("xmlTemplate=" + xmlTemplate);
System.err.println("xmlFilename=" + xmlFilename);
System.err.println("Here's the stack trace");
e.printStackTrace();
System.exit(1);
}

Answer 1

I have made some progress in understanding the problem...
Basically, your comment about threads made me look at the code from a threads perspective. There are only three objects used, log4j, oracleXML Publisher and hibernate. Discounting log4j, the Oracle object is created, opened and closed within the procedure, so I concluded that hibernate was the most likely cause of the problem (i know, theres an element of educated guesswork in this).
Anyway, I found the hibernate timeouts (all around 300 seconds) and increased them to 3000 seconds... and lo and behold the reports are generated successfully, although some of them take over 20 minutes each.
So, this is a performance problem with the SQL itself:
SELECT service
, reply
, ROUND(SUM(DECODE(op, 3, 0, count))* :uplift,0) x_events
, ROUND(SUM(DECODE(op, 3, count, 0))* :uplift,0) y_events
FROM aggregate
WHERE ref_time >= :period_start
AND ref_time < :period_end
AND feed = 13
AND agreement = :agreement
AND line = 1
GROUP BY service, reply
ORDER BY 1,2
The SQL in question is querying data for a specific month from a monthly partitioned table that contains about 11 million records a month. We currently have 99 partitions.
Executing the sql in Toad / Sql developer / sqlplus takes around 20 seconds...so why 20 minutes?
Looking in the session browser, I can see that the 20 minute query is looking through all 99 partitions where the 20 second query is only looking at 1 partition for the month in question.
I'm not sure if this is heading off topic for the forum thread, but the question now is...
Why is Oracle using a clearly innefficient execution plan when we are using a query with bound variables and how do we get it to use a more efficient execution plan?