ooops!
My Question was
If this is not right method then how should I save my processInstance.

In my code (for which output is given)

Token token = processInstance.getRootToken();
System.out.println("token is"+token);
token.signal();
System.out.println("token.signal() is done");

Do you think taht instead of using jbpmSession and JbpmSessionFactory, I should use JbpmConfiguration and jbpmContext?

Please suggest.
Whats the plan!

ok!
One more thing!
I followed qweniden's suggestion. and changed my method to

public long uploadDocument(String processDefinitionName) {
 long processInstanceId = 0;

 JbpmContext jbpmContext = jbpmConfiguration.createJbpmContext();
 System.out.println("jbpmContext is:"+jbpmContext);
 ProcessDefinition processDefinition = jbpmContext.getGraphSession().findLatestProcessDefinition(processDefinitionName);
 try {
 ProcessInstance processInstance =
 new ProcessInstance(processDefinition);
 System.out.print("processInstance is "+processInstance);
 Token token = processInstance.getRootToken();
 System.out.println("now saving GraphSession");
 GraphSession graphSession = jbpmContext.getGraphSession();
 System.out.println("graphSession is "+graphSession);
 //saving jbpmContext
 jbpmContext.save(processInstance);
 System.out.println("saved process instance processInstance is"+processInstance);

 processInstanceId = processInstance.getId();
 System.out.println("processInstanceId is : "+processInstanceId);

 } catch (Exception ex) {
 System.out.println("In catch method ");
 }
 return processInstanceId;
 }

10:04:16,652 INFO [STDOUT] jbpmContext is:org.jbpm.JbpmContext@4845f3
10:04:16,785 INFO [STDOUT] processInstance is org.jbpm.graph.exe.ProcessInstance@19c03e7
10:04:16,785 INFO [STDOUT] now saving GraphSession
10:04:16,785 INFO [STDOUT] graphSession is org.jbpm.db.GraphSession@179e567
10:04:16,788 INFO [STDOUT] saved process instance processInstance isorg.jbpm.graph.exe.ProcessInstance@19c03e7
10:04:16,788 INFO [STDOUT] processInstanceId is : 478

huh!
Okay! I found out that
i have to save jbpmContext (jbpmContext.save()) before returning processInstanceID and then it saves the processInstance.

Still I would like to ask,
Should I use jbpmSessionFactory and jbpmSession at all?
and as JbpmConfiguration is static can I use it in my ejbcreate() and use it? ( I mean thats the way I am doing it now)

Thanks and regards,

oops! its jbpmContext.close() not jbpmContext.save()