The lookupJeeTransactionManager() method in org.jbpm.pvm.internal.tx.JtaTransaction class cannot obtain TransactionManager through JNDI look up in Tomcat with JOTM. The reason is there is no separate TransactionManager implementation in JOTM. The class which provides the implementation for UserTransaction is org.objectweb.jotm.Current.java internally implements javax.transaction.TransactionManager. So if we add some code in the lookupJeeTransactionManager() method as below this works:

if (transactionManager == null)
{
UserTransaction ut = (UserTransaction) lookupFromJndi(userTransactionJndiName);
if (ut instanceof TransactionManager)

{ System.out.println("lookupJeeTransaction:: found TransactionManager"); transactionManager = ((TransactionManager) ut); }

}

We need to modify this code such a way so that it works in all server with all JTA implementation. I am in the process of making some patch for this and will send that.