How to auto generate a sequence.

Question

Dear all
The entity Object "OrderEntryEO" has an attribute called"OrdNumber" that indicates the reference number of the order number. the order number is compose be a sequence on the year. For example 1/2011 , 2/2011 , 3/2011 and so on..
this sequence must be auto generated when pressing save button.
I have generated the entityImpl java class "OrderEntryEOImpl.java . with accessors , DO_DML method and create method.
these are the methods
{code}
protected void create(AttributeList attributeList) {
super.create(attributeList);
{code}
{code}
protected void doDML(int operation, TransactionEvent e) {
super.doDML(operation, e);
{code}
Can any one please help me how to Implement this in java code
Regards

Answer 1

I wanted to clear up what I consider to be some misinformation on this thread.
Database sequences, regardless of what magic you try (including setting the cache size to 1) can and will, by their very design have gaps. I don't care if you are doing a web app, a client server app, an SOA app, or any other newfangled or old-fashioned, red screens, green screens, blue screens - DATABASE SEQUENCES IN ORACLE CAN AND WILL HAVE GAPS.
There is only one way to ensure gap-free sequence numbers upon insert:
* You must lock the table or use some other device to serialise inserts.
Any other technique you want to use will not work in a multi-user environment. I'm not going to go through the proof of it here because it's been discussed ad-infinitum (search on asktom.oracle.com if you want to see all of the crazy failed attempts to do it without serialisation). You can also read on asktom about some other techniques (such as assigning the numbers after the fact) that you could consider.
Bottom line to remember however, Oracle Database Sequences are not and cannot be gap free (at least as of today, the 4th of April, 2011 AD at 08:48 GMT +1)
John