Just wanted to say thanks for everyones input regarding my question.
Will try to implement some of the suggestions.
Re: Locking of record using SQL in JAVA Websphere application.
Joe Sam Shirah
to:
Java Programming on and around the IBM i
10/10/2012
18:22
Sent by:
java400-l-bounces@xxxxxxxxxxxx
Please respond to Java Programming on and around the IBM i
This is to mtodd:
If you're stuck/forced to use the legacy numbers, Dan's solution below
makes sense. That is, attempt to delete the row. If nothing is deleted,
presumably another user has that number, so get the next number and retry.
You can do this in a simplified way without transactions or commitment
control, by using a delete statement and executeUpdate():
iCount = ps.executeUpdate();
If the count is zero, the operation affected no rows. Notice that you
don't get an exception in this case.
Joe Sam
Joe Sam Shirah - www.conceptgo.com (904) 302-6870
conceptGO - Consulting/Development/Outsourcing
Java Filter Forum: www.ibm.com/developerworks/java
Just the JDBC FAQs: www.jguru.com/faq/JDBC
Going International? www.jguru.com/faq/I18N
Que Java400? www.jguru.com/faq/Java400
-----Original Message-----
From: Dan Kimmel
Sent: Wednesday, October 10, 2012 11:11 AM
To: Java Programming on and around the IBM i
Subject: RE: Locking of record using SQL in JAVA Websphere application.
What goes on in your deleteMemberNumber() method?
If it was me, I'd just use rs.deleteRow() in its place.
I also think you need a rollback() in your exception handlers, though
closing the connection without a commit will force a rollback.
Under commitment control, I don't think "FOR UPDATE" is going to preclude
another thread from reading the same record. You have to rely on deleteRow
()
to throw an exception in the thread that loses the race.
-----Original Message-----
From: java400-l-bounces@xxxxxxxxxxxx
[mailto:java400-l-bounces@xxxxxxxxxxxx]
On Behalf Of mtodd@xxxxxxxxxxxx
Sent: Tuesday, October 09, 2012 7:44 AM
To: java400-l@xxxxxxxxxxxx
Subject: Locking of record using SQL in JAVA Websphere application.
Have Web app that reads record from iSeries to get a unique number, then
deletes that record.
Need to make sure that only one web user gets that unique number.
Application seems to work 99% of the time but sometimes log reports
duplicate key error message when using unique number to write to
transaction file. This seems to suggest that more than one user retrieved
the unique number.
I use SQL to access the iSeries, setting the connection to
TRANSACTION_SERIALIZABLE to lock the record.
Appreciate any help on this issue.
Many thanks.
Below is the code :
sqlSelect="SELECT AMMBR# FROM MBPRDDTA.MBAMBRP WHERE AMGRWS= ? FOR UPDATE";
try{
con=AS400ConnectionManager.getInstance().getConnection();
con.setTransactionIsolation
(Connection.TRANSACTION_SERIALIZABLE);
psmt=con.prepareStatement(sqlSelect);
psmt.setString(1,memberData.getTradeIndividual());
ResultSet rs=psmt.executeQuery();
rs=psmt.executeQuery();
if(rs.next()){
response.setMemberNumber(rs.getLong("AMMBR#"));
if (deleteMemberNumber(response.getMemberNumber
(),con)){
response.setStatus
(ApplicationStatus.SUCCESS);
response.setMessage("Successfully retrieved & deleted member number from
MBAMBRP");
}
}
con.commit();
}catch (SQLException e){
response.setMessage("SQL exception : Error retrieving & deleting member
number from MBAMBRP");
e.printStackTrace();
} catch (PersistenceException e) {
response.setMessage("Persistence exception : Error retrieving & deleting
member number from MBAMBRP");
e.printStackTrace();
}
finally{
try {
psmt.close();
con.close();
} catch (SQLException e) {
response.setMessage("SQL final exception : Error retrieving & deleting
member number from MBAMBRP");
e.printStackTrace();
}
}
***********************************************************************************
CONFIDENTIALITY / DISCLAIMER NOTICE
This communication contains information which is confidential and may also
be privileged.
It is for the exclusive use of the recipient(s). If you are not the
intended recipient(s) please note that any distribution, copying or use of
this communication or the information in it is strictly prohibited.
Any views or opinions presented are solely those of the author and do not
necessarily represent those of Costco Wholesale UK Ltd. If you have
received this communication in error please notify us by e-mailing the
author or by telephoning (01923 213113) and then delete the communication
and any copies of it.
This communication is from Costco Wholesale UK Ltd whose registered office
is at UK Home Office, Hartspring Lane, Watford WD25 8JS, England.
***********************************************************************************
--
This is the Java Programming on and around the IBM i (JAVA400-L) mailing
list To post a message email: JAVA400-L@xxxxxxxxxxxx To subscribe,
unsubscribe, or change list options,
visit:
http://lists.midrange.com/mailman/listinfo/java400-l
or email: JAVA400-L-request@xxxxxxxxxxxx Before posting, please take a
moment to review the archives at
http://archive.midrange.com/java400-l.
--
This is the Java Programming on and around the IBM i (JAVA400-L) mailing
list
To post a message email: JAVA400-L@xxxxxxxxxxxx
To subscribe, unsubscribe, or change list options,
visit:
http://lists.midrange.com/mailman/listinfo/java400-l
or email: JAVA400-L-request@xxxxxxxxxxxx
Before posting, please take a moment to review the archives
at
http://archive.midrange.com/java400-l.
--
This is the Java Programming on and around the IBM i (JAVA400-L) mailing
list
To post a message email: JAVA400-L@xxxxxxxxxxxx
To subscribe, unsubscribe, or change list options,
visit:
http://lists.midrange.com/mailman/listinfo/java400-l
or email: JAVA400-L-request@xxxxxxxxxxxx
Before posting, please take a moment to review the archives
at
http://archive.midrange.com/java400-l.
***********************************************************************************
CONFIDENTIALITY / DISCLAIMER NOTICE
This communication contains information which is confidential and may also be privileged.
It is for the exclusive use of the recipient(s). If you are not the intended recipient(s)
please note that any distribution, copying or use of this communication or the information
in it is strictly prohibited.
Any views or opinions presented are solely those of the author and do not necessarily
represent those of Costco Wholesale UK Ltd. If you have received this communication in
error please notify us by e-mailing the author or by telephoning (01923 213113) and then
delete the communication and any copies of it.
This communication is from Costco Wholesale UK Ltd whose registered office is at UK Home Office,
Hartspring Lane, Watford WD25 8JS, England.
***********************************************************************************
midrange.com
