Nested transactions / suspending transactions.

mnbv0987 · **Joined:** Sun Jan 11, 2009 2:47 pm **Posts:** 21

Hibernate version: 3.3.0 CR1

Name and version of the database you are using: MS SQL Server 2005

I have a web application that consists of various servlets and JSP pages, with Hibernate at the back-end. I am using the "Open Session In View" model, implemented as a servlet filter that opens the transaction and commits/rolls back at the end.

This works great for the servlets and most of the JSP pages. However, I now have a JSP page that needs to open and commit/rollback a separate transaction on the same database without affecting the session opened by the servlet filter (the reason I need to do this relates to software design that I can not change, the details are too gory to get into here). This separate transaction only reads data, it does not write data, if that simplifies things.

I remember reading something about suspending transactions a while ago when I didn't need to do it, and now I can't remember what I read or where I read it. I seem to remember something about being able to suspend the current transaction, start and complete a new one, then resume the old? What's a good way to make this work? Currently, the servlet filter does something like this around the whole request (I've simplified a lot of the code here, left out logging, exception handling on rollback, and I also have the ability to roll back even if an exception is not thrown):

Code:

  Session s = mySessionFactory.getCurrentSession();
  try {
    s.beginTransaction();
    handleRequest(...);
    s.commitTransaction();
  } catch (Throwable t) {
    s.rollbackTransaction();
  }

And the "inner" transaction is opened / closed in a similar way. So, the question is: What's the best way to put that "inner" transaction inside the servlet filter transaction and still have everything work OK?

Thanks,
JC

Madan_Prabhu · **Posted:** Mon Jan 12, 2009 5:33 am

Use explicit transaction object for every DB operation and commit() urself in finally block and rollback() in catch block.

*) Don't use implicit transaction. i.e., if u r not specify any Transaction it's taken as implicit transaction by default in DB layer.

mnbv0987 · **Joined:** Sun Jan 11, 2009 2:47 pm **Posts:** 21

Madan_Prabhu wrote:

Use explicit transaction object for every DB operation and commit() urself in finally block and rollback() in catch block.

*) Don't use implicit transaction. i.e., if u r not specify any Transaction it's taken as implicit transaction by default in DB layer.

Thanks. The problem is, I don't really have access to the Transaction at the JSP level, because it's all abstracted away behind the DB layer. I don't really have a good way of obtaining the open Transaction and passing it to other pieces of code.

Is there a way to detect if a Transaction already exists? E.g., can I do something like this:

Code:

  if (TransactionAlreadyOpen())
    PerformOperation(ExistingTransaction);
  else {
    try {
      PerformOperation(OpenNewTransaction());
      CommitNewTransaction();
    } catch (Throwable t) {
      RollbackNewTransaction();
      throw;
    }
  }

The idea is to use the existing Transaction if it's open, otherwise open a new one. Is this possible? I have a Session and a SessionFactory to work with at that level.

Thanks!
J

mnbv0987 · **Joined:** Sun Jan 11, 2009 2:47 pm **Posts:** 21

Oops, double post, sorry.

Madan_Prabhu · **Posted:** Mon Jan 12, 2009 6:41 am

Transaction trx=session.getTransaction();
if(trx==null)
trx=session.beginTransaction();

use this template for obtaining existing transaction object, if it returns null (i.e., no previous transaction) create ur new transaction.

mnbv0987 · **Joined:** Sun Jan 11, 2009 2:47 pm **Posts:** 21

Madan_Prabhu wrote:

use this template for obtaining existing transaction object, if it returns null (i.e., no previous transaction) create ur new transaction.

Cool, thanks a lot for your help!

J