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From Dain Sundstrom <d...@iq80.com>
Subject Re: Transactions?
Date Sat, 18 Jun 2005 01:22:59 GMT
On Jun 17, 2005, at 6:11 PM, Neal Sanche wrote:

> Dain Sundstrom wrote:
>
>> On Jun 17, 2005, at 12:04 AM, Neal Sanche wrote:
>>
>>>        UserTransaction tx = null;
>>>        InitialContext ctx = null;
>>>        try {
>>>            ctx = new InitialContext();
>>>            tx = (UserTransaction)ctx.lookup("UserTransaction");
>>>            tx.begin();
>>>            chain.doFilter(request, response);
>>>        } catch (Throwable e) {
>>>            throw new ServletException(e);
>>>        } finally {
>>>            try {
>>>                if (tx != null)
>>>                    tx.commit();
>>>                if (ctx != null)
>>>                    ctx.close();
>>>            } catch (Throwable ex) {
>>>                throw new ServletException(ex);
>>>            }
>>>        }
>>
>> Is this a servlet filter?  I don't believe it is legal to  
>> propagate a  tx out of a servlet filter (either down the chain or  
>> up the chain).
>>
>> -dain
>>
>
> Really? I guess it's not very kosher, but it certainly helps  
> simplify the code for the pages since while pages render, there's  
> always a transaction available. There are some obvious side-effects.

Well, I don't think this works on all platforms.  I remember  
Websphere being very very very strict about transactions in the web  
tier.  One reason to not wrap an entire web request in a transaction  
is you could end up holding the transaction open for a long time as  
data is force flushed to a modem user.  It is best to read/update all  
the data in one isolated tight transaction and then render the page.   
To maximize the transaction throughput you want to hold the  
transaction open as short as possible.

Having said that.  People do this all the time, and it should work in  
Geronimo.  It is way to common a pattern to not support.

> This 'not legal' statement is from a document somewhere Dain?

It is somewhere in the servlet spec.  Just search for transaction.   
They hardly ever mention transactions so it should be easy to find.   
If it isn't in the servlet spec, check the J2EE spec.

-dain


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