If two client requests arrive to the same entity object (i.e. same primary key),
the EJB container can do one of the following:
- use a different bean class instance for each transaction context, or
- use a single instance but serialize the use of the instance by the transactions
If the first method is used, the underlying resource managers will properly
isolate the work of the multiple clients.
Under no circumstances, the container should use a single instance to
dispatch multiple concurrent client requests.
Vlada
----- Original Message -----
From: Ian McCallion <[EMAIL PROTECTED]>
To: <[EMAIL PROTECTED]>
Sent: Monday, November 29, 1999 2:01 PM
Subject: Re: Transaction isolation level useless at the ejb server level ?
> Charles Paclat wrote:
>
> > Ian McCallion wrote:
> >
> > >-Not so. Two transactions concurrently accessing the same logical entity bean
> >
> > >instance will get two in-memory copies of the instance.
> >
> > Is this in the EJB spec, or is it an implementation detail?
>
> Good question. Bean providers should code assuming it (indeed they could hardly
> do otherwise without thread sync facilities), so it should be quite explicit in
> the spec, but all I can find is section 3.1.1 in the 1.0 and 1.1 specs which
> says "The Bean Provider is not required to be an expert at system-level
> programming. Therefore, the Bean Provider usually does not program transactions,
> concurrency..." This IMPLIES that what I said is true but it doesn't exactly
> come right out and say it, does it!
>
> Does any vendor care to stand up and say their server DOESN'T do it? Any
> comments from Sun?
>
> Ian McCallion
>
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