Hi ks,
Wow!
I had to write a little program to test this out as i was very confused
why the synchronization block would work for multiple instances of the
Draft class.
Doh! the "" is a constant hence a non-static field with that value for
two different instances will have the same reference.
If the mutex value is changed to:
String mutex = new String("");
then things will not work.
Paul.
KSChan wrote:
> Paul,
>
> indeed, the class likes this ..
>
> @UriTemplate( "/draft" )
> @ProduceMime( "text/xml" )
> @ConsumeMime( "application/x-www-form-urlencoded" )
> class Draft {
> String mutex = "";
>
> @UriTemplate( "/aTemplate" )
> @HttpMethod( "GET" )
> public Response webServiceOperation( ... ) {
> synchronized ( mutex ) {
> // obtain JDBC connection here
> }
> // carry DB operation here
> }
> }
>
> what i do is to provide ontology processing through Jena API. I don't
> know what's happening in Jena but when there is concurrent request, the
> API's operation break ... i worked around with the above synchronization.
>
> ks.
>
> On Jan 22, 2008 6:33 PM, Paul Sandoz <Paul.Sandoz_at_sun.com
> <mailto:Paul.Sandoz_at_sun.com>> wrote:
>
> Hi ks,
>
> What are the annoations on the Draft class?
>
> Is the Draft class a singleton instantiated once per-application rather
> than per-request?
>
> If Draft is instantiated per-request then i am surprised your solution
> below will work as the mutex reference will be unique for each request.
>
> If Draft is instantiated once per-application then this should work,
> although it may not be necessary to use mutex as you can do the
> following instead:
>
> class Draft {
> public Response webServiceOperation( ... ) {
> synchronized ( this ) {
> // obtain JDBC connection here
> }
> // carry DB operation here
> }
> }
>
> if synchronizing on 'this' does not interfere with other operations you
> have defined.
>
> I am not sure how you are using the JDBC connection stuff but you might
> want to take a look at the Bookmark example, which uses JPA. There is
> limited support for DB stuff for injecting an EntityManagerFactory
> corresponding to a persistence unit name (see the web.xml file). From
> that thread safe class an entity manager can be created to perform DB
> operations using JPA.
>
> Paul.
>
> KSChan wrote:
> > Marc,
> >
> > I have solved the problem by using synchronization as normal
> threading
> > model.
> >
> > In my case, I have concurrent AJAX calls to the web service in
> which the
> > web service obtains a JDBC connection from the glassfish connection
> > pool. I don't know whether the connection obtained is the same
> among the
> > threads but I got error when the DB operation is carried out
> sometimes.
> >
> > My solution is like this ..
> >
> > class Draft {
> > String mutex = "";
> > public Response webServiceOperation( ... ) {
> > synchronized ( mutex ) {
> > // obtain JDBC connection here
> > }
> > // carry DB operation here
> > }
> > }
> >
> > ks.
> >
> > On Jan 21, 2008 4:57 PM, Paul Sandoz <Paul.Sandoz_at_sun.com
> <mailto:Paul.Sandoz_at_sun.com>
> > <mailto:Paul.Sandoz_at_sun.com <mailto:Paul.Sandoz_at_sun.com>>> wrote:
> >
> > CC'ing as ks is not a member of the users list.
> >
> > Paul.
> >
> > Marc Hadley wrote:
> > > On Jan 19, 2008, at 1:31 AM, KSChan wrote:
> > >>
> > >> I am facing a problem that more than one concurrent web
> service
> > >> threads are accessing the same resource and making something
> > wrong ...
> > >>
> > >> How can I deal with this?
> > >>
> > > The default is that Jersey will create a new resource class
> > instance for
> > > each request (thread) so unless you have some static
> fields that
> > aren't
> > > protected by a mutex then you should be OK. Can you
> describe in a
> > little
> > > more detail what your resource class looks like and what
> problem
> > you are
> > > seeing ?
> > >
> > > Thanks,
> > > Marc.
> > >
> > > ---
> > > Marc Hadley <marc.hadley at sun.com <http://sun.com>
> <http://sun.com>>
> > > CTO Office, Sun Microsystems.
> > >
> > >
> > >
> > >
> >
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> >
> > --
> > | ? + ? = To question
> > ----------------\
> > Paul Sandoz
> > x38109
> > +33-4-76188109
> >
> >
> >
> >
> > --
> > I, have a dream. I want to make my dream come true.
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>
> --
> | ? + ? = To question
> ----------------\
> Paul Sandoz
> x38109
> +33-4-76188109
>
>
>
>
> --
> I, have a dream. I want to make my dream come true.
>
> http://mr.kschan.googlepages.com <http://mr.kschan.googlepages.com>
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Paul Sandoz
x38109
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