cause eclipselink ;)
Romain Manni-Bucau Twitter: @rmannibucau Blog: http://rmannibucau.wordpress.com/ LinkedIn: http://fr.linkedin.com/in/rmannibucau Github: https://github.com/rmannibucau 2014-05-21 17:11 GMT+02:00 Jean-Louis Monteiro <[email protected]>: > I don't see why, except if you are explicitly checking for database > constraints in your code. > Because, the default JDBC connection isolation level is READ COMMITTED > AFAIR or REPEATABLE_READ for MySQL. > > Anyway, that means that you can never read uncommitted data. > > JLouis > > -- > Jean-Louis Monteiro > http://twitter.com/jlouismonteiro > http://www.tomitribe.com > > > On Wed, May 21, 2014 at 7:58 AM, Howard W. Smith, Jr. < > [email protected]> wrote: > > > removing the manual/forced entityManager.flush() broke my app in a few > > places. reverting to previous version and I may try to revisit this > later. > > :) > > > > > > > > On Wed, May 21, 2014 at 10:00 AM, Howard W. Smith, Jr. < > > [email protected]> wrote: > > > > > Thanks Jean-Louis. Based on your response, i just commented out > > > entityManager.flush() in my AbstractFacade.java for create, edit, and > > > remove methods. > > > > > > i did some testing in my app, and seems to work well. will see how my > app > > > performs under load and when users are logged in and working, > > concurrently. > > > > > > thanks again. > > > > > > > > > > > > On Wed, May 21, 2014 at 5:21 AM, Jean-Louis Monteiro < > > > [email protected]> wrote: > > > > > >> As a general rule, I would recommend to never call flush(). The JPA > > >> provider optimizing the flushing to avoid connections between the > > >> Persistence Context and the rdbms. > > >> > > >> Of course at least at the end of the transaction (commit) the JPA > > provider > > >> flushes. > > >> But for example, when you have a loop with search, read, update .... > the > > >> JPA provider is able to detect that there is a risk of dealing with > > stale > > >> object and will therefor flush as well. > > >> > > >> The only case I call flush is basically when as mentioned already, I > > need > > >> to check database constraints (Unique, etc). > > >> The only reason is that I want to explicitly catch the exception > either > > to > > >> ignore, retry, or rethrow using a business exception. > > >> > > >> Sometimes, I also use an ejb with a REQUIRES_NEW, so that the current > > >> transaction is suspended and a new one is created. Then, if an > exception > > >> occurs at commit time, I can catch in the current bean without > changing > > >> the > > >> status of the current transaction. > > >> > > >> JLouis > > >> > > >> > > >> > > >> -- > > >> Jean-Louis Monteiro > > >> http://twitter.com/jlouismonteiro > > >> http://www.tomitribe.com > > >> > > >> > > >> On Mon, May 19, 2014 at 8:47 AM, Howard W. Smith, Jr. < > > >> [email protected]> wrote: > > >> > > >> > Interesting question and answer. > > >> > > > >> > Per my 2+ year experience with Java EE 6, in my app, i used NetBeans > > to > > >> > develop my JPA session facade (@EJB JPA DAO) classes, including > > abstract > > >> > class. In the abstract class, in the create and edit methods, I did > > add > > >> > flush(), so after every create and edit JPA request, data is written > > >> > immediately. > > >> > > > >> > Honestly, I don't have any need to use @Scheduler or timer methods > to > > >> > ensure data is saved....successfully. > > >> > > > >> > In fact, I can maybe even remove flush(), but I have not done that > > >> (yet). > > >> > If I did remove flush() in my abstract class, then I would need to > > test > > >> the > > >> > app, accordingly, to see the impact. > > >> > > > >> > I really don't see any performance issues with my > > >> approach/implementation, > > >> > but the app does not have many concurrent > > >> > users/database-update-requests/etc. > > >> > > > >> > > > >> > > > >> > On Mon, May 19, 2014 at 4:02 AM, Andy Gumbrecht < > > >> [email protected] > > >> > >wrote: > > >> > > > >> > > Hi there Radhakrishna, > > >> > > > > >> > > > > >> > > On 19/05/2014 08:15, Radhakrishna Kalyan wrote: > > >> > > > > >> > >> Hi, > > >> > >> > > >> > >> I have question around entityManager.flush(). > > >> > >> Is it ok to call multiple times? Or will there be any performance > > >> issue. > > >> > >> > > >> > > Every time you hit the the database you will take a performance > hit > > >> back > > >> > - > > >> > > How much is impossible to say and is very dependant on what your > app > > >> is > > >> > > doing. Just always think along the lines of 'how can I do this > with > > >> less' > > >> > > and you'll be fine. > > >> > > > > >> > > > > >> > >> My case is, I have a timer service which executes periodically > > where > > >> I > > >> > >> create a database entity using a dao object using > > >> > entityManager.persist(), > > >> > >> after that I also call entityManager.flush(). > > >> > >> > > >> > >> The reason to do so is, if database commit fails due to certain > > >> reason > > >> > >> like > > >> > >> unique constrain exception then I want the timer service to send > a > > >> JMS > > >> > >> message. > > >> > >> > > >> > > What you are doing is not necessarily wrong, but why not just let > > the > > >> > > container do the work for you. The container managed transactions > > are > > >> > your > > >> > > friend. > > >> > > > > >> > > > > >> > >> If I don't call entityManager.flush() then I am not able to catch > > any > > >> > >> exception in my timer service thus fails to send any JMS message. > > >> > >> > > >> > > In your service look up another local bean that handles the > > >> persistence > > >> > > and if required sends a message on success, this will all run in > a > > >> > > transacted context - The success message will only be sent if the > > bean > > >> > > method actually completes. > > >> > > If the bean method call fails then you can catch the error and do > > the > > >> > > extra leg work to send the 'fail' message. > > >> > > > > >> > > > > >> > >> However at the end the database entity is never created which is > > >> > correct. > > >> > >> But if I can't able to send the JMS message upon exception then I > > >> does > > >> > not > > >> > >> meet the requirement. > > >> > >> > > >> > >> Any ideas or recommendations to do it in a better way > > >> > >> > > >> > >> > > >> > >> So I guess my suggestion is to not try and do all the work in > the > > >> timer > > >> > > service method, rather call another bean method do do the work. > > >> > > > > >> > > Andy. > > >> > > > > >> > > -- > > >> > > Andy Gumbrecht > > >> > > > > >> > > http://www.tomitribe.com > > >> > > [email protected] > > >> > > https://twitter.com/AndyGeeDe > > >> > > > > >> > > TomEE treibt Tomitribe! | http://tomee.apache.org > > >> > > > > >> > > > > >> > > > >> > > > > > > > > >
