Re: Long transactions
Why don't you use EJB SessionBeans with TransactionManagement BEAN, and
inject (@EJB) this session bean in session scoped managed bean. This way
you can preserve transaction along multiple requests. And yes, use
Eclipselink (it has lazy loading ;) ).
On 07/02/2010 08:07 PM, Mike Kienenberger wrote:
I am not familiar with orchestra, so I can't comment there. It has
not been an option for us up to this point.
However, if you leave a transaction active after a response, it's
always going to be an issue no matter what framework you use.
For us, the problem with holder objects is the deep hierarchy of
entities and relationships we have. We have probably close to a
thousand entities right now, and most multiple-request-spanning
transactions deal with very complex, deep, and width relationship
paths. They only work well in the simple cases where we don't need
them.
On Fri, Jul 2, 2010 at 3:39 AM, Werner Punzwerner.p...@gmail.com wrote:
Mike you left out the obvious one, simply use a conversation framework.
The problem is not transactions but it is that the entity manger is dropped
along the way hence silently detaching all objects and running you into
detached error hell. (You still can either setup your jpa provider so that
lazy loading can happen outside of transaction barriers or prefetch
everything via fetch join)
I personally found as soon as you go to a conversation framework things
become way easier (although not entirely easy)
Also what was the problem with holder objects. I personally am thinking of
moving that way especially since JPA allows to map it transparently via
queries like following select new FakeHolder(entity.id, entity) from
EntityClass entity).
The downside is that you need more logic for pushing the data back into the
entity objects before writing. But the fake holder pattern is exactly what
iBatis enforces (although it has the write back logic pushed into the
configuration) and it works out well in a web centric szenario.
WErner
Am 01.07.10 23:54, schrieb Mike Kienenberger:
I am, sort of.
You really can't leave the transaction open beyond the request
response as it may never complete.
Some of the ways you can deal with it are:
1) work with fake holder entities that get changed back into real
entities at the final commit. Very ugly -- tried this one at first,
but I don't use it anymore.
2) Work with detached objects. Reattach them back right before the
final commit. This is what I currently do.I basically invented a
Unit-Of-Work framework that runs over the top of JPA.The unit of
work has a separate persistence manager that loads an object, then
immediately detaches it. Our framework requires each object to call
save() to commit changes. When in the UoW, all save does is add the
object to a change-tracker (inserts, deletes, updates).Then when
the UoW is committed, the objects are persisted or merged, then
committed all in one method call.
But in all honesty, this approach also has caused us a lot of hassles.
We are most likely going to dump JPA and replace it with Apache
Cayenne, which uses a real unit of work concept.
Another option for you might be to use an implementation-specific unit
of work provided by your JPA implementation. However, I don't know
if you might have other issues. I used Cayenne before I used JPA,
and I know Cayenne does exactly what I need.
A third option you could consider if you want to risk leaving the
transaction open.
a) Catch the window onunload event, and mixed with ajax, send an ajax
request when the user improperly attempts to leave the page (closes
the window or browser, enters a url directly, back buttons, some other
non-transaction-friendly link clicked).
I got this far with that approach, but didn't pursue it. Note that
this can only detect when the user is about to leave the page. It
cannot do anything at that point -- you'd have to do something about
it in some other way.
window.onbeforeunload = confirmExit;
function confirmExit()
{
if (needToConfirm)
return You have attempted to leave this page. If
you have
made any changes to the fields without clicking the Save button, your
changes will be lost. Are you sure you want to exit this page?;
}
b) Some other kind of client-side state tracking so that you know when
the user has navigated away from the current multi-request task.
We're sticking a taskGroupIdentifier field on every form (ajax
included) so we know when the user does something to switch to a new
task than the one we're currently working with. Doesn't help if you
have some transaction left open and the user never hits the web server
again, but a timeout could deal with that.
In short, I think it's a difficult problem, and I think JPA is
incapable of dealing with it correctly. The other shortfall we have
is that JPA cannot rollback a
Re: Long transactions
However, if you leave a
transaction active after a response,
it's
always going to be an issue no
matter what framework
you use.
True for database connections, but not necessarily for JPA connections. At
least not if you use optimistic locking, which is the default. Ofc if you use
row locking, then the database connection needs to remain open. Reminds me of
our old CICS applications where the whole compnany got a broadcast all 5
minutes: who the hell is locking my customer sdlfsdf, damn I cannot edit
it
LieGrue,
strub
- Original Message
From: Mike Kienenberger mkien...@gmail.com
To: MyFaces Discussion users@myfaces.apache.org
Sent: Fri, July 2, 2010 8:07:34 PM
Subject: Re: Long transactions
I am not familiar with orchestra, so I can't comment there. It has
not
been an option for us up to this point.
However, if you leave a
transaction active after a response, it's
always going to be an issue no
matter what framework you use.
For us, the problem with holder objects is
the deep hierarchy of
entities and relationships we have. We have
probably close to a
thousand entities right now, and most
multiple-request-spanning
transactions deal with very complex, deep, and
width relationship
paths. They only work well in the simple cases
where we don't need
them.
On Fri, Jul 2, 2010 at 3:39 AM, Werner Punz
href=mailto:werner.p...@gmail.com;werner.p...@gmail.com wrote:
Mike you left out the obvious one, simply use a conversation framework.
The problem is not transactions but it is that the entity manger is
dropped
along the way hence silently detaching all objects and running
you into
detached error hell. (You still can either setup your jpa
provider so that
lazy loading can happen outside of transaction barriers
or prefetch
everything via fetch join)
I personally
found as soon as you go to a conversation framework things
become way
easier (although not entirely easy)
Also what was the problem
with holder objects. I personally am thinking of
moving that way
especially since JPA allows to map it transparently via
queries like
following select new FakeHolder(
href=http://entity.id;entity.id, entity) from
EntityClass
entity).
The downside is that you need more logic for pushing
the data back into the
entity objects before writing. But the fake
holder pattern is exactly what
iBatis enforces (although it has the
write back logic pushed into the
configuration) and it works out well in
a web centric szenario.
WErner
Am 01.07.10 23:54, schrieb Mike Kienenberger:
I am, sort
of.
You really can't leave the transaction open beyond
the request
response as it may never
complete.
Some of the ways you can deal with it
are:
1) work with fake holder entities that get changed
back into real
entities at the final commit. Very ugly -- tried
this one at first,
but I don't use it
anymore.
2) Work with detached objects. Reattach them
back right before the
final commit. This is what I currently do.
I basically invented a
Unit-Of-Work framework that runs over the
top of JPA.The unit of
work has a separate persistence manager
that loads an object, then
immediately detaches it. Our framework
requires each object to call
save() to commit changes. When in the
UoW, all save does is add the
object to a change-tracker (inserts,
deletes, updates).Then when
the UoW is committed, the objects
are persisted or merged, then
committed all in one method
call.
But in all honesty, this approach also has caused
us a lot of hassles.
We are most likely going to dump JPA and
replace it with Apache
Cayenne, which uses a real unit of work
concept.
Another option for you might be to use an
implementation-specific unit
of work provided by your JPA
implementation. However, I don't know
if you might have other
issues. I used Cayenne before I used JPA,
and I know Cayenne does
exactly what I need.
A third option you could consider
if you want to risk leaving the
transaction
open.
a) Catch the window onunload event, and mixed with
ajax, send an ajax
request when the user improperly attempts to
leave the page (closes
the window or browser, enters a url directly,
back buttons, some other
non-transaction-friendly link
clicked).
I got this far with that approach, but didn't
pursue it. Note that
this can only detect when the user is about to
leave the page. It
cannot do anything at that point -- you'd have
to do something about
it in some other way.
window.onbeforeunload = confirmExit;
function confirmExit()
{
if (needToConfirm)
return You have
attempted to leave this page. If
you have
made any
changes to the fields without clicking the Save button, your
changes
will be lost. Are you sure you want to exit
Re: Long transactions
Mike you left out the obvious one, simply use a conversation framework.
The problem is not transactions but it is that the entity manger is
dropped along the way hence silently detaching all objects and running
you into detached error hell. (You still can either setup your jpa
provider so that lazy loading can happen outside of transaction barriers
or prefetch everything via fetch join)
I personally found as soon as you go to a conversation framework things
become way easier (although not entirely easy)
Also what was the problem with holder objects. I personally am thinking
of moving that way especially since JPA allows to map it transparently
via queries like following select new FakeHolder(entity.id, entity)
from EntityClass entity).
The downside is that you need more logic for pushing the data back into
the entity objects before writing. But the fake holder pattern is
exactly what iBatis enforces (although it has the write back logic
pushed into the configuration) and it works out well in a web centric
szenario.
WErner
Am 01.07.10 23:54, schrieb Mike Kienenberger:
I am, sort of.
You really can't leave the transaction open beyond the request
response as it may never complete.
Some of the ways you can deal with it are:
1) work with fake holder entities that get changed back into real
entities at the final commit. Very ugly -- tried this one at first,
but I don't use it anymore.
2) Work with detached objects. Reattach them back right before the
final commit. This is what I currently do.I basically invented a
Unit-Of-Work framework that runs over the top of JPA.The unit of
work has a separate persistence manager that loads an object, then
immediately detaches it. Our framework requires each object to call
save() to commit changes. When in the UoW, all save does is add the
object to a change-tracker (inserts, deletes, updates).Then when
the UoW is committed, the objects are persisted or merged, then
committed all in one method call.
But in all honesty, this approach also has caused us a lot of hassles.
We are most likely going to dump JPA and replace it with Apache
Cayenne, which uses a real unit of work concept.
Another option for you might be to use an implementation-specific unit
of work provided by your JPA implementation. However, I don't know
if you might have other issues. I used Cayenne before I used JPA,
and I know Cayenne does exactly what I need.
A third option you could consider if you want to risk leaving the
transaction open.
a) Catch the window onunload event, and mixed with ajax, send an ajax
request when the user improperly attempts to leave the page (closes
the window or browser, enters a url directly, back buttons, some other
non-transaction-friendly link clicked).
I got this far with that approach, but didn't pursue it. Note that
this can only detect when the user is about to leave the page. It
cannot do anything at that point -- you'd have to do something about
it in some other way.
window.onbeforeunload = confirmExit;
function confirmExit()
{
if (needToConfirm)
return You have attempted to leave this page. If you
have
made any changes to the fields without clicking the Save button, your
changes will be lost. Are you sure you want to exit this page?;
}
b) Some other kind of client-side state tracking so that you know when
the user has navigated away from the current multi-request task.
We're sticking a taskGroupIdentifier field on every form (ajax
included) so we know when the user does something to switch to a new
task than the one we're currently working with. Doesn't help if you
have some transaction left open and the user never hits the web server
again, but a timeout could deal with that.
In short, I think it's a difficult problem, and I think JPA is
incapable of dealing with it correctly. The other shortfall we have
is that JPA cannot rollback a transaction. You have no way of
knowing what state your application is in once you roll back the
transaction. Again Cayenne automatically puts everything exactly
where it was at the start of your unit of work if you do a rollback.
On Thu, Jul 1, 2010 at 9:53 AM, Bruno Arandabrunoara...@gmail.com wrote:
Hi,
Is anyone here using long JPA transactions in their applications
(transactions that span more than one request) but not using Orchestra?. How
are you doing it?
Cheers,
Bruno
Re: Long transactions
Mike you left out the obvious one, simply use a conversation
framework.
Definitely true, but not always applicable. I would e.g. not recommend using
long running transactions for public pages. This will increase the session
footprint big times and you'll get more easily vulnerable for DOS attacks this
way.
Otoh, for intranet apps or pages with a limited reach, frameworks like
Orchestra will really make your life way easier.
FYI: we are currently working on getting Orchestra style conversations ported
over to our MyFaces Extensions for CDI (EXTCDI / CODI).
LieGrue,
strub
- Original Message
From: Werner Punz werner.p...@gmail.com
To: users@myfaces.apache.org
Sent: Fri, July 2, 2010 9:39:05 AM
Subject: Re: Long transactions
Mike you left out the obvious one, simply use a conversation framework.
The
problem is not transactions but it is that the entity manger is
dropped
along the way hence silently detaching all objects and running
you into
detached error hell. (You still can either setup your jpa
provider so that
lazy loading can happen outside of transaction barriers
or prefetch
everything via fetch join)
I personally found as soon as you go to a
conversation framework things
become way easier (although not entirely
easy)
Also what was the problem with holder objects. I personally am
thinking
of moving that way especially since JPA allows to map it
transparently
via queries like following select new FakeHolder(
target=_blank href=http://entity.id;entity.id, entity)
from
EntityClass entity).
The downside is that you need more logic for pushing
the data back into
the entity objects before writing. But the fake holder
pattern is
exactly what iBatis enforces (although it has the write back
logic
pushed into the configuration) and it works out well in a web centric
szenario.
WErner
Am 01.07.10 23:54, schrieb Mike
Kienenberger:
I am, sort of.
You really can't leave the
transaction open beyond the request
response as it may never
complete.
Some of the ways you can deal with it
are:
1) work with fake holder entities that get changed back
into real
entities at the final commit. Very ugly -- tried this
one at first,
but I don't use it anymore.
2) Work with
detached objects. Reattach them back right before the
final
commit. This is what I currently do.I basically invented
a
Unit-Of-Work framework that runs over the top of JPA.The
unit of
work has a separate persistence manager that loads an object,
then
immediately detaches it. Our framework requires each object
to call
save() to commit changes. When in the UoW, all save does
is add the
object to a change-tracker (inserts, deletes, updates).
Then when
the UoW is committed, the objects are persisted or
merged, then
committed all in one method call.
But in
all honesty, this approach also has caused us a lot of hassles.
We are most likely going to dump JPA and replace it with Apache
Cayenne, which uses a real unit of work concept.
Another option
for you might be to use an implementation-specific unit
of work provided
by your JPA implementation. However, I don't know
if you might
have other issues. I used Cayenne before I used JPA,
and I know
Cayenne does exactly what I need.
A third option you could
consider if you want to risk leaving the
transaction
open.
a) Catch the window onunload event, and mixed with ajax,
send an ajax
request when the user improperly attempts to leave the page
(closes
the window or browser, enters a url directly, back buttons, some
other
non-transaction-friendly link clicked).
I got this
far with that approach, but didn't pursue it. Note that
this can
only detect when the user is about to leave the page. It
cannot do
anything at that point -- you'd have to do something about
it in some
other way.
window.onbeforeunload = confirmExit;
function confirmExit()
{
if (needToConfirm)
return You have attempted to leave this page. If you
have
made any changes to the fields without clicking the Save button,
your
changes will be lost. Are you sure you want to exit this
page?;
}
b) Some other kind of client-side state tracking so
that you know when
the user has navigated away from the current
multi-request task.
We're sticking a taskGroupIdentifier field on every
form (ajax
included) so we know when the user does something to switch
to a new
task than the one we're currently working with. Doesn't
help if you
have some transaction left open and the user never hits the
web server
again, but a timeout could deal with
that.
In short, I think it's a difficult problem, and I
think JPA is
incapable of dealing with it correctly. The other
shortfall we have
is that JPA cannot rollback a transaction. You
have no way
Re: Long transactions
Hi! I know, I might sound like a broken record already ... But also consider using a JPA-like persistence provider like Ebean [1]. If you are going to deatach your objects, you can avoid the persistence context at all. Ebean just maintains a persistence context per transaction. So, if you are having processes which reads the same row from the database multiple times you'll get the same instance from the cache, but reads outside of a transaction result in immediately detached object. For sure, without the persistence context you have to call ebean.save(instance) on your entities instead of relying on a session.commit(), but this is a very low price to pay compared to all the hassle you have with a long running persistence context. Lazy loading is still possible with Ebean anyway! And not only this, it also learns (if configured) from your application which relations you use and which properties and next time will autotune the select to just fetch those properties and relation. No need to define a 1:n relation eager or lazy, it just learns that (optional for sure!). I can say, I am quite happy with this library! I even replaced Hibernate by it. Probably you have to put some effort into the transition, but for me it made things alot easier again. Ciao, Mario [1] www.avaje.org -Ursprüngliche Nachricht- Von: Mark Struberg [mailto:strub...@yahoo.de] Gesendet: Freitag, 02. Juli 2010 10:12 An: MyFaces Discussion Betreff: Re: Long transactions Mike you left out the obvious one, simply use a conversation framework. Definitely true, but not always applicable. I would e.g. not recommend using long running transactions for public pages. This will increase the session footprint big times and you'll get more easily vulnerable for DOS attacks this way. Otoh, for intranet apps or pages with a limited reach, frameworks like Orchestra will really make your life way easier. FYI: we are currently working on getting Orchestra style conversations ported over to our MyFaces Extensions for CDI (EXTCDI / CODI). LieGrue, strub - Original Message From: Werner Punz werner.p...@gmail.com To: users@myfaces.apache.org Sent: Fri, July 2, 2010 9:39:05 AM Subject: Re: Long transactions Mike you left out the obvious one, simply use a conversation framework. The problem is not transactions but it is that the entity manger is dropped along the way hence silently detaching all objects and running you into detached error hell. (You still can either setup your jpa provider so that lazy loading can happen outside of transaction barriers or prefetch everything via fetch join) I personally found as soon as you go to a conversation framework things become way easier (although not entirely easy) Also what was the problem with holder objects. I personally am thinking of moving that way especially since JPA allows to map it transparently via queries like following select new FakeHolder( target=_blank href=http://entity.id;entity.id, entity) from EntityClass entity). The downside is that you need more logic for pushing the data back into the entity objects before writing. But the fake holder pattern is exactly what iBatis enforces (although it has the write back logic pushed into the configuration) and it works out well in a web centric szenario. WErner Am 01.07.10 23:54, schrieb Mike Kienenberger: I am, sort of. You really can't leave the transaction open beyond the request response as it may never complete. Some of the ways you can deal with it are: 1) work with fake holder entities that get changed back into real entities at the final commit. Very ugly -- tried this one at first, but I don't use it anymore. 2) Work with detached objects. Reattach them back right before the final commit. This is what I currently do.I basically invented a Unit-Of-Work framework that runs over the top of JPA.The unit of work has a separate persistence manager that loads an object, then immediately detaches it. Our framework requires each object to call save() to commit changes. When in the UoW, all save does is add the object to a change-tracker (inserts, deletes, updates). Then when the UoW is committed, the objects are persisted or merged, then committed all in one method call. But in all honesty, this approach also has caused us a lot of hassles. We are most likely going to dump JPA and replace it with Apache Cayenne, which uses a real unit of work concept. Another option for you might be to use an implementation-specific unit of work provided by your JPA implementation. However, I don't know if you might have other issues. I used Cayenne before I used JPA, and I know Cayenne does exactly what I need. A third option you could consider if you want to risk leaving the transaction open. a) Catch the window onunload event, and mixed with ajax, send an ajax request
Re: Long transactions
And, btw, Orchestra is still useful then, but there is no need to attach it to the PersistenceContext then. It just acts as a simple conversation scope provider without any magic associated with the database layer. = easier spring configuration too. Ciao, Mario -Ursprüngliche Nachricht- Von: Mario Ivankovits [mailto:ma...@ops.co.at] Gesendet: Freitag, 02. Juli 2010 10:27 An: 'MyFaces Discussion' Betreff: Re: Long transactions Hi! I know, I might sound like a broken record already ... But also consider using a JPA-like persistence provider like Ebean [1]. If you are going to deatach your objects, you can avoid the persistence context at all. Ebean just maintains a persistence context per transaction. So, if you are having processes which reads the same row from the database multiple times you'll get the same instance from the cache, but reads outside of a transaction result in immediately detached object. For sure, without the persistence context you have to call ebean.save(instance) on your entities instead of relying on a session.commit(), but this is a very low price to pay compared to all the hassle you have with a long running persistence context. Lazy loading is still possible with Ebean anyway! And not only this, it also learns (if configured) from your application which relations you use and which properties and next time will autotune the select to just fetch those properties and relation. No need to define a 1:n relation eager or lazy, it just learns that (optional for sure!). I can say, I am quite happy with this library! I even replaced Hibernate by it. Probably you have to put some effort into the transition, but for me it made things alot easier again. Ciao, Mario [1] www.avaje.org -Ursprüngliche Nachricht- Von: Mark Struberg [mailto:strub...@yahoo.de] Gesendet: Freitag, 02. Juli 2010 10:12 An: MyFaces Discussion Betreff: Re: Long transactions Mike you left out the obvious one, simply use a conversation framework. Definitely true, but not always applicable. I would e.g. not recommend using long running transactions for public pages. This will increase the session footprint big times and you'll get more easily vulnerable for DOS attacks this way. Otoh, for intranet apps or pages with a limited reach, frameworks like Orchestra will really make your life way easier. FYI: we are currently working on getting Orchestra style conversations ported over to our MyFaces Extensions for CDI (EXTCDI / CODI). LieGrue, strub - Original Message From: Werner Punz werner.p...@gmail.com To: users@myfaces.apache.org Sent: Fri, July 2, 2010 9:39:05 AM Subject: Re: Long transactions Mike you left out the obvious one, simply use a conversation framework. The problem is not transactions but it is that the entity manger is dropped along the way hence silently detaching all objects and running you into detached error hell. (You still can either setup your jpa provider so that lazy loading can happen outside of transaction barriers or prefetch everything via fetch join) I personally found as soon as you go to a conversation framework things become way easier (although not entirely easy) Also what was the problem with holder objects. I personally am thinking of moving that way especially since JPA allows to map it transparently via queries like following select new FakeHolder( target=_blank href=http://entity.id;entity.id, entity) from EntityClass entity). The downside is that you need more logic for pushing the data back into the entity objects before writing. But the fake holder pattern is exactly what iBatis enforces (although it has the write back logic pushed into the configuration) and it works out well in a web centric szenario. WErner Am 01.07.10 23:54, schrieb Mike Kienenberger: I am, sort of. You really can't leave the transaction open beyond the request response as it may never complete. Some of the ways you can deal with it are: 1) work with fake holder entities that get changed back into real entities at the final commit. Very ugly -- tried this one at first, but I don't use it anymore. 2) Work with detached objects. Reattach them back right before the final commit. This is what I currently do.I basically invented a Unit-Of-Work framework that runs over the top of JPA.The unit of work has a separate persistence manager that loads an object, then immediately detaches it. Our framework requires each object to call save() to commit changes. When in the UoW, all save does is add the object to a change-tracker (inserts, deletes, updates). Then when the UoW is committed, the objects are persisted or merged, then committed all in one method call. But in all honesty, this approach also has caused us a lot of hassles. We are most likely going to dump JPA and replace it with Apache Cayenne, which uses a real unit of work concept
Re: Long transactions
I am not familiar with orchestra, so I can't comment there. It has
not been an option for us up to this point.
However, if you leave a transaction active after a response, it's
always going to be an issue no matter what framework you use.
For us, the problem with holder objects is the deep hierarchy of
entities and relationships we have. We have probably close to a
thousand entities right now, and most multiple-request-spanning
transactions deal with very complex, deep, and width relationship
paths. They only work well in the simple cases where we don't need
them.
On Fri, Jul 2, 2010 at 3:39 AM, Werner Punz werner.p...@gmail.com wrote:
Mike you left out the obvious one, simply use a conversation framework.
The problem is not transactions but it is that the entity manger is dropped
along the way hence silently detaching all objects and running you into
detached error hell. (You still can either setup your jpa provider so that
lazy loading can happen outside of transaction barriers or prefetch
everything via fetch join)
I personally found as soon as you go to a conversation framework things
become way easier (although not entirely easy)
Also what was the problem with holder objects. I personally am thinking of
moving that way especially since JPA allows to map it transparently via
queries like following select new FakeHolder(entity.id, entity) from
EntityClass entity).
The downside is that you need more logic for pushing the data back into the
entity objects before writing. But the fake holder pattern is exactly what
iBatis enforces (although it has the write back logic pushed into the
configuration) and it works out well in a web centric szenario.
WErner
Am 01.07.10 23:54, schrieb Mike Kienenberger:
I am, sort of.
You really can't leave the transaction open beyond the request
response as it may never complete.
Some of the ways you can deal with it are:
1) work with fake holder entities that get changed back into real
entities at the final commit. Very ugly -- tried this one at first,
but I don't use it anymore.
2) Work with detached objects. Reattach them back right before the
final commit. This is what I currently do. I basically invented a
Unit-Of-Work framework that runs over the top of JPA. The unit of
work has a separate persistence manager that loads an object, then
immediately detaches it. Our framework requires each object to call
save() to commit changes. When in the UoW, all save does is add the
object to a change-tracker (inserts, deletes, updates). Then when
the UoW is committed, the objects are persisted or merged, then
committed all in one method call.
But in all honesty, this approach also has caused us a lot of hassles.
We are most likely going to dump JPA and replace it with Apache
Cayenne, which uses a real unit of work concept.
Another option for you might be to use an implementation-specific unit
of work provided by your JPA implementation. However, I don't know
if you might have other issues. I used Cayenne before I used JPA,
and I know Cayenne does exactly what I need.
A third option you could consider if you want to risk leaving the
transaction open.
a) Catch the window onunload event, and mixed with ajax, send an ajax
request when the user improperly attempts to leave the page (closes
the window or browser, enters a url directly, back buttons, some other
non-transaction-friendly link clicked).
I got this far with that approach, but didn't pursue it. Note that
this can only detect when the user is about to leave the page. It
cannot do anything at that point -- you'd have to do something about
it in some other way.
window.onbeforeunload = confirmExit;
function confirmExit()
{
if (needToConfirm)
return You have attempted to leave this page. If
you have
made any changes to the fields without clicking the Save button, your
changes will be lost. Are you sure you want to exit this page?;
}
b) Some other kind of client-side state tracking so that you know when
the user has navigated away from the current multi-request task.
We're sticking a taskGroupIdentifier field on every form (ajax
included) so we know when the user does something to switch to a new
task than the one we're currently working with. Doesn't help if you
have some transaction left open and the user never hits the web server
again, but a timeout could deal with that.
In short, I think it's a difficult problem, and I think JPA is
incapable of dealing with it correctly. The other shortfall we have
is that JPA cannot rollback a transaction. You have no way of
knowing what state your application is in once you roll back the
transaction. Again Cayenne automatically puts everything exactly
where it was at the start of your unit of work if you do a rollback.
On Thu, Jul 1, 2010 at
Long transactions
Hi, Is anyone here using long JPA transactions in their applications (transactions that span more than one request) but not using Orchestra?. How are you doing it? Cheers, Bruno
Re: Long transactions
I am, sort of.
You really can't leave the transaction open beyond the request
response as it may never complete.
Some of the ways you can deal with it are:
1) work with fake holder entities that get changed back into real
entities at the final commit. Very ugly -- tried this one at first,
but I don't use it anymore.
2) Work with detached objects. Reattach them back right before the
final commit. This is what I currently do.I basically invented a
Unit-Of-Work framework that runs over the top of JPA.The unit of
work has a separate persistence manager that loads an object, then
immediately detaches it. Our framework requires each object to call
save() to commit changes. When in the UoW, all save does is add the
object to a change-tracker (inserts, deletes, updates).Then when
the UoW is committed, the objects are persisted or merged, then
committed all in one method call.
But in all honesty, this approach also has caused us a lot of hassles.
We are most likely going to dump JPA and replace it with Apache
Cayenne, which uses a real unit of work concept.
Another option for you might be to use an implementation-specific unit
of work provided by your JPA implementation. However, I don't know
if you might have other issues. I used Cayenne before I used JPA,
and I know Cayenne does exactly what I need.
A third option you could consider if you want to risk leaving the
transaction open.
a) Catch the window onunload event, and mixed with ajax, send an ajax
request when the user improperly attempts to leave the page (closes
the window or browser, enters a url directly, back buttons, some other
non-transaction-friendly link clicked).
I got this far with that approach, but didn't pursue it. Note that
this can only detect when the user is about to leave the page. It
cannot do anything at that point -- you'd have to do something about
it in some other way.
window.onbeforeunload = confirmExit;
function confirmExit()
{
if (needToConfirm)
return You have attempted to leave this page. If you
have
made any changes to the fields without clicking the Save button, your
changes will be lost. Are you sure you want to exit this page?;
}
b) Some other kind of client-side state tracking so that you know when
the user has navigated away from the current multi-request task.
We're sticking a taskGroupIdentifier field on every form (ajax
included) so we know when the user does something to switch to a new
task than the one we're currently working with. Doesn't help if you
have some transaction left open and the user never hits the web server
again, but a timeout could deal with that.
In short, I think it's a difficult problem, and I think JPA is
incapable of dealing with it correctly. The other shortfall we have
is that JPA cannot rollback a transaction. You have no way of
knowing what state your application is in once you roll back the
transaction. Again Cayenne automatically puts everything exactly
where it was at the start of your unit of work if you do a rollback.
On Thu, Jul 1, 2010 at 9:53 AM, Bruno Aranda brunoara...@gmail.com wrote:
Hi,
Is anyone here using long JPA transactions in their applications
(transactions that span more than one request) but not using Orchestra?. How
are you doing it?
Cheers,
Bruno
