Re: Client issues an RPC before another RPC has finished
Ok, I found my Servlet problem. For some reason I assumed that my request
processing object is re-created for each request and I can safely use the
object variables to store a current persist/db connection. Just realized
that the object is created only once and the execute() method was overriding
the persist/db connection variable whenever a new request came.
Now I can improve the client side.
Thanks a million for flagging this one for me.
On 11/24/12 4:15 PM, "Alexey Panteleev" wrote:
> Hi Jens,
>
> What I get for the SQL exceptions are either this:
>
> com.mysql.jdbc.exceptions.jdbc4.MySQLNonTransientConnectionException: No
> operations allowed after connection closed.
>
> or
>
> com.mysql.jdbc.exceptions.jdbc4.MySQLNonTransientConnectionException: No
> operations allowed after statement closed.
>
> or
>
> java.sql.SQLException: Operation not allowed after ResultSet closed
>
> or
>
> java.lang.NullPointerException: null
>
> at com.mysql.jdbc.ResultSetImpl.findColumn(ResultSetImpl.java:1133)
> ~[mysql-connector-java-5.1.21.jar:na]
>
> All seem to relate to the db connection closed. Just trying to wrap my mind
> around how exactly the connection is closed/lost if my persist thread is still
> working, trying to extract the data.
>
>
>
> Thank you,
>
> Alexey
>
> On Saturday, November 24, 2012 10:44:11 AM UTC-8, Jens wrote:
>> If you see SQLExceptions just because the user navigates too quickly you
>> should analyse and fix your server code / database setup / querys!
>>
>> When you have solved this your only "problem" now is that both RPC callbacks
>> will be executed once their corresponding RPC request returns and this may
>> cause odd behavior in your UI if not handled. You have to detect when a user
>> leaves a page and store that fact in a field (e.g. boolean isActive). Your
>> callback should then check this field before executing its onSuccess() code.
>>
>> Using GWT Activities you would set the flag to true in Activity.start() and
>> to false in Activity.stop() and Activity.cancel().
>>
>> Following the documentation for GWT-RPC you could also let your methods
>> return "Request" instead of "void", e.g.
>> interface MyServiceAsync {
>> public Request myMethod(String s, AsyncCallback callback);
>> }
>> this allows you to cancel the request on the client side (server will still
>> do its work once the request reaches the server).
>>
>> -- J.
>>
>>
>>
>> Am Freitag, 23. November 2012 19:04:13 UTC+1 schrieb Alexey Panteleev:
>>> Hello,
>>>
>>> I've been struggling with this issue for a long time, maybe someone could
>>> help me address this finally?
>>> From time to time it happens that a user navigates to one page wich issues
>>> an RPC to our server but then quickly navigates to another page which issues
>>> yet another RPC to the server while the 1st call is still being processed by
>>> the server. In this case I always see some kind of SQLException on the
>>> server side (I guess for the 1st call) and then the client also receives an
>>> unspecified Exception.
>>>
>>> What is the best practice for dealing with these situations? Should I be
>>> canceling the 1st call before allowing the 2nd one?
>>> We use gwt-dispatch, I did not find a cancel method in that framework yet.
>>> Or should I not allow any new calls until the active one has not finished?
>>>
>>> Do you ever run into this w/ GWT?
>>>
>>> Thanks much,
>>> Alexey
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Re: Client issues an RPC before another RPC has finished
I¹ve been debugging this one some more. It¹s the SQLException that is really puzzling me. I also see that it is not the location change per se that is causing it but navigating to the same #location twice: * navigating to another location and then back to the same one while the 1st RPC is still executing * or reloading the browser page while the 1st RPC is still executing Thank you for the suggestions. Need to debug more to see what exactly is happening on the server side in this situation. On 11/25/12 8:13 AM, "RickL" wrote: > Alexey, > > FWIW, I would do as Jens suggests. It is not difficult to implement and it is > reliable. > > Rick > > On Friday, November 23, 2012 12:04:13 PM UTC-6, Alexey Panteleev wrote: >> Hello, >> >> I've been struggling with this issue for a long time, maybe someone could >> help me address this finally? >> From time to time it happens that a user navigates to one page wich issues an >> RPC to our server but then quickly navigates to another page which issues yet >> another RPC to the server while the 1st call is still being processed by the >> server. In this case I always see some kind of SQLException on the server >> side (I guess for the 1st call) and then the client also receives an >> unspecified Exception. >> >> What is the best practice for dealing with these situations? Should I be >> canceling the 1st call before allowing the 2nd one? >> We use gwt-dispatch, I did not find a cancel method in that framework yet. >> Or should I not allow any new calls until the active one has not finished? >> >> Do you ever run into this w/ GWT? >> >> Thanks much, >> Alexey -- You received this message because you are subscribed to the Google Groups "Google Web Toolkit" group. To post to this group, send email to google-web-toolkit@googlegroups.com. To unsubscribe from this group, send email to google-web-toolkit+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/google-web-toolkit?hl=en.
Re: Client issues an RPC before another RPC has finished
Alexey, FWIW, I would do as Jens suggests. It is not difficult to implement and it is reliable. Rick On Friday, November 23, 2012 12:04:13 PM UTC-6, Alexey Panteleev wrote: > > Hello, > > I've been struggling with this issue for a long time, maybe someone could > help me address this finally? > From time to time it happens that a user navigates to one page wich issues > an RPC to our server but then quickly navigates to another page which > issues yet another RPC to the server while the 1st call is still being > processed by the server. In this case I always see some kind of > SQLException on the server side (I guess for the 1st call) and then the > client also receives an unspecified Exception. > > What is the best practice for dealing with these situations? Should I be > canceling the 1st call before allowing the 2nd one? > We use gwt-dispatch, I did not find a cancel method in that framework > yet. Or should I not allow any new calls until the active one has not > finished? > > Do you ever run into this w/ GWT? > > Thanks much, > Alexey > -- You received this message because you are subscribed to the Google Groups "Google Web Toolkit" group. To view this discussion on the web visit https://groups.google.com/d/msg/google-web-toolkit/-/AUdJNaYf1zgJ. To post to this group, send email to google-web-toolkit@googlegroups.com. To unsubscribe from this group, send email to google-web-toolkit+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/google-web-toolkit?hl=en.
Re: Client issues an RPC before another RPC has finished
On the other hand I am thinking, is the activity really destroyed, if there
is already an active RPC listener?
That is an external reference to the Activity object so the GC would not
touch it, right?
On 11/24/12 4:22 PM, "Alexey Panteleev" wrote:
> Ok, I think it's a good idea for me to switch to the Activity/Places framework
> on this project also.
> So the things like that are handled by the framework automatically.
>
> Supercobra is actually saying I wont have to worry about setting that isActive
> flag as the Activity will get destroyed all together.
>
> On Saturday, November 24, 2012 10:44:11 AM UTC-8, Jens wrote:
>> If you see SQLExceptions just because the user navigates too quickly you
>> should analyse and fix your server code / database setup / querys!
>>
>> When you have solved this your only "problem" now is that both RPC callbacks
>> will be executed once their corresponding RPC request returns and this may
>> cause odd behavior in your UI if not handled. You have to detect when a user
>> leaves a page and store that fact in a field (e.g. boolean isActive). Your
>> callback should then check this field before executing its onSuccess() code.
>>
>> Using GWT Activities you would set the flag to true in Activity.start() and
>> to false in Activity.stop() and Activity.cancel().
>>
>> Following the documentation for GWT-RPC you could also let your methods
>> return "Request" instead of "void", e.g.
>> interface MyServiceAsync {
>> public Request myMethod(String s, AsyncCallback callback);
>> }
>> this allows you to cancel the request on the client side (server will still
>> do its work once the request reaches the server).
>>
>> -- J.
>>
>>
>>
>> Am Freitag, 23. November 2012 19:04:13 UTC+1 schrieb Alexey Panteleev:
>>> Hello,
>>>
>>> I've been struggling with this issue for a long time, maybe someone could
>>> help me address this finally?
>>> From time to time it happens that a user navigates to one page wich issues
>>> an RPC to our server but then quickly navigates to another page which issues
>>> yet another RPC to the server while the 1st call is still being processed by
>>> the server. In this case I always see some kind of SQLException on the
>>> server side (I guess for the 1st call) and then the client also receives an
>>> unspecified Exception.
>>>
>>> What is the best practice for dealing with these situations? Should I be
>>> canceling the 1st call before allowing the 2nd one?
>>> We use gwt-dispatch, I did not find a cancel method in that framework yet.
>>> Or should I not allow any new calls until the active one has not finished?
>>>
>>> Do you ever run into this w/ GWT?
>>>
>>> Thanks much,
>>> Alexey
--
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Re: Client issues an RPC before another RPC has finished
Jens, what if instead of using the isActive flag I check "view
.asWidget().isAttached()"?
That will return true only if the presenter's view is active, right? I
actually use this in one place already successfully.
On Saturday, November 24, 2012 10:44:11 AM UTC-8, Jens wrote:
>
> If you see SQLExceptions just because the user navigates too quickly you
> should analyse and fix your server code / database setup / querys!
>
> When you have solved this your only "problem" now is that both RPC
> callbacks will be executed once their corresponding RPC request returns and
> this may cause odd behavior in your UI if not handled. You have to detect
> when a user leaves a page and store that fact in a field (e.g. boolean
> isActive). Your callback should then check this field before executing its
> onSuccess() code.
>
> Using GWT Activities you would set the flag to true in Activity.start()
> and to false in Activity.stop() and Activity.cancel().
>
> Following the documentation for GWT-RPC you could also let your methods
> return "Request" instead of "void", e.g.
>
> interface MyServiceAsync {
> public Request myMethod(String s, AsyncCallback callback);
> }
>
> this allows you to cancel the request on the client side (server will
> still do its work once the request reaches the server).
>
> -- J.
>
>
>
> Am Freitag, 23. November 2012 19:04:13 UTC+1 schrieb Alexey Panteleev:
>>
>> Hello,
>>
>> I've been struggling with this issue for a long time,
>> maybe someone could help me address this finally?
>> From time to time it happens that a user navigates to one page wich
>> issues an RPC to our server but then quickly navigates to another page
>> which issues yet another RPC to the server while the 1st call is still
>> being processed by the server. In this case I always see some kind of
>> SQLException on the server side (I guess for the 1st call) and then the
>> client also receives an unspecified Exception.
>>
>> What is the best practice for dealing with these situations? Should I be
>> canceling the 1st call before allowing the 2nd one?
>> We use gwt-dispatch, I did not find a cancel method in that framework
>> yet. Or should I not allow any new calls until the active one has not
>> finished?
>>
>> Do you ever run into this w/ GWT?
>>
>> Thanks much,
>> Alexey
>>
>
--
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Re: Client issues an RPC before another RPC has finished
Ok, I think it's a good idea for me to switch to the Activity/Places
framework on this project also.
So the things like that are handled by the framework automatically.
Supercobra is actually saying I wont have to worry about setting that
isActive flag as the Activity will get destroyed all together.
On Saturday, November 24, 2012 10:44:11 AM UTC-8, Jens wrote:
>
> If you see SQLExceptions just because the user navigates too quickly you
> should analyse and fix your server code / database setup / querys!
>
> When you have solved this your only "problem" now is that both RPC
> callbacks will be executed once their corresponding RPC request returns and
> this may cause odd behavior in your UI if not handled. You have to detect
> when a user leaves a page and store that fact in a field (e.g. boolean
> isActive). Your callback should then check this field before executing its
> onSuccess() code.
>
> Using GWT Activities you would set the flag to true in Activity.start()
> and to false in Activity.stop() and Activity.cancel().
>
> Following the documentation for GWT-RPC you could also let your methods
> return "Request" instead of "void", e.g.
>
> interface MyServiceAsync {
> public Request myMethod(String s, AsyncCallback callback);
> }
>
> this allows you to cancel the request on the client side (server will
> still do its work once the request reaches the server).
>
> -- J.
>
>
>
> Am Freitag, 23. November 2012 19:04:13 UTC+1 schrieb Alexey Panteleev:
>>
>> Hello,
>>
>> I've been struggling with this issue for a long time,
>> maybe someone could help me address this finally?
>> From time to time it happens that a user navigates to one page wich
>> issues an RPC to our server but then quickly navigates to another page
>> which issues yet another RPC to the server while the 1st call is still
>> being processed by the server. In this case I always see some kind of
>> SQLException on the server side (I guess for the 1st call) and then the
>> client also receives an unspecified Exception.
>>
>> What is the best practice for dealing with these situations? Should I be
>> canceling the 1st call before allowing the 2nd one?
>> We use gwt-dispatch, I did not find a cancel method in that framework
>> yet. Or should I not allow any new calls until the active one has not
>> finished?
>>
>> Do you ever run into this w/ GWT?
>>
>> Thanks much,
>> Alexey
>>
>
--
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Re: Client issues an RPC before another RPC has finished
Hi Jens,
What I get for the SQL exceptions are either this:
com.mysql.jdbc.exceptions.jdbc4.MySQLNonTransientConnectionException: No
operations allowed after connection closed.
or
com.mysql.jdbc.exceptions.jdbc4.MySQLNonTransientConnectionException: No
operations allowed after statement closed.
or
java.sql.SQLException: Operation not allowed after ResultSet closed
or
java.lang.NullPointerException: null
at com.mysql.jdbc.ResultSetImpl.findColumn(ResultSetImpl.java:1133)
~[mysql-connector-java-5.1.21.jar:na]
All seem to relate to the db connection closed. Just trying to wrap my mind
around how exactly the connection is closed/lost if my persist thread is
still working, trying to extract the data.
Thank you,
Alexey
On Saturday, November 24, 2012 10:44:11 AM UTC-8, Jens wrote:
>
> If you see SQLExceptions just because the user navigates too quickly you
> should analyse and fix your server code / database setup / querys!
>
> When you have solved this your only "problem" now is that both RPC
> callbacks will be executed once their corresponding RPC request returns and
> this may cause odd behavior in your UI if not handled. You have to detect
> when a user leaves a page and store that fact in a field (e.g. boolean
> isActive). Your callback should then check this field before executing its
> onSuccess() code.
>
> Using GWT Activities you would set the flag to true in Activity.start()
> and to false in Activity.stop() and Activity.cancel().
>
> Following the documentation for GWT-RPC you could also let your methods
> return "Request" instead of "void", e.g.
>
> interface MyServiceAsync {
> public Request myMethod(String s, AsyncCallback callback);
> }
>
> this allows you to cancel the request on the client side (server will
> still do its work once the request reaches the server).
>
> -- J.
>
>
>
> Am Freitag, 23. November 2012 19:04:13 UTC+1 schrieb Alexey Panteleev:
>>
>> Hello,
>>
>> I've been struggling with this issue for a long time,
>> maybe someone could help me address this finally?
>> From time to time it happens that a user navigates to one page wich
>> issues an RPC to our server but then quickly navigates to another page
>> which issues yet another RPC to the server while the 1st call is still
>> being processed by the server. In this case I always see some kind of
>> SQLException on the server side (I guess for the 1st call) and then the
>> client also receives an unspecified Exception.
>>
>> What is the best practice for dealing with these situations? Should I be
>> canceling the 1st call before allowing the 2nd one?
>> We use gwt-dispatch, I did not find a cancel method in that framework
>> yet. Or should I not allow any new calls until the active one has not
>> finished?
>>
>> Do you ever run into this w/ GWT?
>>
>> Thanks much,
>> Alexey
>>
>
--
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Re: Client issues an RPC before another RPC has finished
Hmm, I do use MVP and I switched to Activity&Places on another project, still using a home grown Presenter+Viewer framework on this project. My AppController creates a presenter each time for a new location: new ViewPresenter(clientFactory).go(container); The presenter may issue: clientFactory.getRpcService().execute(...) But when a user navigates to another location the presenter is probably not destroyed The new location would do: new View2Presenter(clientFactory).go(container) And the 1st presenter would get destroyed only when the 1st location is revisited. That is when the view.presenter variable is reset. Hmm, I need to think about this more. Or maybe I should simply enable the Activity/Places framework for this project also. Thank you On Saturday, November 24, 2012 8:05:14 AM UTC-8, Supercobra Thatbytes wrote: > > If you use an MVP pattern this should solve your problem. In this pattern > RPCs are issued from the Presenter (Activity in GWT). Each time a user > changes Place (URL) the current Activity is destroyed and a new one is > created by the new Place for the new view. RPC callbacks that point to the > old Activity are discarded silently. > > More about places and activities in GWT: > > https://developers.google.com/web-toolkit/doc/latest/DevGuideMvpActivitiesAndPlaces > > On Friday, November 23, 2012 12:04:13 PM UTC-6, Alexey Panteleev wrote: >> >> Hello, >> >> I've been struggling with this issue for a long time, >> maybe someone could help me address this finally? >> From time to time it happens that a user navigates to one page wich >> issues an RPC to our server but then quickly navigates to another page >> which issues yet another RPC to the server while the 1st call is still >> being processed by the server. In this case I always see some kind of >> SQLException on the server side (I guess for the 1st call) and then the >> client also receives an unspecified Exception. >> >> What is the best practice for dealing with these situations? Should I be >> canceling the 1st call before allowing the 2nd one? >> We use gwt-dispatch, I did not find a cancel method in that framework >> yet. Or should I not allow any new calls until the active one has not >> finished? >> >> Do you ever run into this w/ GWT? >> >> Thanks much, >> Alexey >> > -- You received this message because you are subscribed to the Google Groups "Google Web Toolkit" group. To view this discussion on the web visit https://groups.google.com/d/msg/google-web-toolkit/-/8GOIb5Bv-BYJ. To post to this group, send email to google-web-toolkit@googlegroups.com. To unsubscribe from this group, send email to google-web-toolkit+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/google-web-toolkit?hl=en.
Re: Client issues an RPC before another RPC has finished
If you see SQLExceptions just because the user navigates too quickly you
should analyse and fix your server code / database setup / querys!
When you have solved this your only "problem" now is that both RPC
callbacks will be executed once their corresponding RPC request returns and
this may cause odd behavior in your UI if not handled. You have to detect
when a user leaves a page and store that fact in a field (e.g. boolean
isActive). Your callback should then check this field before executing its
onSuccess() code.
Using GWT Activities you would set the flag to true in Activity.start() and
to false in Activity.stop() and Activity.cancel().
Following the documentation for GWT-RPC you could also let your methods
return "Request" instead of "void", e.g.
interface MyServiceAsync {
public Request myMethod(String s, AsyncCallback callback);
}
this allows you to cancel the request on the client side (server will still
do its work once the request reaches the server).
-- J.
Am Freitag, 23. November 2012 19:04:13 UTC+1 schrieb Alexey Panteleev:
>
> Hello,
>
> I've been struggling with this issue for a long time, maybe someone could
> help me address this finally?
> From time to time it happens that a user navigates to one page wich issues
> an RPC to our server but then quickly navigates to another page which
> issues yet another RPC to the server while the 1st call is still being
> processed by the server. In this case I always see some kind of
> SQLException on the server side (I guess for the 1st call) and then the
> client also receives an unspecified Exception.
>
> What is the best practice for dealing with these situations? Should I be
> canceling the 1st call before allowing the 2nd one?
> We use gwt-dispatch, I did not find a cancel method in that framework
> yet. Or should I not allow any new calls until the active one has not
> finished?
>
> Do you ever run into this w/ GWT?
>
> Thanks much,
> Alexey
>
--
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Re: Client issues an RPC before another RPC has finished
If you use an MVP pattern this should solve your problem. In this pattern RPCs are issued from the Presenter (Activity in GWT). Each time a user changes Place (URL) the current Activity is destroyed and a new one is created by the new Place for the new view. RPC callbacks that point to the old Activity are discarded silently. More about places and activities in GWT: https://developers.google.com/web-toolkit/doc/latest/DevGuideMvpActivitiesAndPlaces On Friday, November 23, 2012 12:04:13 PM UTC-6, Alexey Panteleev wrote: > > Hello, > > I've been struggling with this issue for a long time, maybe someone could > help me address this finally? > From time to time it happens that a user navigates to one page wich issues > an RPC to our server but then quickly navigates to another page which > issues yet another RPC to the server while the 1st call is still being > processed by the server. In this case I always see some kind of > SQLException on the server side (I guess for the 1st call) and then the > client also receives an unspecified Exception. > > What is the best practice for dealing with these situations? Should I be > canceling the 1st call before allowing the 2nd one? > We use gwt-dispatch, I did not find a cancel method in that framework > yet. Or should I not allow any new calls until the active one has not > finished? > > Do you ever run into this w/ GWT? > > Thanks much, > Alexey > -- You received this message because you are subscribed to the Google Groups "Google Web Toolkit" group. To view this discussion on the web visit https://groups.google.com/d/msg/google-web-toolkit/-/dmgib3SJ-x8J. To post to this group, send email to google-web-toolkit@googlegroups.com. To unsubscribe from this group, send email to google-web-toolkit+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/google-web-toolkit?hl=en.
