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From "Rahul Akolkar (JIRA)" <>
Subject [jira] Updated: (SCXML-65) NullPointer exceptions during triggerEvent
Date Sun, 27 Jan 2008 01:28:34 GMT


Rahul Akolkar updated SCXML-65:

    Fix Version/s: 0.8

Please try one or more of the following things:

 * From the stack trace, it looks like you are triggering events asynchronously through a
custom action. Generally, custom actions work better with derived events instead (add the
event based on the HTTP response to the 'derivedEvents' collection).

 * Alternatively (as compared to above bullet which I'd try first), you could try registering
a 'x-http' targettype invoker and using <invoke targettype="x-http" ...>

 * Looking at the trace above (and v0.7 as you indicate to match line numbers), I've made
one minor "first-hit" performance improvement to the code in SVN trunk. It'd be useful to
know if that helps the cause here (if you are in a position to be able to try a jar built
out of SVN).

 * If none of the above works, try parsing a separate state machine instance (SCXML class
instance) for each SCXMLExecutor instance. This shouldn't be necessary, but if it is here,
then this may have uncovered a bug.

In the absence of a test case, it'd be great if you could give us some feedback on the above
suggestions. Thanks.

> NullPointer exceptions during triggerEvent
> ------------------------------------------
>                 Key: SCXML-65
>                 URL:
>             Project: Commons SCXML
>          Issue Type: Bug
>    Affects Versions: 0.7
>         Environment: Linux opensuse 10.2 & Sun Solaris 10 
> 1.5.x java
>            Reporter: luc willems
>             Fix For: 0.8
> i'm using SCXML state machines in a load generation tool. this tool simulates a client
connected to a server.
> the SCXML script used custom actions to send a request using a HTTP based protocol.
> the HTTP response is transformed into a event and inserted into the SCXML script using
> each SCML executor has 1 dedicated http connection.  i'm using around 2 to 10000 clients
depending on the 
> test scenario's.
> During execution of the scripts a get sporatic nullpointer exceptions. this DOESN'T happen
all the time , it is hard to reproduce but when it happens ALL clients have the same problem.
resetting the SCXML exector doesn't help
> 2008-01-24 14:33:35,593|scxml-1-88|ERROR|SCXMLUser.triggerEvents(181)|9|Current events:
> 2008-01-24 14:33:35,594|scxml-1-88|ERROR|SCXMLUser.triggerEvents(182)|9|error scxml event
trigger: null
> java.lang.NullPointerException
>         at org.apache.commons.scxml.semantics.SCXMLSemanticsImpl.seedTargetSet(
>         at org.apache.commons.scxml.semantics.SCXMLSemanticsImpl.followTransitions(
>         at org.apache.commons.scxml.SCXMLExecutor.triggerEvents(
>         at com.nsn.loadtool.scxml.SCXMLUser.triggerEvents(
>         at com.nsn.loadtool.scxml.SCXMLAsyncExecutor$
>         at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(
>         at java.util.concurrent.ThreadPoolExecutor$
>         at
> all event triggering is done in a way that only 1 thread can trigger a event.

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