[rules-users] How to do Exception Handling???

[Kris Verlaenen]

Miguel,

I think your work item handler should not be throwing an exception, just because a java exception is low-level and linked to one specific implementation and we try to keep the processes a little higher-level.

So what could you do then to model exceptional situations when executing a work item?  I suggest you use a try-catch block to catch the java exception and translate that into something higher-level, like:

 - your work item can contain result parameters, in case of some failure you could fill in a special result parameter with some data, the process instance can then map this result data to some process variable which will allow you to use this data, for example in a XOR split node immediate after this work item node to check for exceptional situations, or in an on-exit action linked to the workItemNode (which could then for example also throw a fault so that the nested exception handler mechanism kicks in)

 - your work item handler could decide to send a signal to the process instance to signal the occurrence of some exceptional event, and you could use an event handler to listen to that event

Depending on your exact use case, I can probably think of a few more alternatives (like using abortWorkItem instead of completeWorkItem), but they might not be all ready to use out-of-the-box.

Kris


----- Original Message ----- 
  From: miguel machado 
  To: Rules Users List 
  Sent: Thursday, April 01, 2010 1:57 PM
  Subject: Re: [rules-users] How to do Exception Handling???


  Hi,


  I'm not sure this will help you out, but in what comes to the system i'm currently developing (using drools expert), i've got this method "runRuleEngine" that collects facts and fire rules on them and i am able to catch any sort of error within the drools execution by surrounding that with try {} catch (Exception e) {}. 


  The important part is that it took me a while to figure that out cuz eclipse didn't force me handle that, as if the called method didn't have "throws" (it usually shows a compilation error otherwise, right?).


  Just a thought.
  _ miguel





  On Wed, Mar 31, 2010 at 9:44 PM, nanic23 <nanic23 at hotmail.com> wrote:


    I have a ruleflow that handles exceptions when they are raised by a "Fault"
    node but I am not being able to accomplish the same if an exception is
    thrown by a workItem or an action node instead.

    I have a workItem node with a work item handler that throws a
    RuntimeException. My exception handler in the composite node is not catching
    this exception.

    So, question
    1) how can I handle runtime exceptions thrown by my workItemHandlers?
    2) how can I get a hold of the exception to log the stack trace?

    Any ideas or tips are very appreciated.

    Nick.
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