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Design pattern for routing to multiple jBPM processes?
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created by <a href="https://community.jboss.org/people/jamesbeam">Jim B</a> in <i>jBPM</i> - <a href="https://community.jboss.org/message/804680#804680">View the full discussion</a>
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<div class="jive-rendered-content"><p>I am using jBPM 5.4 with persistence.  I am still a jBPM noob, so thanks in advance for your patience getting through this explanation...</p><p style="min-height: 8pt; height: 8pt; padding: 0px;"> </p><p>I have a ksession that will be running multiple long-running processes.  These process flows are the same - only the variables in the processes are different.  </p><p style="min-height: 8pt; height: 8pt; padding: 0px;"> </p><p>The basic use case it that I have events coming into a "router" that based upon message content will be passed to an existing process instance (if the related process exists).  If a process instance does not yet exist for that event, a new one is created.  </p><p style="min-height: 8pt; height: 8pt; padding: 0px;"> </p><p>I would greatly appreciate any thoughts on design patterns to implement this (managing processes in the kession and routing events to them).</p><p style="min-height: 8pt; height: 8pt; padding: 0px;"> </p><p>Relating to design, I have considered; </p><p style="min-height: 8pt; height: 8pt; padding: 0px;"> </p><p>1) Create a single-node process with a "routing" WorkItemHandler node.  This instance will receive the event and perform all of the checking/routing/process instantiation logic.  Basically, iterate through each process in the kession for the </p><p style="min-height: 8pt; height: 8pt; padding: 0px;"> </p><p>2) Create business rules that checks for (and creates) objects in the ksession representing each process that is running.</p><p style="min-height: 8pt; height: 8pt; padding: 0px;"> </p><p>   Pseudo code for rules would be something like:</p><p style="min-height: 8pt; height: 8pt; padding: 0px;"> </p><p>   rule "Send to existing process"</p><p>        when</p><p>              $newEventBean : NewEventBean()</p><p>              $myProcessBean : MyProcessBean(subject matches $newEventBean.subject)</p><p>        then </p><p>             <signal  $myProcessBean.processId  with $newEventBean></p><p style="min-height: 8pt; height: 8pt; padding: 0px;"> </p><p>   rule "Create if process doesn't exist"</p><p>        when</p><p>              $newEventBean : NewEventBean()</p><p>              not($myProcessBean : MyProcessBean(subject matches $newEventBean.subject))</p><p>         then </p><p>              $newProcessBean: NewProcessBean();</p><p>              $newProcessBean.subject = $newEventBean.subject;</p><p>              $newProcessBean.instantiate(thisKsession);       <<---inserts new process instance into ksession</p><p>              insert($newProcessBean);</p><p style="min-height: 8pt; height: 8pt; padding: 0px;"> </p><p>     (and when a process ends, it would need to retract the related newProcessBean)</p><p style="min-height: 8pt; height: 8pt; padding: 0px;"> </p><p>I am more familiar with java development than drools rule-jbpm integration, so I am leaning towards option 1.  (Specifically, for example, I'm not sure how to create a process from a rule or how to signal one, so I'd more likely to implement methods like NewProcessBean.instantiate() in a java method in my newProcessBean anyway <span> :) </span>)</p><p style="min-height: 8pt; height: 8pt; padding: 0px;"> </p><p>Any thoughts about option 1 or 2?  Am I missing a more obvious/better solution?</p><p style="min-height: 8pt; height: 8pt; padding: 0px;"> </p><p>(Possibly something like sending a signal to a ksession where the correct process catches it and acknowledges it in some way - so that if an acknowledgement isn't received a new process is created.  Can a process be configured to ALWAYS catch a signal AFTER another process, so that my "final" process could act like an "otherwise" statement and would just instantiate a new process?)</p><p style="min-height: 8pt; height: 8pt; padding: 0px;"> </p><p>Thank you again for any thoughts,</p><p style="min-height: 8pt; height: 8pt; padding: 0px;"> </p><p>-J</p></div>
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