4 Replies Latest reply on Aug 5, 2013 8:41 PM by skumar0105

    Error starting process instance - getting  HTTP 500: Unknown error


      Hi ,


      I have created a  simple bpmn job using jbpm 5.4 libraries "start --->  task -> and end event". I have attached a custom work item handler to the task ( CustomHandler.java) . I have been able to successfully commit the bpm file into guvnor and compile the package. The Jar file is copied into \jboss-as-7.1.1.Final\standalone\deployments\jbpm-gwt-console-server.war\WEB-INF\lib\ folder.


      When I open the  jbpm console (http://localhost:8080/jbpm-console/ ) i can see the process listed , but when I try to click start the process it errors out with the following msg :



      2013-07-31 16:23:37,610 [ERROR] <ul><li>URL: 'http://localhost:8080/gwt-console-server/rs/process/definition/com.sample.bpmn.sampleHTformvariables/new_instance'

      <li>Action: 'org.jboss.bpm.console.client.process.StartNewInstanceAction'

      <li>Exception: 'class com.google.gwt.http.client.RequestException'</ul>


      HTTP 500: Unknown error


      HTTP 500: Unknown error



      When I replace the Task with a User Task , the process starts without any issues.


      I would appreciate some assistance on this , have been dealing with this issue for the past few days !


      Thanks in advance



        • 1. Re: Error starting process instance - getting  HTTP 500: Unknown error

          you need to configure work item handler in console as it cannot register it on the session which is most likely the root cause of the error. Take a look at documentation for details on how to configure it.



          • 2. Re: Error starting process instance - getting  HTTP 500: Unknown error

            Hi Maciej,


            Thanks for your reply. I went through the documentation and followed the steps . First , created a sampleprocess.bpmn with - start --->  task (CustomHandler) -> and end event .


            2) Wrote a CustomHandler.java workItem handler class


            package com.sample.bpmn.project;


            import org.apache.log4j.Logger;

            import org.drools.runtime.process.WorkItemHandler;

            import org.drools.runtime.process.WorkItem;

            import org.drools.runtime.process.WorkItemManager;




            public class CustomHandler implements WorkItemHandler {

               static Logger log = Logger.getLogger(





                public void abortWorkItem(WorkItem workItem, WorkItemManager manager) {       

                    // extract parameters       

                  System.out.println("aborting *****");






                public void executeWorkItem(WorkItem workItem, WorkItemManager manager) {


                   System.out.println("The custom work handler is successfully invoked");     

                   log.info("The custom work handler is successfully invoked");

                   manager.completeWorkItem(workItem.getId(), null);








            and packaged it into a .jar and  copied it into ..\jboss-as-7.1.1.Final\standalone\deployments\jbpm-gwt-console-server.war\WEB-INF\lib\  and ..\jbpm-installer\jboss-as-7.1.1.Final\standalone\lib directories.


            3) In guvnor, created a workitem defintion CustomWorkItemHandler ( Not sure if this is required )



            import org.drools.process.core.datatype.impl.type.ObjectDataType;

            import org.drools.process.core.datatype.impl.type.StringDataType;





                "name" : "CustomHandler",

                "parameters" : [

                    "MyFirstParam" : new StringDataType(),

                    "MySecondParam" : new StringDataType(),

                    "MyThirdParam" : new ObjectDataType()


                "results" : [

                    "Result" : new ObjectDataType()


                "displayName" : "CustomHandler",

                "icon" : "",





            Successfully packaged and deployed the sampleprocess and wid into the GWT console server via guvnor.



            4) Modified the CustomWorkItemHandlers.conf file and added the following entry



              "Log": new org.jbpm.process.instance.impl.demo.SystemOutWorkItemHandler(), 

            "CustomHandler": new com.sample.bpmn.project.CustomHandler(),



            5) Restarted the server . I was able to see the SampleProcess in the webconsole , but when I tried to start it , blew up again with the same error message .


            I am really frustrated , not sure what I am missing here. . Any help would be highly appreciated .





            • 3. Re: Error starting process instance - getting  HTTP 500: Unknown error

              Step 2, it's enough to place it in jbpm-gwt-console-server.war\WEB-INF\lib

              Step 3 is not really needed for runtime.


              where is this file (CustomWorkItemHandlers.conf) located? If you look at 5.4 documentation and the link I placed previously you'll notice that there is something called session.template that can be used to configure handlers as well.

              In server.log you should see more details about the error.



              1 of 1 people found this helpful
              • 4. Re: Error starting process instance - getting  HTTP 500: Unknown error

                Thanks for your reply . The CustomWorkItemHandlers.conf file is located within the jboss-as-7.1.1.Final\standalone\deployments\jbpm-gwt-console-server.war\WEB-INF\classes\META-INF\ directory . Let me try modifying the session.template and see if that works . I will get back to you after making the changes .


                Thanks again