Problem with simple workflow

[gm]

I'm trying to write simple workflow and run it on Alfresco Share.
these are workflow definition and context files:

simpleTask.bpmn
<blockcode>
<?xml version="1.0" encoding="UTF-8"?>
<definitions
    xmlns="http://www.omg.org/spec/BPMN/20100524/MODEL"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xmlns:activiti="http://activiti.org/bpmn"
    typeLanguage="http://www.w3.org/2001/XMLSchema"
    expressionLanguage="http://www.w3.org/1999/XPath"
    targetNamespace="http://www.activiti.org/test">

    <process id="simpleProcess" name="Simple Workflow" isExecutable="true">
        <startEvent id="eventStart" name="Start"></startEvent>
        <userTask id="simpleTask" name="Simple Task" activiti:assignee="admin" activiti:formKey="bpm:workflowTask"></userTask>
        <endEvent id="eventEnd" name="End"></endEvent>
        <sequenceFlow id="flow1" sourceRef="eventStart" targetRef="simpleTask"></sequenceFlow>
        <sequenceFlow id="flow2" sourceRef="simpleTask" targetRef="eventEnd"></sequenceFlow>
    </process>
</definitions>

</blockcode>

simpleTas-workflow-context.xml

<?xml version='1.0' encoding='UTF-8'?><!DOCTYPE beans PUBLIC '-//SPRING//DTD BEAN//EN' 'http://www.springframework.org/dtd/spring-beans.dtd'><beans>    <bean id="wf-simpleTask" parent="workflowDeployer">        <property name="workflowDefinitions">            <list>                <props>                    <prop key="engineId">activiti</prop>                    <prop key="location">alfresco/extension/simpleTask.bpmn</prop>                    <prop key="mimetype">text/xml</prop>                    <prop key="redeploy">false</prop>                </props>            </list>        </property>        <property name="models">            <list>                <value>alfresco/model/bpmModel.xml</value>            </list>        </property>    </bean></beans>‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍

I have deployed it. No errors are shown in alfresco log files.

In the Alfresco Share workflow shows in "Start Workflow" menu, but when I try to start it, "Failure - Workflow could not be started" error message pops up .

this is the exception that gets logged in share.log/catalina.log files:

10:56:56,796 ERROR [org.springframework.extensions.webscripts.AbstractRuntime] Exception from executeScript - redirecting toorg.springframework.extensions.webscripts.WebScriptException: 01130000 Wrapped Exception (with status template): null        at org.springframework.extensions.webscripts.AbstractWebScript.createStatusException(AbstractWebScript.java:1067)        at org.springframework.extensions.webscripts.DeclarativeWebScript.execute(DeclarativeWebScript.java:171)        at org.springframework.extensions.webscripts.PresentationContainer.executeScript(PresentationContainer.java:70)        at org.springframework.extensions.webscripts.LocalWebScriptRuntimeContainer.executeScript(LocalWebScriptRuntimeContai        at org.springframework.extensions.webscripts.AbstractRuntime.executeScript(AbstractRuntime.java:377)        at org.springframework.extensions.webscripts.AbstractRuntime.executeScript(AbstractRuntime.java:209)        at org.springframework.extensions.webscripts.servlet.mvc.WebScriptView.renderMergedOutputModel(WebScriptView.java:104        at org.springframework.web.servlet.view.AbstractView.render(AbstractView.java:250)        at org.springframework.web.servlet.DispatcherServlet.render(DispatcherServlet.java:1047)        at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:817)        at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:719)        at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:644)        at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:549)        at javax.servlet.http.HttpServlet.service(HttpServlet.java:621)        at javax.servlet.http.HttpServlet.service(HttpServlet.java:722)        at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:305)        at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)        at org.apache.catalina.core.ApplicationDispatcher.invoke(ApplicationDispatcher.java:749)        at org.apache.catalina.core.ApplicationDispatcher.processRequest(ApplicationDispatcher.java:487)        at org.apache.catalina.core.ApplicationDispatcher.doForward(ApplicationDispatcher.java:412)        at org.apache.catalina.core.ApplicationDispatcher.forward(ApplicationDispatcher.java:339)        at org.tuckey.web.filters.urlrewrite.NormalRewrittenUrl.doRewrite(NormalRewrittenUrl.java:195)        at org.tuckey.web.filters.urlrewrite.RuleChain.handleRewrite(RuleChain.java:159)        at org.tuckey.web.filters.urlrewrite.RuleChain.doRules(RuleChain.java:141)        at org.tuckey.web.filters.urlrewrite.UrlRewriter.processRequest(UrlRewriter.java:90)        at org.tuckey.web.filters.urlrewrite.UrlRewriteFilter.doFilter(UrlRewriteFilter.java:417)        at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:243)        at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)        at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:222)        at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:123)        at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:472)        at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:168)        at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:99)        at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:929)        at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:118)        at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:407)        at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1002)        at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:585)        at org.apache.tomcat.util.net.AprEndpoint$SocketProcessor.run(AprEndpoint.java:1813)        at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1110)        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:603)        at java.lang.Thread.run(Thread.java:722)Caused by: java.lang.NullPointerException        at org.alfresco.web.scripts.forms.FormUIGet.processFieldConstraintControl(FormUIGet.java:1956)        at org.alfresco.web.scripts.forms.FormUIGet.generateConstraintModel(FormUIGet.java:1816)        at org.alfresco.web.scripts.forms.FormUIGet.processFieldConstraints(FormUIGet.java:1701)        at org.alfresco.web.scripts.forms.FormUIGet.generateFieldModel(FormUIGet.java:1315)        at org.alfresco.web.scripts.forms.FormUIGet.generateDefaultSetModelUsingServerFields(FormUIGet.java:1255)        at org.alfresco.web.scripts.forms.FormUIGet.processServerFields(FormUIGet.java:1117)        at org.alfresco.web.scripts.forms.FormUIGet.processFields(FormUIGet.java:1058)        at org.alfresco.web.scripts.forms.FormUIGet.generateFormUIModel(FormUIGet.java:666)        at org.alfresco.web.scripts.forms.FormUIGet.generateFormModel(FormUIGet.java:609)        at org.alfresco.web.scripts.forms.FormUIGet.generateModel(FormUIGet.java:265)        at org.alfresco.web.scripts.forms.FormUIGet.executeImpl(FormUIGet.java:220)        at org.springframework.extensions.webscripts.DeclarativeWebScript.execute(DeclarativeWebScript.java:64)        … 40 more‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍

So, where is the problem here?
Thank you

[ashpal19]

Can you please change the redeploy property to true(simpleTas-workflow-context.xml) and try again.

You will keep getting an older error until you set redeploy to true. 

[gm]

done that.
only thing that changed is error code in share.log file:
WebScriptException code is now 01140000, otherwise same exception with same stack trace

[ashpal19]

Another thing which I noticed is activiti:formKey="bpm:workflowTask". I do not think you can have a bpm:xxx as the formkey. You will need to use something like -  wf:activitiReviewTask or something equivalent as the formkey. Or if you have defined your own custom model, you can use that.

[gm]

tried that too.
same error with same exception trace

[gm]

to answer my own question.

this problem is version specific. after upgrading alfresco from 4.2.c to 4.2.e problem resolved.

found related thread about this problem:
http://forums.alfresco.com/forum/developer-discussions/workflow/cant-run-activiti-wf-alfresco-42c-nu...