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ReceiveTaskHandler handling multiple process intances with the same message-id
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created by <a href="http://community.jboss.org/people/mscetin">Melih Cetin</a> in <i>jBPM</i> - <a href="http://community.jboss.org/message/617949#617949">View the full discussion</a>
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<div class="jive-rendered-content"><p>BPMN2 JUnit test for BPMN2-ReceiveTask is implemented as </p><p style="min-height: 8pt; height: 8pt; padding: 0px;"> </p><p style="padding-left: 30px;">ksession.getWorkItemManager().registerWorkItemHandler("Receive Task", receiveTaskHandler);</p><p style="padding-left: 30px;">...</p><p style="padding-left: 30px;">receiveTaskHandler.messageReceived("HelloMessage", "Hello john!");</p><p style="min-height: 8pt; height: 8pt; padding: 0px;"> </p><p>I tried to use ReceiveTaskHandler class in a project to receive a notification from an external system for a specific process-instance and resume the process upon receipt of the message. I could not figure out how to specify the process-instance for which the received message is applicable.</p><p style="min-height: 8pt; height: 8pt; padding: 0px;"> </p><p>JUinit test works fine as there is only one process instance in the session during the execution of this test. The source code for <span style="font-family: courier new,courier;">ReceiveTaskHandler</span> is: </p><p style="min-height: 8pt; height: 8pt; padding: 0px;"> </p><p><span style="font-family: courier new,courier;">public class ReceiveTaskHandler implements WorkItemHandler {</span></p><p>    </p><p><span style="font-family: courier new,courier; color: #000080;">    // TODO: use correlation instead of message id</span></p><p><span style="font-family: courier new,courier;">    private Map<String, Long> waiting = new HashMap<String, Long>();</span></p><p><span style="font-family: courier new,courier;">        ...</span></p><p><span style="font-family: courier new,courier;">    public void executeWorkItem(WorkItem workItem, WorkItemManager manager) {</span></p><p><span style="font-family: courier new,courier;">        String messageId = (String) workItem.getParameter("MessageId");</span></p><p><span style="font-family: courier new,courier;">        waiting.put(messageId, workItem.getId());</span></p><p><span style="color: #000080;"><strong style="font-family: courier new,courier;">        // If waiting map previously contained a mapping for messageId, the old value is replaced !!!</strong></span></p><p><span style="font-family: courier new,courier;">    }</span></p><p>    </p><p><span style="font-family: courier new,courier;">    public void messageReceived(String messageId, Object message) {</span></p><p><span style="font-family: courier new,courier;">        Long workItemId = waiting.get(messageId);</span></p><p><span style="font-family: courier new,courier;">        if (workItemId == null) {</span></p><p><span style="font-family: courier new,courier;">            return;</span></p><p><span style="font-family: courier new,courier;">        }</span></p><p><span style="font-family: courier new,courier;">        Map<String, Object> results = new HashMap<String, Object>();</span></p><p><span style="font-family: courier new,courier;">        results.put("Message", message);</span></p><p><span style="font-family: courier new,courier;">        ksession.getWorkItemManager().completeWorkItem(workItemId, results);</span></p><p><span style="font-family: courier new,courier;">    }</span></p><p><span style="font-family: courier new,courier;">    ...</span></p><p><span style="font-family: courier new,courier;">}</span></p><p style="min-height: 8pt; height: 8pt; padding: 0px;"> </p><p><span style="font-family: arial,helvetica,sans-serif;">The comment of </span><span style="font-family: courier new,courier; color: #000080;">// TODO: use correlation instead of message id </span><span style="font-family: arial,helvetica,sans-serif;">at the top of the source file  also gave the impression that the implementation is not complete. As an interim solution, I decided to extend </span><span style="font-family: courier new,courier;">ReceiveTaskHandler </span><span style="font-family: arial,helvetica,sans-serif;">class as follows:</span></p><p style="min-height: 8pt; height: 8pt; padding: 0px;"> </p><p><span style="font-family: courier new,courier;">public class ReceiveTaskHandler extends org.jbpm.bpmn2.handler.ReceiveTaskHandler {</span></p><p>    </p><p><span style="font-family: courier new,courier;">    private Map<String, Long> waiting = new HashMap<String, Long>();</span></p><p><span style="font-family: courier new,courier;">    private KnowledgeRuntime ksession;</span></p><p style="min-height: 8pt; height: 8pt; padding: 0px;"> </p><p><span style="font-family: courier new,courier;">    public ReceiveTaskHandler(KnowledgeRuntime ksession) {</span></p><p><span style="font-family: courier new,courier;">       super(ksession);</span></p><p><span style="font-family: courier new,courier;">       this.ksession = ksession;</span></p><p><span style="font-family: courier new,courier;">    }</span></p><p style="min-height: 8pt; height: 8pt; padding: 0px;"> </p><p><span style="font-family: courier new,courier;">    private String constructKey(long   processInstanceId, String messageId) {</span></p><p><span style="font-family: courier new,courier;">        return processInstanceId + "|" + messageId;</span></p><p><span style="font-family: courier new,courier;">    }</span></p><p>    </p><p><span style="font-family: courier new,courier;">    @Override</span></p><p><span style="font-family: courier new,courier;">    public void executeWorkItem(WorkItem workItem, WorkItemManager manager) {</span></p><p><span style="font-family: courier new,courier;">        long processInstanceId = workItem.getProcessInstanceId();</span></p><p><span style="font-family: courier new,courier;">        String messageId = (String) workItem.getParameter("MessageId");</span></p><p><span style="font-family: courier new,courier;">        waiting.put(constructKey(processInstanceId, messageId), workItem.getId());</span></p><p><span style="font-family: courier new,courier;">        // If waiting map previously contained a mapping for messageId, the old value is replaced !!!</span></p><p><span style="font-family: courier new,courier;">    }</span></p><p>    </p><p><span style="font-family: courier new,courier;">    @Override</span></p><p><span style="font-family: courier new,courier;">    public void messageReceived(String messageId, Object message) {</span></p><p><span style="font-family: courier new,courier;">        throw new UnsupportedOperationException(</span></p><p><span style="font-family: courier new,courier;">                  "messageReceived(String messageId, Object message) method is not supported. " +</span></p><p><span style="font-family: courier new,courier;">                  "Instead use messageReceived(long, String, Object) method" );</span></p><p><span style="font-family: courier new,courier;">    }</span></p><p>    </p><p><span style="font-family: courier new,courier;">    public void messageReceived(long processInstanceId, String  messageId, Object message) {</span></p><p><span style="font-family: courier new,courier;">        Long workItemId = waiting.get(constructKey(processInstanceId, messageId));</span></p><p><span style="font-family: courier new,courier;">        if (workItemId == null) {</span></p><p><span style="font-family: courier new,courier;">            return;</span></p><p><span style="font-family: courier new,courier;">        }</span></p><p><span style="font-family: courier new,courier;">        Map<String, Object> results = new HashMap<String, Object>();</span></p><p><span style="font-family: courier new,courier;">        results.put("Message", message);</span></p><p><span style="font-family: courier new,courier;">        ksession.getWorkItemManager().completeWorkItem(workItemId, results);</span></p><p><span style="font-family: courier new,courier;">    }</span></p><p><span style="font-family: courier new,courier;">}</span></p><p style="min-height: 8pt; height: 8pt; padding: 0px;"> </p><p><span style="font-family: arial,helvetica,sans-serif;">I was wondering if "Receive Task" is the right task to use for waiting an external notification. If yes, then can any core jBPM </span>contributor <span style="font-family: arial,helvetica,sans-serif;">review the extension that I used locally and consider adding it to the next release of jBPM.</span></p></div>
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