How to identify clicked  Bpm outcome button ?

Hi, Dharmraj Gurjar

you can execute your script based on the outcome button click
refer this example

<userTask id="reviewTask" name="Review Task" activiti:assignee="${bpm_assignee.properties.userName}" activiti:formKey="wf:activitiReviewTask">
      <extensionElements>
         <activiti:taskListener event="complete" class="org.alfresco.repo.workflow.activiti.tasklistener.ScriptTaskListener">
          <activiti:field name="script">
            <activiti:string><![CDATA[
//getting your task outcome , you can get the outcome button value by using this
// wf_reviewOutcome your modelPrefix_outcomeProperty 
task.getVariable('wf_reviewOutcome');
                ]]></activiti:string>
          </activiti:field>
        </activiti:taskListener>
      </extensionElements>
    </userTask>

Thanks,
Kalpesh,
ContCentric