Getting IssueValidator cannot be cast to com.opensymphony.workflow.loader.ValidateDescriptor Excepti

[Himanshu Agarwal]

Hello,
My requirement is add workflow validator programmatically. I have created a workflow validator using https://www.j-tricks.com/tutorials/workflow-validator.
Now i am getting below exception.

IssueValidator cannot be cast to com.opensymphony.workflow.loader.ValidateDescriptor

I am using below code for creating validator.

public class IssueValidatorFactory extends AbstractWorkflowPluginFactory implements WorkflowPluginValidatorFactory {

    @Override
    protected void getVelocityParamsForInput(Map<String, Object> map) {
    }

    @Override
    protected void getVelocityParamsForEdit(Map<String, Object> map, AbstractDescriptor abstractDescriptor) {
    }

    @Override
    protected void getVelocityParamsForView(Map<String, Object> map, AbstractDescriptor abstractDescriptor) {
    }

    @Override
    public Map<String, ?> getDescriptorParams(Map<String, Object> map) {
        return map;
    }

}

public class IssueValidator implements Validator {

    private final ScheduleManager scheduleManager;

    public IssueValidator(ScheduleManager scheduleManager) {
        this.scheduleManager = scheduleManager;
    }

    public void validate(Map transientVars, Map args, PropertySet ps) throws InvalidInputException, WorkflowException {
        Issue issue = (Issue) transientVars.get("issue");
        List<Schedule> schedules =  scheduleManager.getSchedulesByExecutionStatus(String.valueOf(ApplicationConstants.JOB_STATUS_FAILED), issue.getId().intValue());
        if (!schedules.isEmpty()){
            throw new InvalidInputException("You can't set done status of this issue because " + schedules.size() + " execution is in fail conditions.");
        }

    }
}

Using below code for add validator programmatically.

WorkflowManager workflowManager = ComponentAccessor.getWorkflowManager();

JiraWorkflow workflow = workflowManager.getWorkflow(projectEvent.getProject().getId(),
        JiraUtil.getTestcaseIssueTypeId());
JiraWorkflow draftWorkflow =
        workflowManager.createDraftWorkflow(projectEvent.getUser(), workflow.getName());
Collection<ActionDescriptor> actionDescriptors = workflow.getActionsByName("Done");
for(ActionDescriptor actionDescriptor : actionDescriptors){
    actionDescriptor.getValidators().add(new IssueValidator(scheduleManager));
}
workflowManager.updateWorkflow(projectEvent.getUser(), draftWorkflow);

Please help me out of this problem.