How to get current assignee information of Human Task

Hi all,

Currently, I try to design the process with a human task with have timer trigger to catch if over 1 hour, the assignee doesn't have action, the system will send notification by email.

But I don't know the way to get assignee information. I try to use the code script below (Exercise 7 in Bonita Camp):

#########################################################################
def processApi = apiAccessor.getProcessAPI();
def identityApi = apiAccessor.getIdentityAPI();

//Get the TaskInstance
def humanTaskInstance = processApi.getHumanTaskInstances(processInstanceId, "Validate request", 0, 1).get(0);

//Get the user id assigned to the task review request
def reviewRequestAssignedId = humanTaskInstance.getAssigneeId();

//Get the review request email
String reviewRequestAssignedEmail = "";

if(reviewRequestAssignedId >0){
   reviewRequestAssignedEmail = identityApi.getUserContactData(reviewRequestAssignedId, false).getEmail();
}
else{
   reviewRequestAssignedEmail = "william.jobs@acme.com"
}
return reviewRequestAssignedEmail;

###################################################################

But reviewRequestAssignedId always return 0.

Pls, help me the right way.

Thanks so much for all your support !!!