I start a flow, then i can get the formKey of this user task, but the form properties is null.
probably you need to query form engine for form by formKey, not the task itself.
thanks, i resolved it by
Form Properties are the old way of attaching fields to task. If you use the flowable forms to attach fields to user task, then you will get formProperties Null because these properties no longer attached to user task but a seperate form is attached (by form key) and then you have to query the form to get all the fields. You can do something like this to get form and its properties attached to task.
Map<String, FormField> formFields = taskService.getTaskFormModel(“taskId”)
Now, You can iterate over this map keys to get FormField Class Object for each Field key and get its properties from here.
Hope this helps.