I use these two options:
- Override you ApplicationRootUrl in your Custom Settings so you use the java action you mentioned (GetApplicationURL):
to set in the modeler:
Second option ( I use the most):
Create a constant in your module and set it with your custom url. You can use the constant everywhere in your model after that.
This questions explains what the getApplicationurl java action is doing
To pass this value as a string, I think you might need to create a non persistent entity with an attribute as a string.