How can i use external URL form for human task with bonita 7

Hello,

I want to use external form instead of UIDesigner form for human task. For my test i create a simple test with one human task and i write in the human task -> form -> URL : "www.google.com"

When i launch the process and come to this form i get an Error 500.

Do you know how i can use external form ? or where i can find documentation about it for bonita 7 ?

Thanks