I want to create a system where I send email to the assigned user if they have an incomplete task nearing its due date. Where should I put the codes for it in the Engines? Or is it impossible with Activiti and I'm better off using another programming language (PHP comes to mind)? Thanks!
Of course it's possible. A simple sql query on act_ru_task allow you to list tasks nearing due date. Otherwise you could use the activiti java API to create a batch that can do that.