I'm a junior developer at a small company(about 50 employees) that specializes in a very niche technology. Since there are very few companies using this technology I'm really concerned about my future and I decided to switch to Java development.
My current job contract ends on May 31 and I got myself a job offer as a Junior Java Developer from a very respectable company, starting on June 1. What I'm struggling with is explaining to my employer why I dont want to stay at my current company. He's willing to accomodate all of my needs, i.e. switching me to Java projects(our Java devs barely got anything to do lately, but he says that big contracts are coming soon), he will allow me to work remotely more often, I will get a really big raise, and some other things. The thing is, except for the big raise, I dont trust that he will follow with his promises and I'll probably end up in the same niche technology that I want to leave.
EDIT: Sorry for the confusion. The thing is, I already told him that Im leaving but he's now doing everything he can to keep me.