About 3 years into programming what’s next

So I’ve been a java developer for about 3 years, I just got promoted, I do a lot of development in older java programs, including .jsp, and servlets,I dabble in spring development and handle a lot of the front end applications, working with lots of older JavaScript ect. I’d like to take my self to the next level on my own time and make myself more valuable. Is there a class or certification you’d recommend early mid level developers should take?