How to distribute threads between java servlets?

Question

Java

There is a project logically divided into several java servlets. What is the most natural way to control the number of threads used by servlets?

It is required, for example, to give at least one thread for the return of statics, for servlet No. 2 at least 8, and for servlet No. 3 all the remaining ones. But at the same time, servlet #3 cannot be allowed to gobble up all available resources.