How to monitor Executors or other Task Executing Threads in Spring MVC

How to monitor Executors or other Task Executing Threads in Spring MVC

I am creating a web application and in this I will be creating many
services and executors to do some tasks.I have extended dispacter servlet
and started executors or other threads in init method.Is this the right
approach?
Now Suppose if any request comes and that executor or similar task
executing thread dies after throwing Exception.
1.I suppose that it will affect other requests also.So what shall I do in
such cases?
2.How can I create a monitor thread which will check if all critial tasks
executing thread and executors are properly running?
3.Should I keep another backup executor prepared and deferred to takeover
the failed executor in such situations?If so then how?