Question

I’ve create a servlet to let me know if the webapp inside a Tomcat container is running or not. But now, I’m wondering if it is possible that one servlet responds and not another one? i.e. can two independent servlets (in the same webapp) be independently responsive or can I assume if one responds the other will respond?

Something that gives some clues but not enough information.

Useful source

Thank you

Answer 1

Is a servlet independent from another (process wise)?

Yes. The Servlet 3.0 spec tells among others the following:

2.3.2.1 Error Conditions on Initialization

During initialization, the servlet instance can throw an UnavailableException or a
ServletException. In this case, the servlet must not be placed into active service
and must be released by the servlet container. The destroy method is not called as it
is considered unsuccessful initialization.

It doesn’t say any line about that the other servlets should not be initialized or something. Just that the servlet is not been placed into active service.

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Update as per the comments: the same spec tells the following whenever a successfully initialized servlet throws an exception during the service:

2.3.3.2 Exceptions During Request Handling

A servlet may throw either a ServletException or an UnavailableException
during the service of a request. A ServletException signals that some error
occurred during the processing of the request and that the container should take
appropriate measures to clean up the request.

An UnavailableException signals that the servlet is unable to handle requests
either temporarily or permanently. If a permanent unavailability is indicated by the UnavailableException, the servlet container must remove the servlet from service, call its destroy method, and release the servlet instance. Any requests refused by the container by that cause must be returned with a SC_NOT_FOUND (404) response.