Does it make any sense to use the servlet scopes outside of a servlet?

[Hannes Steffenhagen]

Hello, I'm currently writing an Application using Guice. It is not a web application (nor is it based on servlets), but it still conceptually has scopes like 'Application', 'Session' and 'Request' - does it make any sense at all to try to attempt to use the built in scopes from the web module? Or should I rather write my own scopes, despite what the documentation recommends?

[Jens]

The session scope stores data in the HTTP session and the request scope stores data as attribute on the HTTP servlet request. See: https://github.com/google/guice/blob/master/extensions/servlet/src/com/google/inject/servlet/ServletScopes.java

So if you don't have a HttpSession and HttpServletRequest in your application then you can not use these scopes.

-- J.

[Hannes Steffenhagen]

I see. I guess the documentation saying that it's not recommended for users to write their own scopes made me thing the built in scopes were more general than they actually are.

[Tim Boudreau]

On Sunday, June 7, 2015 at 3:12:08 PM UTC-4, Hannes Steffenhagen wrote:

Hello, I'm currently writing an Application using Guice. It is not a web application (nor is it based on servlets), but it still conceptually has scopes like 'Application', 'Session' and 'Request' - does it make any sense at all to try to attempt to use the built in scopes from the web module? Or should I rather write my own scopes, despite what the documentation recommends?

I've found it so useful to do that that I wrote a library for generically doing custom scopes:

https://github.com/timboudreau/scopes

To use it in a Maven project:

http://timboudreau.com/builds/

(one of these days I'll get that and a bunch of related stuff on Maven Central)

-Tim

 

[Luke Sandberg]

I work on servers that have 'extended' the definition of @RequestScope beyond just servlet based http requests.  We use the same annotations but use alternate implementations of the Scope object.  So i think it would be quite reasonable to reimplement the scopes for your usecase.

The general advice around 'don't implement your own scopes' is accurate,  a Scope is generally a very general and all encompassing concept, so it is rare that you might have an application that needs something beyond the standard set.  Plus there can be weird issues introduced if your custom scopes have overlapping lifetimes.  So the advice is correct, it just may not apply to your usecase :)

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