IWS, REST and retrieving variables from QUERY_STRING

Hi All,

I'm creating a REST webservice/api and using IWS. I'm then using Postman
to test the webservice. All the endpoints call procedures in a service
program..

I have an endpoint /web/server/claims which will call the RPG procedure
GetAllClaims which returns all claims. I have tested this with Postman
and it works correctly.

My next step is to add a filter. So I call the same endpoint but this time
I pass a parameter of whid. So the endpoint now becomes
/web/server/claims/?whid=93 which will call the RPG procedure GetAllClaims
but this time I need to extract the parameter passed in the QUERY_STRING to
return only claims for warehouse 93.

Can someone point me to either documentation or an example of how to
specify and extract from the QUERY_STRING. I've done a lot of searching on
Google but I must not be searching on the correct terms because I can't
find anything on QUERY_STRING other than that you may specify it..

Thanks,

Rob