Correct way to pass multiple values for same parameter name in GET request

Question

I m looking into what is the correct way to pass multiple values for the same parameter name in a GET request   I ve seen URLs like this   http   server action id a amp id b   And I ve seen URLs like this   http   server action id a b   My understanding is that the first is correct  but I can t find any reference for this  I had a look at the http spec but couldn t see anything about how the  query  part of a URL should be made up   I don t want an answer that says  either is fine  - if I m building a webservice  I want to know which of these methods is standard so that people using my webservice know how to pass multiple parameters for the same name   So  can someone point me at an official reference source to confirm which option is correct

User · Answer

I am describing a simple method which worked very smoothly in Python (Django Framework).

1. While sending the request, send the request like this

http://server/action?id=a,b

2. Now in my backend, I split the value received with a split function which always creates a list.

id_filter = id.split(',')

Example: So if I send two values in the request,

http://server/action?id=a,b

then the filter on the data is

id_filter = ['a', 'b']

If I send only one value in the request,

http://server/action?id=a

then the filter outcome is

id_filter = ['a']

3. To actually filter the data, I simply use the 'in' function

queryset = queryset.filter(model_id__in=id_filter)

which roughly speaking performs the SQL equivalent of

WHERE model_id IN ('a', 'b')

with the first request and,

WHERE model_id IN ('a')

with the second request.

This would work with more than 2 parameter values in the request as well !

User · Answer

there is no standard  but most frameworks support both  you can see for example for java spring that it accepts both here  GetMapping  quot  api foos quot    ResponseBody public String getFoos  RequestParam List lt String gt  id        return  quot IDs are  quot    id     And Spring MVC will map a comma-delimited  id  parameter  http   localhost 8080 api foos id 1 2 3 ---- IDs are  1 2 3   Or a list of separate id parameters  http   localhost 8080 api foos id 1 amp id 2 ---- IDs are  1 2

User · Answer

Indeed  there is no defined standard  To support that information  have a look at wikipedia  in the Query String chapter  There is the following comment      While there is no definitive standard  most web frameworks allow   multiple values to be associated with a single field  3  4    Furthermore  when you take a look at the RFC 3986  in section 3 4 Query  there is no definition for parameters with multiple values    Most applications use the first option you have shown  http   server action id a amp id b  To support that information  take a look at this Stackoverflow link  and this MSDN link regarding ASP NET applications  which use the same standard for parameters with multiple values   However  since you are developing the APIs  I suggest you to do what is the easiest for you  since the caller of the API will not have much trouble creating the query string

User · Answer

Solutions above didn t work  It simply displayed the last key value pairs  but this did   http   localhost  key   1 amp key   2  Returns  Array    key    gt  Array                0    gt  1          1    gt  2

User · Answer

I would suggest looking at how browsers handle forms by default  For example take a look at the form element  lt select multiple gt  and how it handles multiple values from this example at w3schools    lt form action   action page php  gt   lt select name  cars  multiple gt     lt option value  volvo  gt Volvo lt  option gt     lt option value  saab  gt Saab lt  option gt     lt option value  opel  gt Opel lt  option gt     lt option value  audi  gt Audi lt  option gt   lt  select gt   lt input type  submit  gt   lt  form gt    For PHP use    lt select name  cars    multiple gt    Live example from above at w3schools com  From above if you click  saab  opel  and click submit  it will generate a result of cars saab amp cars opel  Then depending on the back-end server  the parameter cars should come across as an array that you can further process    Hope this helps anyone looking for a more  standard  way of handling this issue

[http] Correct way to pass multiple values for same parameter name in GET request

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