Go GIN context parse unexpected query string

Question

I have different structs for the query in the REST request. I'd like to return HTTP 400: BAD REQUEST when the query string contains an unexpected parameter than my struct.

type FilterData struct {
    Filter1 string `form:"filter_1"`
    Filter2 string `form:"filter_2"`
    Filter3 string `form:"filter_3"`
}

The expected request request is localhost:8000/testing?filter_1=123456&filter_2=test&filter_3=golang

But if the is request like localhost:8000/users?FILTER1=123456&filter_2=test&filter_3=golang or any extra parameter than my expected struct I want to return bad request.

Go gin.Context has c.ShouldBindQuery(&filterData) but this returns the filter_1 as an empty string, indeed in my case that's a bad request.

How would I do an extra check with a common function to all requests?

PS. some values in this struct can be optional.

potato_cannon · Accepted Answer · 2022-03-16 22:33:27Z

1

It is pretty standard in apis to ignore unknown query parameters. If you require some parameters to always have value, use binding:"required" property in your struct tags.

https://github.com/gin-gonic/gin#model-binding-and-validation

If you want to throw back a 400 on unknown query params, you must check contents of c.Request.URL.Query().

edited Mar 16, 2022 at 22:33

answered Mar 16, 2022 at 21:08

potato_cannon

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2 Comments

Taylan Yuksel Over a year ago

c.Request.URL.Query() returns map[string][]string like given in this answer. when I loop through these keys, how can I compare that is the string in my struct?

potato_cannon Over a year ago

You have already hardcoded the valid parameters on your struct. Just check each key on the query map against a list of valid keys. If any key in the query map is not one of filter_1, filter_2 or filter_3, you can hit back that 400. If you want something general, you have to take a look at reflect package. Figure out a way to get struct fields and check query keys against valid fields that way.

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