How do I parse a JSON string in Golang?

Question

Given a URL like the following.

http://127.0.0.1:3001/find?field=hostname&field=App&filters=["hostname":"example.com,"type":"vm"]

How do I extract JSON values corresponding to keys for eg: hostname 'example.com' and type 'vm'.

I am trying

filters := r.URL.Query()["filters"]

which gives following output:

[["hostname":"example.com,"type":"vm"]]

Instead of trying to directly access the map from key to values diirectly, you probably mean to use Request.FormValue instead. golang.org/pkg/net/http/#Request.FormValue — dyoo
– dyoo, Commented Jan 19, 2015 at 0:12

score 4 · Accepted Answer · 2015-01-19 01:21:18Z

4

Use the encoding/json package to parse JSON. The query string in the example URL does not contain valid JSON.

Here's an example show how to use the JSON parser on a slightly different URL.

s := `http://127.0.0.1:3001/find?field=hostname&field=App&filters={"hostname":"example.com","type":"vm"}`
u, err := url.Parse(s)
if err != nil {
    log.Fatal(err)
}
var v map[string]string
err = json.Unmarshal([]byte(u.Query().Get("filters")), &v)
if err != nil {
    log.Fatal(err)
}
fmt.Println(v)

playground example

edited Jan 19, 2015 at 1:21

answered Jan 18, 2015 at 18:11

user5728991

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1 Comment

dyoo Over a year ago

The example "string" the question presents isn't even a string, technically. By using r.URL.Query(), they have a value of type map[string][]string (golang.org/pkg/net/url/#Values). So what the question is presenting isn't technically accurate: they're should be getting back a list with a single string. They probably did a simple fmt.Println(filters) on the value, rather than an output statement that presents more literal output, such as fmt.Printf("%#v\n", filters).

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