How to access fields of a JSON in GO

Question

Hi everyone I'm trying to see what the proper way of accessing fields of a json object from a http.get request in go.

I first do an http.get call get the JSON and then print it (which works) but is there a way to access just a field?

for example:

response, err:= http.Get("URL")
//Error checking is done between
contents, err:=ioutil.Readall(response.Body)

//Now at this point I have a json that looks like
{"id": "someID", 
"name": "someName", 
"test": [{"Name":"Test1", 
          "Result": "Success"},
         {"Name":"Test2", 
          "Result": "Success"},
         {...},
]}

Is there a way to only print the "test" of the Json? What is the proper way of accessing that field?

you will have to parse json using encoding/json package.

sfault
– sfault

2016-02-26 19:52:29 +00:00
Commented Feb 26, 2016 at 19:52 — sfault
– sfault, Commented Feb 26, 2016 at 19:52

sfault · Accepted Answer · 2016-02-26 19:58:57Z

17

Use encoding/json package to Unmarshal data into struct, like following.

type Result struct {
    ID   string        `json:"id"`
    Name string        `json:"name"`
    Test []interface{} `json:"test"`
}

var result Result
json.Unmarshal(contents, &result)
fmt.Println(result.Test)

You can also parse Test to specific struct.

edited Feb 26, 2016 at 19:58

answered Feb 26, 2016 at 19:57

sfault

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3 Comments

Nighthee Over a year ago

Ohhh I see, what did you mean parse Test to a specific struct?

sfault Over a year ago

You can define a struct named Test and in Result struct use Test []Test instead of Test []interface{}

psq Over a year ago

Struct fields that have a json tag (all of them, in the example proposed here) need to be exported, meaning they need to start with a capital letter. More info at Exported identifiers

PlutoShe · Accepted Answer · 2016-02-27 02:58:33Z

14

Same as the previous answer, use encoding/json package to Unmarshal data. But if you don't want to specify the structure, you could use map[string]interface/bson.M{} to receive the data, and get the field, then cast into types your want.

m := make(map[string]interface{})
err := json.Unmarshal(data, &m)
if err != nil {
    log.Fatal(err)
}
fmt.Println(m["id"])

answered Feb 27, 2016 at 2:58

PlutoShe

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Comments

deepak · Accepted Answer · 2016-02-27 14:53:15Z

3

You may want to try gabs container, if you are not sure how depth JSON hierarchy can be. Have a look at below resources

https://github.com/Jeffail/gabs https://godoc.org/github.com/Jeffail/gabs

answered Feb 27, 2016 at 14:53

deepak

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Comments

James Matheson · Accepted Answer · 2018-09-29 09:52:01Z

2

If you just want to access one field then you can use the jsonq module https://godoc.org/github.com/jmoiron/jsonq

For your example you could get the test object with code similar to

jq.Object("test")

Where jq is a jsonq query object constructed from your JSON above (see the godoc page for instructions on how to create a query object from a JSON stream or string).

You can also use this library for retrieving specific String, Integer, Float and Bool values at an arbitrary depth inside a JSON object.

answered Sep 29, 2018 at 9:52

James Matheson

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Brachi · Accepted Answer · 2022-05-30 11:55:56Z

1

You may check this https://github.com/valyala/fastjson

s := []byte(`{"foo": [123, "bar"]}`)
    fmt.Printf("foo.0=%d\n", fastjson.GetInt(s, "foo", "0"))

    // Output:
    // foo.0=123

answered May 30, 2022 at 11:55

Brachi

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Comments

Zombo · Accepted Answer · 2021-05-28 22:43:46Z

0

Since you are starting with a URL, Decode is a better option than Unmarshal:

package main

import (
   "encoding/json"
   "net/http"
)

func main() {
   r, e := http.Get("https://github.com/manifest.json")
   if e != nil {
      panic(e)
   }
   defer r.Body.Close()
   var s struct { Name string }
   json.NewDecoder(r.Body).Decode(&s)
   println(s.Name == "GitHub")
}

https://golang.org/pkg/encoding/json#Decoder.Decode

answered May 28, 2021 at 22:43

Zombo

1

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