Parsing json without index name in golang

Question

I have a json in the following format

{
    "status_code": 200,
    "status_message": "OK",
    "response": {
        "Messages": [
            "CODE_NOT_AVAILABLE"
        ],
        "UnknownDevices": {
            "": [
                "6",
                "7",
                "8",
                "9",
                "10"
            ]
        }
    }
}

As we see we are missing one index key, after unknownDevices, i am trying to unmarshal this json using golan in the following way

package main

import (
    "encoding/json"
    "fmt"
)

type pushWooshResponse struct {
    Status     int    `json:"status_code"`
    Status_msg string `json:"status_message"`
    Response   response
}

type response struct {
    Message        []string `json:"Messages"`
    UnknownDevices devices
}

type devices struct {
    Udevices []string `json:""`
}

func main() {
    itemInfoR := `{"status_code":200,"status_message":"OK","response":{"Messages":["CODE_NOT_AVAILABLE"],"UnknownDevices":{"devices":["6","7","8","9","10"]}}}`
    itemInfoBytes := []byte(itemInfoR)
    var ItemInfo pushWooshResponse
    er := json.Unmarshal(itemInfoBytes, &ItemInfo)
    if er != nil {
        fmt.Println("Error", er.Error())
    } else {
        fmt.Println(ItemInfo)
    }
}

Output is

{200 OK {[CODE_NOT_AVAILABLE] {[]}}}

Everything is working fine except for the last part, which i am not able to unmarshall this. Can you help me out to umarshal the last part of the json.

Where is this json coming from? Do you really have no control over it? The empty key is just asking for trouble. I would recommend just making UnknownDevices an array instead of an object. — captncraig
– captncraig, Commented Aug 20, 2015 at 16:12
An empty string is a valid key in JSON. Make sure your marshalling method is lossless. Also, in the sample code the empty key is devices instead. Why? — Halcyon
– Halcyon, Commented Aug 20, 2015 at 16:14
In your sample code you have key devices, so you just need to add tag, try this: play.golang.org/p/dACrsAkadN — RoninDev
– RoninDev, Commented Aug 20, 2015 at 16:16
@RoninDev I am asssuming he is stuck with the empty key in the json. If he can change the json it is easy. Unfortunately, it looks to me like encoding/json can marshall empty keys, but for some reason won't unmarshal them. See play.golang.org/p/ut5D5bR16l EDIT: It won't marshal them either. — captncraig
– captncraig, Commented Aug 20, 2015 at 16:19
Some (now deleted) answers changed the type of the Udevices field. Instead you can implement json.Unmarshaller like so: play.golang.org/p/_TMi53hJ3o (you can also implement a custom marshaller). There may be better solutions. — Dave C
– Dave C, Commented Aug 20, 2015 at 16:19

Dave C · Accepted Answer · 2015-08-20 16:28:48Z

5

There may be other options, but whenever you see strange JSON you can always fall back to implementing your own custom (un)marshalling by implementing json.Unmarshaler and/or json.Marshaler.

Perhaps something like:

type devices struct {
    Udevices []string
}

func (d *devices) UnmarshalJSON(b []byte) error {
    var x map[string][]string
    err := json.Unmarshal(b, &x)
    if err == nil {
        // perhaps check that only a single
        // key exists in the map as well
        d.Udevices = x[""]
    }
    return err
}

func (d devices) MarshalJSON() ([]byte, error) {
    x := map[string][]string{"": d.Udevices}
    return json.Marshal(x)
}

Playground

answered Aug 20, 2015 at 16:28

Dave C

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5 Comments

Girish Satyanarayana Over a year ago

When i am trying something like this play.golang.org/p/Zwc9kQBQN9 it does not work, however, the following works, can what am i missing play.golang.org/p/ut5D5bR16l

Dave C Over a year ago

You've changed the structure of the JSON so you need to adjust the unmarshalling to handle that. Your question was about unmarshalling "": …

Girish Satyanarayana Over a year ago

oh ok got it. The reason is I am getting the json as string, so i cannot change it and need to parse it. Sure let me see how i can adjust the unmarshall thanks a lot @Dave

Girish Satyanarayana Over a year ago

Also sorry i sent the wrong code. play.golang.org/p/zmGeFE8o0V the input looks this way. sorry for the confusion

Raul H Over a year ago

What if is only an empty array of strings the "json" response I get how to unmarshall something like this [ "some", "som2", "som3" ]

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