Golang : Unmarshal JSON from http response

For this tutorial, we will learn how to unmarshal JSON data retrieved from http.Get() function. Using the HTTP response JSON data tutorial as example, the codes below will grab the JSON data and unmarshal them into struct.

NOTE : This example is also useful ... as a way for you to mock JSON reply to test your API.

The first part, will be the server generating the JSON data. Simple program with static JSON response :

jsonresponse.go

 package main

 import (
 "net/http"
 )

 func Employees(w http.ResponseWriter, r *http.Request) {
 w.Header().Set("Content-Type", "application/json")

 jsonStr := `[{"Name":"Adam","Age":36,"Job":"CEO"},
  {"Name":"Eve","Age":34,"Job":"CFO"},
  {"Name":"Mike","Age":38,"Job":"COO"}]`

 w.Write([]byte(jsonStr))
 }

 func main() {
 // http.Handler

 mux := http.NewServeMux()
 mux.HandleFunc("/employees", Employees)

 http.ListenAndServe(":8080", mux)
 }

build this program and run it at the background.

Point your browser to http://127.0.0.1:8080/employees should give you this reply

 [{"Name":"Adam","Age":36,"Job":"CEO"},
  {"Name":"Eve","Age":34,"Job":"CFO"},
  {"Name":"Mike","Age":38,"Job":"COO"}] 

this part will be the client requesting the JSON data and convert it into a struct :

processjsonresponse.go

 package main

 import (
 "encoding/json"
 "fmt"
 "io/ioutil"
 "net/http"
 )

 type Employee struct {
 Name string
 Age  int
 Job  string
 }

 func main() {

 // url will return
 // [
 // {"Name":"Adam","Age":36,"Job":"CEO"},
 // {"Name":"Eve","Age":34,"Job":"CFO"},
 // {"Name":"Mike","Age":38,"Job":"COO"}
 // ]

 url := "http://127.0.0.1:8080/employees"

 resp, err := http.Get(url)

 defer resp.Body.Close()

 if err != nil {
 panic(err)
 }

 // read json http response
 jsonDataFromHttp, err := ioutil.ReadAll(resp.Body)

 if err != nil {
 panic(err)
 }


 var jsonData []Employee

 err = json.Unmarshal([]byte(jsonDataFromHttp), &jsonData) // here!

 if err != nil {
 panic(err)
 }

 // test struct data
 fmt.Println(jsonData)

 }

If everything goes well, executing processjsonresponse.go should give you this line :

[{Adam 36 CEO} {Eve 34 CFO} {Mike 38 COO}]

Useful link : http://jsonlint.com/ - to verify is the JSON result is valid or not.

Reference :

Golang HTTP Get example