How to serve up a JSON response using Go?
Question: Currently I'm printing out my response in the func Index
like this fmt.Fprintf(w, string(response))
however, how can I send JSON properly in the request so that it maybe consumed by a view?
package main
import (
"fmt"
"github.com/julienschmidt/httprouter"
"net/http"
"log"
"encoding/json"
)
type Payload struct {
Stuff Data
}
type Data struct {
Fruit Fruits
Veggies Vegetables
}
type Fruits map[string]int
type Vegetables map[string]int
func Index(w http.ResponseWriter, r *http.Request, _ httprouter.Params) {
response, err := getJsonResponse();
if err != nil {
panic(err)
}
fmt.Fprintf(w, string(response))
}
func main() {
router := httprouter.New()
router.GET("/", Index)
log.Fatal(http.ListenAndServe(":8080", router))
}
func getJsonResponse()([]byte, error) {
fruits := make(map[string]int)
fruits["Apples"] = 25
fruits["Oranges"] = 10
vegetables := make(map[string]int)
vegetables["Carrats"] = 10
vegetables["Beets"] = 0
d := Data{fruits, vegetables}
p := Payload{d}
return json.MarshalIndent(p, "", " ")
}
Solution 1:
You can set your content-type header so clients know to expect json
w.Header().Set("Content-Type", "application/json")
Another way to marshal a struct to json is to build an encoder using the http.ResponseWriter
// get a payload p := Payload{d}
json.NewEncoder(w).Encode(p)
Solution 2:
Other users were commenting that the Content-Type
is plain/text
when encoding.
You have to set the content type with w.Header().Set()
first, then write the HTTP response code with w.WriteHeader()
.
If you call w.WriteHeader()
first, then call w.Header().Set()
after you will get plain/text
.
An example handler might look like this:
func SomeHandler(w http.ResponseWriter, r *http.Request) {
data := SomeStruct{}
w.Header().Set("Content-Type", "application/json")
w.WriteHeader(http.StatusCreated)
json.NewEncoder(w).Encode(data)
}
Solution 3:
You can do something like this in you getJsonResponse
function -
jData, err := json.Marshal(Data)
if err != nil {
// handle error
}
w.Header().Set("Content-Type", "application/json")
w.Write(jData)