How to serve up a JSON response using Go

Question

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

User · Accepted Answer

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)

User · Answer

You may use this package renderer  I have written to solve this kind of problem  it s a wrapper to serve JSON  JSONP  XML  HTML etc

User · Answer

In gobuffalo io framework I got it to work like this      say we are in some resource Show action    some code is omitted user     amp models User   if c Request   Header Get  Content-type       application json        return c Render 200  r JSON user     else          Make user available inside the html template     c Set  user   user      return c Render 200  r HTML  users show html        and then when I want to get JSON response for that resource I have to set  Content-type  to  application json  and it works   I think Rails has more convenient way to handle multiple response types  I didn t see the same in gobuffalo so far

User · Answer

Other users commenting that the Content-Type is plain text when encoding  You have to set the Content-Type first w Header   Set  then the HTTP response code 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

User · Answer

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

[json] How to serve up a JSON response using Go?

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