Simple HTTP handler wrapper for conveniently dealing with JSON requests

jsonhandler.go

// JSONResponseWriter wraps an http.ResponseWriter and provides convenience methods for creating JSON responses
type JSONResponseWriter struct {
        writer http.ResponseWriter
}

// Response writes an HTTP response with the value v encoded in JSON format.
func (w JSONResponseWriter) Response(v interface{}) {
        w.writer.Header().Set("Content-Type", "application/json")
        enc := json.NewEncoder(w.writer)
        enc.Encode(v)
}

// Response returns an HTTP response with the given status code and a message encoded in JSON format.
// The format and args arguments are analagous to those in fmt.Printf. The resulting JSON is an object with
// a single field "error", eg:
//
//              {"error": "some message"}
//
func (w JSONResponseWriter) Error(code int, format string, args ...interface{}) {
        type Error struct {
                Error string `json:"error"`
        }
        w.writer.Header().Set("Content-Type", "application/json")
        msg := Error{fmt.Sprintf(format, args...)}
        w.writer.WriteHeader(code)
        enc := json.NewEncoder(w.writer)
        // Nothing we can do about errors at this point, so ignore them
        enc.Encode(msg)
}

// JSONRequest is a wrapper around http.Request that provides additional methods for dealing with requests
// that contain JSON-encoded content
type JSONRequest struct {
        *http.Request
}

// Decode reads the JSON-encoded value from the request body and stores it in the value pointed to by v.
func (r JSONRequest) Decode(v interface{}) error {
        dec := json.NewDecoder(r.Body)
        return dec.Decode(v)
}

// JSONHandler is a type of handler for JSON-encoded HTTP requests
type JSONHandler func(w JSONResponseWriter, r JSONRequest)

func (h JSONHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
        h(JSONResponseWriter{w}, JSONRequest{r})
}