goでjson形式のrequestを受ける

json形式でpostされたhttp requestを処理するサンプル。
今回はpostするjsonのデータ構造を特に決めていないのでパース結果をmap[string]interface{}に保存。

srv.go

package main

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

func dumpJsonRequestHandlerFunc(w http.ResponseWriter, req *http.Request){
  //Validate request
  if req.Method != "POST" {
    w.WriteHeader(http.StatusBadRequest)
    return
  }

  if req.Header.Get("Content-Type") != "application/json" {
    w.WriteHeader(http.StatusBadRequest)
    return
  }

  //To allocate slice for request body
  length, err := strconv.Atoi(req.Header.Get("Content-Length"))
  if err != nil {
    w.WriteHeader(http.StatusInternalServerError)
    return
  }
  
  //Read body data to parse json
  body := make([]byte, length)
  length, err = req.Body.Read(body)
  if err != nil && err != io.EOF {
    w.WriteHeader(http.StatusInternalServerError)
    return
  }
  
  //parse json
  var jsonBody map[string]interface{}
  err = json.Unmarshal(body[:length], &jsonBody)
  if err != nil {
    w.WriteHeader(http.StatusInternalServerError)
    return
  }
  fmt.Printf("%v\n", jsonBody)
  
  w.WriteHeader(http.StatusOK)  
}

func main(){
  http.HandleFunc("/json", dumpJsonRequestHandlerFunc)
  http.ListenAndServe(":8080", nil)
}

json形式のリクエストを受けるサーバを立ち上げる

$go run srv.go

json形式のリクエストをcurlで叩く

$curl -v -H "Content-Type: application/json" -X POST -d '{"integer":1,"string":"xyz", "object": { "element": 1 } , "array": [1, 2, 3]}' http://localhost:8080/json