golang request.ParseForm（）是否与“ application / json”内容类型一起使用

Question

Using a simple HTTP server in Go (1.4), the request form is empty if content-type is set to "application/json". Is this intended?

The simple http handler:

func (s Server) ServeHTTP(w http.ResponseWriter, r *http.Request) {
    r.ParseForm()
    log.Println(r.Form)
}

For this curl request, the handler prints the correct form values:

curl -d '{"foo":"bar"}' http://localhost:3000
prints: map[foo:[bar]]

For this curl request, the handler does not print the form values:

curl -H "Content-Type: application/json" -d '{"foo":"bar"}' http://localhost:3000
prints: map[]

Answer 1

ParseForm does not parse JSON request bodies. The output from the first example is unexpected.

Here's how to parse a JSON request body:

 func (s Server) ServeHTTP(w http.ResponseWriter, r *http.Request) {
    var v interface{}
    err := json.NewDecoder(r.Body).Decode(&v)
    if err != nil {
       // handle error
    }
    log.Println(v)
 }

You can define a type to match the structure of your JSON document and decode to that type:

 func (s Server) ServeHTTP(w http.ResponseWriter, r *http.Request) {
    var v struct {
       Foo string `json:"foo"`
    }
    err := json.NewDecoder(r.Body).Decode(&v)
    if err != nil {
       // handle error
    }
    log.Printf("%#v", v) // logs struct { Foo string "json:\"foo\"" }{Foo:"bar"} for your input
 }