Go HTTP Server Handling http method, accessing query strings & request body
Example
Here are a simple example of some common tasks related to developing an API, differentiating between the HTTP Method of the request, accessing query string values and accessing the request body.
Resources
package main
import (
"fmt"
"io/ioutil"
"log"
"net/http"
)
type customHandler struct{}
// ServeHTTP implements the http.Handler interface in the net/http package
func (h customHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
// ParseForm will parse query string values and make r.Form available
r.ParseForm()
// r.Form is map of query string parameters
// its' type is url.Values, which in turn is a map[string][]string
queryMap := r.Form
switch r.Method {
case http.MethodGet:
// Handle GET requests
w.WriteHeader(http.StatusOK)
w.Write([]byte(fmt.Sprintf("Query string values: %s", queryMap)))
return
case http.MethodPost:
// Handle POST requests
body, err := ioutil.ReadAll(r.Body)
if err != nil {
// Error occurred while parsing request body
w.WriteHeader(http.StatusBadRequest)
return
}
w.WriteHeader(http.StatusOK)
w.Write([]byte(fmt.Sprintf("Query string values: %s\nBody posted: %s", queryMap, body)))
return
}
// Other HTTP methods (eg PUT, PATCH, etc) are not handled by the above
// so inform the client with appropriate status code
w.WriteHeader(http.StatusMethodNotAllowed)
}
func main() {
// All URLs will be handled by this function
// http.Handle, similarly to http.HandleFunc
// uses the DefaultServeMux
http.Handle("/", customHandler{})
// Continue to process new requests until an error occurs
log.Fatal(http.ListenAndServe(":8080", nil))
}
Sample curl output:
$ curl -i 'localhost:8080?city=Seattle&state=WA' -H 'Content-Type: text/plain' -X GET
HTTP/1.1 200 OK
Date: Fri, 02 Sep 2016 16:36:24 GMT
Content-Length: 51
Content-Type: text/plain; charset=utf-8
Query string values: map[city:[Seattle] state:[WA]]%
$ curl -i 'localhost:8080?city=Seattle&state=WA' -H 'Content-Type: text/plain' -X POST -d "some post data"
HTTP/1.1 200 OK
Date: Fri, 02 Sep 2016 16:36:35 GMT
Content-Length: 79
Content-Type: text/plain; charset=utf-8
Query string values: map[city:[Seattle] state:[WA]]
Body posted: some post data%
$ curl -i 'localhost:8080?city=Seattle&state=WA' -H 'Content-Type: text/plain' -X PUT
HTTP/1.1 405 Method Not Allowed
Date: Fri, 02 Sep 2016 16:36:41 GMT
Content-Length: 0
Content-Type: text/plain; charset=utf-8
