Golang - Hello PATH HTTP Server Example

1_http_hello.go

package main

import (
  "fmt"
  "log"
  "net/http"
)

func Log(handler http.Handler) http.Handler {
  return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
    log.Printf("%s %s %s", r.RemoteAddr, r.Method, r.URL)
    handler.ServeHTTP(w, r)
  })
}

func handler(w http.ResponseWriter, r *http.Request) {
  fmt.Fprintf(w, "Hello %s!", r.URL.Path)
}

func main() {
  http.HandleFunc("/", handler)
  http.ListenAndServe(":8000", Log(http.DefaultServeMux))
}

2_http_advanced_example.go

package main

import (
  "fmt"
  "strings"
  "log"
  "net/http"
  "io/ioutil"
  "encoding/json"
)

func Log(handler http.Handler) http.Handler {
  return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
    log.Printf("%s %s %s", r.RemoteAddr, r.Method, r.URL)
    handler.ServeHTTP(w, r)
  })
}

func filename(name string) string {
  if name == "" {
    name = "query"
  }

  // A little security, but don't be fooled, this still isn't really safe.
  name = strings.Replace(name, ".", "", -1)
  name = strings.TrimPrefix(name, "/")
  name += ".txt"
  return name
}

func get(res http.ResponseWriter, req *http.Request) {
  // Example of fetching specific Query Param.
  name := filename(req.Form.Get("name"))
  body, err := ioutil.ReadFile(name)
  if err != nil {
    fmt.Fprintf(res, string(body[:]))
  } else {
    fmt.Fprintf(res, "Error: ", err)
  }
}

func post(res http.ResponseWriter, req *http.Request) {
  // Example of fetching specific Query Param.
  name := filename(req.Form.Get("name"))

  // Example of creating JSON string.
  body, err := json.Marshal(req.Form)
  if err != nil {
    fmt.Fprintf(res, "ERROR: ", err)
  } else {
    ioutil.WriteFile(name, body, 0600)
    fmt.Fprintf(res, string(body[:]))
  }
}

func bad(res http.ResponseWriter, req *http.Request) {
  fmt.Fprintf(res, "GO AWAY", req.Method, req.URL.Path)
}

func handler(res http.ResponseWriter, req *http.Request) {
  // Example of parsing GET or POST Query Params.
  req.ParseForm()

  // Example of handling POST request.
  switch req.Method {
  case "POST":
    post(res, req)
  // Example of handling GET request.
  case "GET":
    get(res, req)
  default:
    bad(res, req)
  }
}

func main() {
  fmt.Println("WARNING: This is an example, but not really safe.")
  http.HandleFunc("/", handler)
  http.ListenAndServe(":8000", Log(http.DefaultServeMux))
}