Templating

Web server wrapper

Based on the Effective Go web server example.

There is a service at chart.apis.google.com for formatting of charts and graphs, including a QR code. But it is tricky to use by URL. The program provides an interface to receive text, call the chart server and produce a QR code, which can be read by a cell phone camera.

Note chart type qr in the URL.

main.go

  package main

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

  const ADDRESS = ":8000"

  const TEMPLATE_STR = `
      <html>
      <head>
          <title>QR Link Generator</title>
      </head>

      <body>
          <h1>QR Link Generator</h1>

          {{if .}}
              <img src="http://chart.apis.google.com/chart?chs=300x300&cht=qr&choe=UTF-8&chl={{.}}" />
              <br>
              {{.}}
              <br>
              <br>
          {{end}}

          <form action="/" name=f method="GET">
              <input name="s" value="" title="Text to QR Encode" maxLength=1024 size=70 >

              <input type="submit" name="qr" value="Show QR" >
          </form>
      </body>
      </html>
  `

  var TEMPLATE = template.Must(template.New("qr").Parse(TEMPLATE_STR))

  func QR(w http.ResponseWriter, req *http.Request) {
      TEMPLATE.Execute(w, req.FormValue("s"))
  }

  func main() {
      http.Handle("/", http.HandlerFunc(QR))

      fmt.Printf("Starting server on http://localhost%v/\n", ADDRESS)

      err := http.ListenAndServe(ADDRESS, nil)
      if err != nil {
          log.Fatal("ListenAndServe:", err)
      }
  }

Run it:

$ go run main.go

Then open the browser at:

http://localhost:8000/

Start on a custom port:

go run main.go --addr :9000

In the form, enter an HTTP URL. You can enter “Hello world” but that can’t be found by a browser.

See the Image Charts documentation or the QR docs.

Sample URL:

https://chart.googleapis.com/chart?
  cht=p3&
  chs=250x100&
  chd=t:60,40&
  chl=Hello|World

https://chart.googleapis.com/chart?
    cht=qr
    chl=Hello+world
    choe=UTF-8

See the html/template docs for more info.