beginner-webdev-journey

Step 4: Web routing handling edit/view dari txt file

  1. Buat file step4.go dengan isi berikut
// Copyright 2010 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

//go:build ignore

package main

import (
	"html/template"
	"log"
	"net/http"
	"os"
	"regexp"
)

type Page struct {
	Title string
	Body  []byte
}

func (p *Page) save() error {
	filename := p.Title + ".txt"
	return os.WriteFile(filename, p.Body, 0600)
}

func loadPage(title string) (*Page, error) {
	filename := title + ".txt"
	body, err := os.ReadFile(filename)
	if err != nil {
		return nil, err
	}
	return &Page{Title: title, Body: body}, nil
}

func viewHandler(w http.ResponseWriter, r *http.Request, title string) {
	p, err := loadPage(title)
	if err != nil {
		http.Redirect(w, r, "/edit/"+title, http.StatusFound)
		return
	}
	renderTemplate(w, "view", p)
}

func editHandler(w http.ResponseWriter, r *http.Request, title string) {
	p, err := loadPage(title)
	if err != nil {
		p = &Page{Title: title}
	}
	renderTemplate(w, "edit", p)
}

func saveHandler(w http.ResponseWriter, r *http.Request, title string) {
	body := r.FormValue("body")
	p := &Page{Title: title, Body: []byte(body)}
	err := p.save()
	if err != nil {
		http.Error(w, err.Error(), http.StatusInternalServerError)
		return
	}
	http.Redirect(w, r, "/view/"+title, http.StatusFound)
}

var templates = template.Must(template.ParseFiles("edit.html", "view.html"))

func renderTemplate(w http.ResponseWriter, tmpl string, p *Page) {
	err := templates.ExecuteTemplate(w, tmpl+".html", p)
	if err != nil {
		http.Error(w, err.Error(), http.StatusInternalServerError)
	}
}

var validPath = regexp.MustCompile("^/(edit|save|view)/([a-zA-Z0-9]+)$")

func makeHandler(fn func(http.ResponseWriter, *http.Request, string)) http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		m := validPath.FindStringSubmatch(r.URL.Path)
		if m == nil {
			http.NotFound(w, r)
			return
		}
		fn(w, r, m[2])
	}
}

func main() {
	http.HandleFunc("/view/", makeHandler(viewHandler))
	http.HandleFunc("/edit/", makeHandler(editHandler))
	http.HandleFunc("/save/", makeHandler(saveHandler))

	log.Fatal(http.ListenAndServe(":8080", nil))
}
  1. Buat file view.html pada folder yang sama dengan step4.go, isi dengan file berikut
<!DOCTYPE html>
<html>
<head>
    <title></title>
</head>
<body>

<h1></h1>

<div>
    <pre></pre>
</div>

<p>
    <a href="/edit/">Edit this page</a>
</p>

</body>
</html>
  1. Buat file edit.html pada folder yang sama dengan step4.go, isi dengan file berikut
<!DOCTYPE html>
<html>
<head>
    <title>Edit </title>
</head>
<body>

<h1>Editing </h1>

<form action="/save/" method="POST">
    <div>
        <textarea name="body" rows="20" cols="80"></textarea>
    </div>
    <div>
        <input type="submit" value="Save">
    </div>
</form>

<p>
    <a href="/view/">Back to view</a>
</p>

</body>
</html>

  1. Buat file test.txt pada folder yang sama dengan step4.go, isi bebas

  2. Compile and run step4.go

go build step4.go

step4

Atau langsung compile dan run

go run step4.go

  1. Perhantikan hasil pada url http://localhost:8080/view/test

  2. Coba apabila ke url yang file txt yang belum ada http://localhost:8080/edit/belumadafile

  3. Perhatikan apa yang terjadi.

Ini adalah suatu proses routing handling, ketika ke url yang belum ada suatu file-nya, maka path akan pindah ke path localhost/edit, dan bisa membuat file txt baru disana. Sedangkan ketika file txt sudah ada maka bisa mengakses url seperti localhost/view/test bisa mengakses endpoint test karena sudah ada file test.txt

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