github.com/yukk001/go1.10.8@v0.0.0-20190813125351-6df2d3982e20/doc/articles/wiki/final-noclosure.go (about)

     1  // Copyright 2010 The Go Authors. All rights reserved.
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  
     5  package main
     6  
     7  import (
     8  	"errors"
     9  	"html/template"
    10  	"io/ioutil"
    11  	"log"
    12  	"net/http"
    13  	"regexp"
    14  )
    15  
    16  type Page struct {
    17  	Title string
    18  	Body  []byte
    19  }
    20  
    21  func (p *Page) save() error {
    22  	filename := p.Title + ".txt"
    23  	return ioutil.WriteFile(filename, p.Body, 0600)
    24  }
    25  
    26  func loadPage(title string) (*Page, error) {
    27  	filename := title + ".txt"
    28  	body, err := ioutil.ReadFile(filename)
    29  	if err != nil {
    30  		return nil, err
    31  	}
    32  	return &Page{Title: title, Body: body}, nil
    33  }
    34  
    35  func viewHandler(w http.ResponseWriter, r *http.Request) {
    36  	title, err := getTitle(w, r)
    37  	if err != nil {
    38  		return
    39  	}
    40  	p, err := loadPage(title)
    41  	if err != nil {
    42  		http.Redirect(w, r, "/edit/"+title, http.StatusFound)
    43  		return
    44  	}
    45  	renderTemplate(w, "view", p)
    46  }
    47  
    48  func editHandler(w http.ResponseWriter, r *http.Request) {
    49  	title, err := getTitle(w, r)
    50  	if err != nil {
    51  		return
    52  	}
    53  	p, err := loadPage(title)
    54  	if err != nil {
    55  		p = &Page{Title: title}
    56  	}
    57  	renderTemplate(w, "edit", p)
    58  }
    59  
    60  func saveHandler(w http.ResponseWriter, r *http.Request) {
    61  	title, err := getTitle(w, r)
    62  	if err != nil {
    63  		return
    64  	}
    65  	body := r.FormValue("body")
    66  	p := &Page{Title: title, Body: []byte(body)}
    67  	err = p.save()
    68  	if err != nil {
    69  		http.Error(w, err.Error(), http.StatusInternalServerError)
    70  		return
    71  	}
    72  	http.Redirect(w, r, "/view/"+title, http.StatusFound)
    73  }
    74  
    75  func renderTemplate(w http.ResponseWriter, tmpl string, p *Page) {
    76  	t, err := template.ParseFiles(tmpl + ".html")
    77  	if err != nil {
    78  		http.Error(w, err.Error(), http.StatusInternalServerError)
    79  		return
    80  	}
    81  	err = t.Execute(w, p)
    82  	if err != nil {
    83  		http.Error(w, err.Error(), http.StatusInternalServerError)
    84  	}
    85  }
    86  
    87  var validPath = regexp.MustCompile("^/(edit|save|view)/([a-zA-Z0-9]+)$")
    88  
    89  func getTitle(w http.ResponseWriter, r *http.Request) (string, error) {
    90  	m := validPath.FindStringSubmatch(r.URL.Path)
    91  	if m == nil {
    92  		http.NotFound(w, r)
    93  		return "", errors.New("Invalid Page Title")
    94  	}
    95  	return m[2], nil // The title is the second subexpression.
    96  }
    97  
    98  func main() {
    99  	http.HandleFunc("/view/", viewHandler)
   100  	http.HandleFunc("/edit/", editHandler)
   101  	http.HandleFunc("/save/", saveHandler)
   102  	log.Fatal(http.ListenAndServe(":8080", nil))
   103  }