1 // Copyright 2011 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 // This file contains the code snippets included in "Error Handling and Go." 6 7 package main 8 9 import ( 10 "net/http" 11 "text/template" 12 ) 13 14 type appError struct { 15 Error error 16 Message string 17 Code int 18 } 19 20 // STOP OMIT 21 22 type appHandler func(http.ResponseWriter, *http.Request) *appError 23 24 func (fn appHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) { 25 if e := fn(w, r); e != nil { // e is *appError, not error. 26 c := appengine.NewContext(r) 27 c.Errorf("%v", e.Error) 28 http.Error(w, e.Message, e.Code) 29 } 30 } 31 32 // STOP OMIT 33 34 func viewRecord(w http.ResponseWriter, r *http.Request) *appError { 35 c := appengine.NewContext(r) 36 key := datastore.NewKey(c, "Record", r.FormValue("id"), 0, nil) 37 record := new(Record) 38 if err := datastore.Get(c, key, record); err != nil { 39 return &appError{err, "Record not found", 404} 40 } 41 if err := viewTemplate.Execute(w, record); err != nil { 42 return &appError{err, "Can't display record", 500} 43 } 44 return nil 45 } 46 47 // STOP OMIT 48 49 func init() { 50 http.Handle("/view", appHandler(viewRecord)) 51 } 52 53 type ap struct{} 54 55 func (ap) NewContext(*http.Request) *ctx { return nil } 56 57 type ctx struct{} 58 59 func (*ctx) Errorf(string, ...interface{}) {} 60 61 var appengine ap 62 63 type ds struct{} 64 65 func (ds) NewKey(*ctx, string, string, int, *int) string { return "" } 66 func (ds) Get(*ctx, string, *Record) error { return nil } 67 68 var datastore ds 69 70 type Record struct{} 71 72 var viewTemplate *template.Template 73 74 func main() {} 75
