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comparison controllers/json.go @ 237:3771788d3dae

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Reduce boilerplate code when writing JSON parsing/generating endpoints.
author Sascha L. Teichmann <sascha.teichmann@intevation.de>
date Thu, 26 Jul 2018 17:07:03 +0200
parents
children 2b39bf2bf1fd
comparison
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236:664fe6536141 237:3771788d3dae
1 package controllers
2
3 import (
4 "database/sql"
5 "encoding/json"
6 "fmt"
7 "log"
8 "net/http"
9
10 "gemma.intevation.de/gemma/auth"
11 "github.com/jackc/pgx"
12 )
13
14 type JSONResult struct {
15 Code int
16 Result interface{}
17 }
18
19 type JSONHandler struct {
20 Input func() interface{}
21 Process func(http.ResponseWriter, *http.Request, interface{}, *sql.DB) (JSONResult, error)
22 }
23
24 type JSONError struct {
25 Code int
26 Message string
27 }
28
29 func (je JSONError) Error() string {
30 return fmt.Sprintf("%d: %s", je.Code, je.Message)
31 }
32
33 func (j *JSONHandler) ServeHTTP(rw http.ResponseWriter, req *http.Request) {
34
35 var input interface{}
36 if j.Input != nil {
37 input = j.Input()
38 defer req.Body.Close()
39 if err := json.NewDecoder(req.Body).Decode(input); err != nil {
40 http.Error(rw, "error: "+err.Error(), http.StatusBadRequest)
41 return
42 }
43 }
44
45 token, _ := auth.GetToken(req)
46 var jr JSONResult
47 err := auth.ConnPool.Do(token, func(db *sql.DB) (err error) {
48 jr, err = j.Process(rw, req, input, db)
49 return err
50 })
51
52 if err != nil {
53 switch e := err.(type) {
54 case pgx.PgError:
55 var res = struct {
56 Result string `json:"result"`
57 Code string `json:"code,omitempty"`
58 Message string `json:"message,omitempty"`
59 }{
60 Result: "failure",
61 Code: e.Code,
62 Message: e.Message,
63 }
64 rw.Header().Set("Content-Type", "application/json")
65 rw.WriteHeader(http.StatusInternalServerError)
66 if err := json.NewEncoder(rw).Encode(&res); err != nil {
67 log.Printf("error: %v\n", err)
68 }
69 case JSONError:
70 rw.Header().Set("Content-Type", "application/json")
71 rw.WriteHeader(http.StatusInternalServerError)
72 var res = struct {
73 Message string `json:"message"`
74 }{
75 Message: e.Message,
76 }
77 if err := json.NewEncoder(rw).Encode(&res); err != nil {
78 log.Printf("error: %v\n", err)
79 }
80 default:
81 log.Printf("err: %v\n", err)
82 http.Error(rw,
83 "error: "+err.Error(),
84 http.StatusInternalServerError)
85 }
86 return
87 }
88
89 rw.Header().Set("Content-Type", "application/json")
90 rw.WriteHeader(jr.Code)
91 if err := json.NewEncoder(rw).Encode(jr.Result); err != nil {
92 log.Printf("error: %v\n", err)
93 }
94 }