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annotate controllers/json.go @ 257:dfc2b035e055

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Slimming down the signature of the JSONHandler type to not take the http.ResponseWriter. Idea of this handler is to simply transform JSON to JSON. The input is already parsed. The output is generated from JSONResult. So there is no need to pass the ResponseWriter to the handler function.
author Sascha L. Teichmann <sascha.teichmann@intevation.de>
date Fri, 27 Jul 2018 13:03:56 +0200
parents 3b688fe04c39
children 0777aa6de45b
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3771788d3dae Reduce boilerplate code when writing JSON parsing/generating endpoints.
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1 package controllers
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2
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3 import (
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4 "database/sql"
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5 "encoding/json"
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6 "fmt"
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7 "log"
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8 "net/http"
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9
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10 "github.com/jackc/pgx"
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11
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12 "gemma.intevation.de/gemma/auth"
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13 )
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14
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15 type JSONResult struct {
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16 Code int
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17 Result interface{}
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18 }
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19
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20 type JSONHandler struct {
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21 Input func() interface{}
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22 Handle func(interface{}, *http.Request, *sql.DB) (JSONResult, error)
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23 }
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24
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25 type JSONError struct {
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26 Code int
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27 Message string
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28 }
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29
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30 func (je JSONError) Error() string {
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31 return fmt.Sprintf("%d: %s", je.Code, je.Message)
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32 }
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33
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34 func (j *JSONHandler) ServeHTTP(rw http.ResponseWriter, req *http.Request) {
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35
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36 var input interface{}
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37 if j.Input != nil {
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38 input = j.Input()
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39 defer req.Body.Close()
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40 if err := json.NewDecoder(req.Body).Decode(input); err != nil {
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41 http.Error(rw, "error: "+err.Error(), http.StatusBadRequest)
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42 return
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43 }
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44 }
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46 token, _ := auth.GetToken(req)
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47 var jr JSONResult
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48 err := auth.ConnPool.Do(token, func(db *sql.DB) (err error) {
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49 jr, err = j.Handle(input, req, db)
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50 return err
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51 })
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52
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53 if err != nil {
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54 switch e := err.(type) {
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55 case pgx.PgError:
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56 var res = struct {
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57 Result string `json:"result"`
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58 Code string `json:"code"`
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59 Message string `json:"message"`
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60 }{
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61 Result: "failure",
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62 Code: e.Code,
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63 Message: e.Message,
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64 }
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65 rw.Header().Set("Content-Type", "application/json")
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66 rw.WriteHeader(http.StatusInternalServerError)
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67 if err := json.NewEncoder(rw).Encode(&res); err != nil {
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68 log.Printf("error: %v\n", err)
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69 }
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70 case JSONError:
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71 rw.Header().Set("Content-Type", "application/json")
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72 rw.WriteHeader(http.StatusInternalServerError)
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73 var res = struct {
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74 Message string `json:"message"`
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75 }{
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76 Message: e.Message,
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77 }
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78 if err := json.NewEncoder(rw).Encode(&res); err != nil {
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79 log.Printf("error: %v\n", err)
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80 }
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81 default:
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82 log.Printf("err: %v\n", err)
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83 http.Error(rw,
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84 "error: "+err.Error(),
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85 http.StatusInternalServerError)
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86 }
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87 return
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88 }
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89
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90 if jr.Code == 0 {
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91 jr.Code = http.StatusOK
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92 }
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93
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94 if jr.Code != http.StatusNoContent {
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95 rw.Header().Set("Content-Type", "application/json")
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96 }
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97 rw.WriteHeader(jr.Code)
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98 if jr.Code != http.StatusNoContent {
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99 if err := json.NewEncoder(rw).Encode(jr.Result); err != nil {
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100 log.Printf("error: %v\n", err)
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101 }
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102 }
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103 }