1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
|
<!DOCTYPE html>
<html lang="en">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<meta name="description" content="Home for a73x" />
<meta name="author" content="a73x" />
<meta name="viewport"
content="user-scalable=no, initial-scale=1.0, maximum-scale=1.0, minimum-scale=1.0, width=device-width" />
<title>a73x</title>
<link rel="stylesheet" href="/static/styles.css">
<link rel="stylesheet" href="/static/syntax.css">
<link rel="icon" type="image/x-icon" href="/static/favicon.svg">
</head>
<body>
<main>
<div class="header">
<div class="header-title">
<h1>a73x</h1>
<sub>high effort, low reward</sub>
</div>
<nav class="nav">
<ul>
<li><a class="no-decorations" href="/">home</a></li>
<li><a class="no-decorations" href="/posts">posts</a></li>
<li><a class="no-decorations" href="/ethos">ethos</a></li>
</ul>
</nav>
</div>
<a href="/posts">← Posts</a>
<h1>Writing HTTP Handlers</h1>
<p>I’m sharing how I write handlers in Go.</p>
<p>I write them like this for reasons that are probably fairly contextual. I’ve written a few applications and had to swap REST libraries or even swapped REST for GRPC, so things that make that easier speak to me a great deal.</p>
<p>I’ve used <code>ints</code> instead of the <code>http.StatusXXXX</code> and omitted <code>JSON</code> tags in an attempt to try save up screen space.</p>
<p>To begin with, you might have something like this:</p>
<pre tabindex="0" class="chroma"><code><span class="line"><span class="cl"><span class="kn">package</span> <span class="nx">main</span>
</span></span><span class="line"><span class="cl">
</span></span><span class="line"><span class="cl"><span class="kn">import</span> <span class="p">(</span>
</span></span><span class="line"><span class="cl"> <span class="s">"fmt"</span>
</span></span><span class="line"><span class="cl"> <span class="s">"log"</span>
</span></span><span class="line"><span class="cl"> <span class="s">"net/http"</span>
</span></span><span class="line"><span class="cl"><span class="p">)</span>
</span></span><span class="line"><span class="cl">
</span></span><span class="line"><span class="cl"><span class="kd">func</span> <span class="nf">handler</span><span class="p">(</span><span class="nx">w</span> <span class="nx">http</span><span class="p">.</span><span class="nx">ResponseWriter</span><span class="p">,</span> <span class="nx">r</span> <span class="o">*</span><span class="nx">http</span><span class="p">.</span><span class="nx">Request</span><span class="p">)</span> <span class="p">{</span>
</span></span><span class="line"><span class="cl"> <span class="nx">fmt</span><span class="p">.</span><span class="nf">Fprintf</span><span class="p">(</span><span class="nx">w</span><span class="p">,</span> <span class="s">"Hello, World!"</span><span class="p">)</span>
</span></span><span class="line"><span class="cl"><span class="p">}</span>
</span></span><span class="line"><span class="cl">
</span></span><span class="line"><span class="cl"><span class="kd">func</span> <span class="nf">main</span><span class="p">()</span> <span class="p">{</span>
</span></span><span class="line"><span class="cl"> <span class="nx">http</span><span class="p">.</span><span class="nf">HandleFunc</span><span class="p">(</span><span class="s">"/"</span><span class="p">,</span> <span class="nx">handler</span><span class="p">)</span>
</span></span><span class="line"><span class="cl"> <span class="nx">log</span><span class="p">.</span><span class="nf">Fatal</span><span class="p">(</span><span class="nx">http</span><span class="p">.</span><span class="nf">ListenAndServe</span><span class="p">(</span><span class="s">":8080"</span><span class="p">,</span> <span class="kc">nil</span><span class="p">))</span>
</span></span><span class="line"><span class="cl"><span class="p">}</span>
</span></span><span class="line"><span class="cl">
</span></span></code></pre>
<p>Then you might get told off because you’ve just registered routes with the default mux, which isn’t very testable.</p>
<p>So you tweak it a little bit.</p>
<pre tabindex="0" class="chroma"><code><span class="line"><span class="cl"><span class="kn">package</span> <span class="nx">main</span>
</span></span><span class="line"><span class="cl">
</span></span><span class="line"><span class="cl"><span class="kn">import</span> <span class="p">(</span>
</span></span><span class="line"><span class="cl"> <span class="s">"fmt"</span>
</span></span><span class="line"><span class="cl"> <span class="s">"log"</span>
</span></span><span class="line"><span class="cl"> <span class="s">"net/http"</span>
</span></span><span class="line"><span class="cl"><span class="p">)</span>
</span></span><span class="line"><span class="cl">
</span></span><span class="line"><span class="cl"><span class="kd">func</span> <span class="nf">handler</span><span class="p">(</span><span class="nx">w</span> <span class="nx">http</span><span class="p">.</span><span class="nx">ResponseWriter</span><span class="p">,</span> <span class="nx">r</span> <span class="o">*</span><span class="nx">http</span><span class="p">.</span><span class="nx">Request</span><span class="p">)</span> <span class="p">{</span>
</span></span><span class="line"><span class="cl"> <span class="nx">fmt</span><span class="p">.</span><span class="nf">Fprintf</span><span class="p">(</span><span class="nx">w</span><span class="p">,</span> <span class="s">"Hello, World!"</span><span class="p">)</span>
</span></span><span class="line"><span class="cl"><span class="p">}</span>
</span></span><span class="line"><span class="cl">
</span></span><span class="line"><span class="cl"><span class="kd">func</span> <span class="nf">newMux</span><span class="p">()</span> <span class="o">*</span><span class="nx">http</span><span class="p">.</span><span class="nx">ServeMux</span> <span class="p">{</span>
</span></span><span class="line"><span class="cl"> <span class="nx">mux</span> <span class="o">:=</span> <span class="nx">http</span><span class="p">.</span><span class="nf">NewServeMux</span><span class="p">()</span>
</span></span><span class="line"><span class="cl"> <span class="nx">mux</span><span class="p">.</span><span class="nf">HandleFunc</span><span class="p">(</span><span class="s">"/"</span><span class="p">,</span> <span class="nx">handler</span><span class="p">)</span>
</span></span><span class="line"><span class="cl">
</span></span><span class="line"><span class="cl"> <span class="k">return</span> <span class="nx">mux</span>
</span></span><span class="line"><span class="cl"><span class="p">}</span>
</span></span><span class="line"><span class="cl">
</span></span><span class="line"><span class="cl"><span class="kd">func</span> <span class="nf">Run</span><span class="p">()</span> <span class="kt">error</span> <span class="p">{</span>
</span></span><span class="line"><span class="cl"> <span class="nx">mux</span> <span class="o">:=</span> <span class="nf">newMux</span><span class="p">()</span>
</span></span><span class="line"><span class="cl"> <span class="k">return</span> <span class="nx">http</span><span class="p">.</span><span class="nf">ListenAndServe</span><span class="p">(</span><span class="s">":8080"</span><span class="p">,</span> <span class="nx">mux</span><span class="p">)</span>
</span></span><span class="line"><span class="cl"><span class="p">}</span>
</span></span><span class="line"><span class="cl">
</span></span><span class="line"><span class="cl"><span class="kd">func</span> <span class="nf">main</span><span class="p">()</span> <span class="p">{</span>
</span></span><span class="line"><span class="cl"> <span class="k">if</span> <span class="nx">err</span> <span class="o">:=</span> <span class="nf">Run</span><span class="p">();</span> <span class="nx">err</span> <span class="o">!=</span> <span class="kc">nil</span> <span class="p">{</span>
</span></span><span class="line"><span class="cl"> <span class="nx">log</span><span class="p">.</span><span class="nf">Fatal</span><span class="p">(</span><span class="nx">err</span><span class="p">)</span>
</span></span><span class="line"><span class="cl"> <span class="p">}</span>
</span></span><span class="line"><span class="cl"><span class="p">}</span>
</span></span></code></pre>
<p><code>newMux()</code> gives you a <code>mux</code> to use when testing.</p>
<p><code>Run</code> keeps <code>main</code> nice and clean, so you can just return errors as needed instead of going <code>log.Fatal</code> and just generally being messy.</p>
<p>But now you need to do something real, you want to store and fetch data.</p>
<pre tabindex="0" class="chroma"><code><span class="line"><span class="cl"><span class="kn">package</span> <span class="nx">main</span>
</span></span><span class="line"><span class="cl">
</span></span><span class="line"><span class="cl"><span class="kn">import</span> <span class="p">(</span>
</span></span><span class="line"><span class="cl"> <span class="s">"encoding/json"</span>
</span></span><span class="line"><span class="cl"> <span class="s">"fmt"</span>
</span></span><span class="line"><span class="cl"> <span class="s">"log"</span>
</span></span><span class="line"><span class="cl"> <span class="s">"net/http"</span>
</span></span><span class="line"><span class="cl"> <span class="s">"strconv"</span>
</span></span><span class="line"><span class="cl"><span class="p">)</span>
</span></span><span class="line"><span class="cl">
</span></span><span class="line"><span class="cl"><span class="kd">func</span> <span class="nf">NewMux</span><span class="p">()</span> <span class="o">*</span><span class="nx">http</span><span class="p">.</span><span class="nx">ServeMux</span> <span class="p">{</span>
</span></span><span class="line"><span class="cl"> <span class="nx">mux</span> <span class="o">:=</span> <span class="nx">http</span><span class="p">.</span><span class="nf">NewServeMux</span><span class="p">()</span>
</span></span><span class="line"><span class="cl"> <span class="nx">s</span> <span class="o">:=</span> <span class="nx">Server</span><span class="p">{</span>
</span></span><span class="line"><span class="cl"> <span class="nx">data</span><span class="p">:</span> <span class="nb">make</span><span class="p">(</span><span class="kd">map</span><span class="p">[</span><span class="kt">int</span><span class="p">]</span><span class="nx">Content</span><span class="p">),</span>
</span></span><span class="line"><span class="cl"> <span class="p">}</span>
</span></span><span class="line"><span class="cl">
</span></span><span class="line"><span class="cl"> <span class="nx">s</span><span class="p">.</span><span class="nf">Register</span><span class="p">(</span><span class="nx">mux</span><span class="p">)</span>
</span></span><span class="line"><span class="cl"> <span class="k">return</span> <span class="nx">mux</span>
</span></span><span class="line"><span class="cl"><span class="p">}</span>
</span></span><span class="line"><span class="cl">
</span></span><span class="line"><span class="cl"><span class="kd">func</span> <span class="nf">Run</span><span class="p">()</span> <span class="kt">error</span> <span class="p">{</span>
</span></span><span class="line"><span class="cl"> <span class="nx">mux</span> <span class="o">:=</span> <span class="nf">NewMux</span><span class="p">()</span>
</span></span><span class="line"><span class="cl"> <span class="k">return</span> <span class="nx">http</span><span class="p">.</span><span class="nf">ListenAndServe</span><span class="p">(</span><span class="s">":8080"</span><span class="p">,</span> <span class="nx">mux</span><span class="p">)</span>
</span></span><span class="line"><span class="cl"><span class="p">}</span>
</span></span><span class="line"><span class="cl">
</span></span><span class="line"><span class="cl"><span class="kd">type</span> <span class="nx">Server</span> <span class="kd">struct</span> <span class="p">{</span>
</span></span><span class="line"><span class="cl"> <span class="nx">data</span> <span class="kd">map</span><span class="p">[</span><span class="kt">int</span><span class="p">]</span><span class="nx">Content</span>
</span></span><span class="line"><span class="cl"><span class="p">}</span>
</span></span><span class="line"><span class="cl">
</span></span><span class="line"><span class="cl"><span class="kd">func</span> <span class="p">(</span><span class="nx">s</span> <span class="o">*</span><span class="nx">Server</span><span class="p">)</span> <span class="nf">Register</span><span class="p">(</span><span class="nx">mux</span> <span class="o">*</span><span class="nx">http</span><span class="p">.</span><span class="nx">ServeMux</span><span class="p">)</span> <span class="p">{</span>
</span></span><span class="line"><span class="cl"> <span class="nx">mux</span><span class="p">.</span><span class="nf">HandleFunc</span><span class="p">(</span><span class="s">"GET /{id}"</span><span class="p">,</span> <span class="nx">s</span><span class="p">.</span><span class="nx">Get</span><span class="p">)</span>
</span></span><span class="line"><span class="cl"> <span class="nx">mux</span><span class="p">.</span><span class="nf">HandleFunc</span><span class="p">(</span><span class="s">"POST /"</span><span class="p">,</span> <span class="nx">s</span><span class="p">.</span><span class="nx">Post</span><span class="p">)</span>
</span></span><span class="line"><span class="cl"><span class="p">}</span>
</span></span><span class="line"><span class="cl">
</span></span><span class="line"><span class="cl"><span class="kd">func</span> <span class="p">(</span><span class="nx">s</span> <span class="o">*</span><span class="nx">Server</span><span class="p">)</span> <span class="nf">Get</span><span class="p">(</span><span class="nx">w</span> <span class="nx">http</span><span class="p">.</span><span class="nx">ResponseWriter</span><span class="p">,</span> <span class="nx">r</span> <span class="o">*</span><span class="nx">http</span><span class="p">.</span><span class="nx">Request</span><span class="p">)</span> <span class="p">{</span>
</span></span><span class="line"><span class="cl"> <span class="nx">idStr</span> <span class="o">:=</span> <span class="nx">r</span><span class="p">.</span><span class="nf">PathValue</span><span class="p">(</span><span class="s">"id"</span><span class="p">)</span>
</span></span><span class="line"><span class="cl"> <span class="nx">id</span><span class="p">,</span> <span class="nx">err</span> <span class="o">:=</span> <span class="nx">strconv</span><span class="p">.</span><span class="nf">Atoi</span><span class="p">(</span><span class="nx">idStr</span><span class="p">)</span>
</span></span><span class="line"><span class="cl"> <span class="k">if</span> <span class="nx">err</span> <span class="o">!=</span> <span class="kc">nil</span> <span class="p">{</span>
</span></span><span class="line"><span class="cl"> <span class="nx">w</span><span class="p">.</span><span class="nf">WriteHeader</span><span class="p">(</span><span class="mi">400</span><span class="p">)</span>
</span></span><span class="line"><span class="cl"> <span class="nx">w</span><span class="p">.</span><span class="nf">Write</span><span class="p">([]</span><span class="nb">byte</span><span class="p">(</span><span class="nx">fmt</span><span class="p">.</span><span class="nf">Sprintf</span><span class="p">(</span><span class="s">"failed to parse id: %v"</span><span class="p">,</span> <span class="nx">err</span><span class="p">)))</span>
</span></span><span class="line"><span class="cl"> <span class="k">return</span>
</span></span><span class="line"><span class="cl"> <span class="p">}</span>
</span></span><span class="line"><span class="cl"> <span class="nx">data</span><span class="p">,</span> <span class="nx">ok</span> <span class="o">:=</span> <span class="nx">s</span><span class="p">.</span><span class="nx">data</span><span class="p">[</span><span class="nx">id</span><span class="p">]</span>
</span></span><span class="line"><span class="cl"> <span class="k">if</span> <span class="p">!</span><span class="nx">ok</span> <span class="p">{</span>
</span></span><span class="line"><span class="cl"> <span class="nx">w</span><span class="p">.</span><span class="nf">WriteHeader</span><span class="p">(</span><span class="mi">404</span><span class="p">)</span>
</span></span><span class="line"><span class="cl"> <span class="nx">w</span><span class="p">.</span><span class="nf">Write</span><span class="p">([]</span><span class="nb">byte</span><span class="p">(</span><span class="s">"not found"</span><span class="p">))</span>
</span></span><span class="line"><span class="cl"> <span class="k">return</span>
</span></span><span class="line"><span class="cl"> <span class="p">}</span>
</span></span><span class="line"><span class="cl"> <span class="nx">w</span><span class="p">.</span><span class="nf">Header</span><span class="p">().</span><span class="nf">Set</span><span class="p">(</span><span class="s">"Content-Type"</span><span class="p">,</span> <span class="s">"application/json"</span><span class="p">)</span>
</span></span><span class="line"><span class="cl"> <span class="nx">w</span><span class="p">.</span><span class="nf">WriteHeader</span><span class="p">(</span><span class="mi">200</span><span class="p">)</span>
</span></span><span class="line"><span class="cl"> <span class="nx">json</span><span class="p">.</span><span class="nf">NewEncoder</span><span class="p">(</span><span class="nx">w</span><span class="p">).</span><span class="nf">Encode</span><span class="p">(</span><span class="nx">data</span><span class="p">)</span>
</span></span><span class="line"><span class="cl"><span class="p">}</span>
</span></span><span class="line"><span class="cl">
</span></span><span class="line"><span class="cl"><span class="kd">type</span> <span class="nx">ContentPostReq</span> <span class="kd">struct</span> <span class="p">{</span>
</span></span><span class="line"><span class="cl"> <span class="nx">Foo</span> <span class="kt">string</span>
</span></span><span class="line"><span class="cl"><span class="p">}</span>
</span></span><span class="line"><span class="cl">
</span></span><span class="line"><span class="cl"><span class="kd">func</span> <span class="p">(</span><span class="nx">s</span> <span class="o">*</span><span class="nx">Server</span><span class="p">)</span> <span class="nf">Post</span><span class="p">(</span><span class="nx">w</span> <span class="nx">http</span><span class="p">.</span><span class="nx">ResponseWriter</span><span class="p">,</span> <span class="nx">r</span> <span class="o">*</span><span class="nx">http</span><span class="p">.</span><span class="nx">Request</span><span class="p">)</span> <span class="p">{</span>
</span></span><span class="line"><span class="cl"> <span class="nx">req</span> <span class="o">:=</span> <span class="nx">ContentPostReq</span><span class="p">{}</span>
</span></span><span class="line"><span class="cl"> <span class="k">if</span> <span class="nx">err</span> <span class="o">:=</span> <span class="nx">json</span><span class="p">.</span><span class="nf">NewDecoder</span><span class="p">(</span><span class="nx">r</span><span class="p">.</span><span class="nx">Body</span><span class="p">).</span><span class="nf">Decode</span><span class="p">(</span><span class="o">&</span><span class="nx">req</span><span class="p">);</span> <span class="nx">err</span> <span class="o">!=</span> <span class="kc">nil</span> <span class="p">{</span>
</span></span><span class="line"><span class="cl"> <span class="nx">w</span><span class="p">.</span><span class="nf">WriteHeader</span><span class="p">(</span><span class="mi">400</span><span class="p">)</span>
</span></span><span class="line"><span class="cl"> <span class="nx">w</span><span class="p">.</span><span class="nf">Write</span><span class="p">([]</span><span class="nb">byte</span><span class="p">(</span><span class="nx">fmt</span><span class="p">.</span><span class="nf">Sprintf</span><span class="p">(</span><span class="s">"failed to parse request: %v"</span><span class="p">,</span> <span class="nx">err</span><span class="p">)))</span>
</span></span><span class="line"><span class="cl"> <span class="k">return</span>
</span></span><span class="line"><span class="cl"> <span class="p">}</span>
</span></span><span class="line"><span class="cl"> <span class="nx">id</span> <span class="o">:=</span> <span class="nb">len</span><span class="p">(</span><span class="nx">s</span><span class="p">.</span><span class="nx">data</span><span class="p">)</span>
</span></span><span class="line"><span class="cl"> <span class="nx">content</span> <span class="o">:=</span> <span class="nx">Content</span><span class="p">{</span>
</span></span><span class="line"><span class="cl"> <span class="nx">ID</span><span class="p">:</span> <span class="nx">id</span><span class="p">,</span>
</span></span><span class="line"><span class="cl"> <span class="nx">Foo</span><span class="p">:</span> <span class="nx">req</span><span class="p">.</span><span class="nx">Foo</span><span class="p">,</span>
</span></span><span class="line"><span class="cl"> <span class="p">}</span>
</span></span><span class="line"><span class="cl"> <span class="nx">s</span><span class="p">.</span><span class="nx">data</span><span class="p">[</span><span class="nx">id</span><span class="p">]</span> <span class="p">=</span> <span class="nx">content</span>
</span></span><span class="line"><span class="cl">
</span></span><span class="line"><span class="cl"> <span class="nx">w</span><span class="p">.</span><span class="nf">WriteHeader</span><span class="p">(</span><span class="mi">200</span><span class="p">)</span>
</span></span><span class="line"><span class="cl"> <span class="nx">json</span><span class="p">.</span><span class="nf">NewEncoder</span><span class="p">(</span><span class="nx">w</span><span class="p">).</span><span class="nf">Encode</span><span class="p">(</span><span class="nx">content</span><span class="p">)</span>
</span></span><span class="line"><span class="cl"><span class="p">}</span>
</span></span><span class="line"><span class="cl">
</span></span><span class="line"><span class="cl"><span class="kd">type</span> <span class="nx">Content</span> <span class="kd">struct</span> <span class="p">{</span>
</span></span><span class="line"><span class="cl"> <span class="nx">ID</span> <span class="kt">int</span>
</span></span><span class="line"><span class="cl"> <span class="nx">Foo</span> <span class="kt">string</span>
</span></span><span class="line"><span class="cl"><span class="p">}</span>
</span></span><span class="line"><span class="cl">
</span></span><span class="line"><span class="cl"><span class="kd">func</span> <span class="nf">main</span><span class="p">()</span> <span class="p">{</span>
</span></span><span class="line"><span class="cl"> <span class="k">if</span> <span class="nx">err</span> <span class="o">:=</span> <span class="nf">Run</span><span class="p">();</span> <span class="nx">err</span> <span class="o">!=</span> <span class="kc">nil</span> <span class="p">{</span>
</span></span><span class="line"><span class="cl"> <span class="nx">log</span><span class="p">.</span><span class="nf">Fatal</span><span class="p">(</span><span class="nx">err</span><span class="p">)</span>
</span></span><span class="line"><span class="cl"> <span class="p">}</span>
</span></span><span class="line"><span class="cl"><span class="p">}</span>
</span></span></code></pre><pre tabindex="0" class="chroma"><code><span class="line"><span class="cl">❯ curl -X POST localhost:8080 --header <span class="s2">"Content-Type: application/json"</span> -d <span class="s1">'{"foo":"bar"}'</span>
</span></span><span class="line"><span class="cl"><span class="o">{</span><span class="s2">"ID"</span>:0,<span class="s2">"Foo"</span>:<span class="s2">"bar"</span><span class="o">}</span>
</span></span><span class="line"><span class="cl">❯ curl -X GET localhost:8080/0
</span></span><span class="line"><span class="cl"><span class="o">{</span><span class="s2">"ID"</span>:0,<span class="s2">"Foo"</span>:<span class="s2">"bar"</span><span class="o">}</span>
</span></span></code></pre>
<p>Erm, well, okay. Quite a bit has changed here, but I’m sure you can read it. We now save and fetch very, very safely from a map and return the response as <code>JSON</code>. I’ve done some things for brevity because I want to get to the main point.</p>
<p>This API is inconsistent. It sometimes returns <code>JSON</code>, and the others return strings. Overall, it’s just a mess.</p>
<p>So let’s try to standardise things.
First, let’s design some form of REST spec.</p>
<pre tabindex="0" class="chroma"><code><span class="line"><span class="cl"><span class="kd">type</span> <span class="nx">JSONResp</span><span class="p">[</span><span class="nx">T</span> <span class="nx">any</span><span class="p">]</span> <span class="kd">struct</span> <span class="p">{</span>
</span></span><span class="line"><span class="cl"> <span class="nx">Resources</span> <span class="p">[]</span><span class="nx">T</span>
</span></span><span class="line"><span class="cl"> <span class="nx">Errs</span> <span class="p">[]</span><span class="nx">ErrorResp</span>
</span></span><span class="line"><span class="cl"><span class="p">}</span>
</span></span><span class="line"><span class="cl">
</span></span><span class="line"><span class="cl"><span class="kd">type</span> <span class="nx">ErrorResp</span> <span class="kd">struct</span> <span class="p">{</span>
</span></span><span class="line"><span class="cl"> <span class="nx">Status</span> <span class="kt">int</span>
</span></span><span class="line"><span class="cl"> <span class="nx">Msg</span> <span class="kt">string</span>
</span></span><span class="line"><span class="cl"><span class="p">}</span>
</span></span></code></pre>
<p>We want to be able to support fetching multiple resources at once, if we can only fetch some resources, let’s return them under <code>resources</code> and show the errors under <code>errs</code></p>
<p>Now, add some helpful functions to handle things.</p>
<pre tabindex="0" class="chroma"><code><span class="line"><span class="cl"><span class="kd">func</span> <span class="nx">Post</span><span class="p">[</span><span class="nx">In</span> <span class="nx">any</span><span class="p">,</span> <span class="nx">Out</span> <span class="nx">any</span><span class="p">](</span><span class="nx">successCode</span> <span class="kt">int</span><span class="p">,</span> <span class="nx">fn</span> <span class="kd">func</span><span class="p">(</span><span class="nx">context</span><span class="p">.</span><span class="nx">Context</span><span class="p">,</span> <span class="nx">In</span><span class="p">)</span> <span class="p">([]</span><span class="nx">Out</span><span class="p">,</span> <span class="p">[]</span><span class="nx">ErrorResp</span><span class="p">))</span> <span class="kd">func</span><span class="p">(</span><span class="nx">http</span><span class="p">.</span><span class="nx">ResponseWriter</span><span class="p">,</span> <span class="o">*</span><span class="nx">http</span><span class="p">.</span><span class="nx">Request</span><span class="p">)</span> <span class="p">{</span>
</span></span><span class="line"><span class="cl"> <span class="k">return</span> <span class="kd">func</span><span class="p">(</span><span class="nx">w</span> <span class="nx">http</span><span class="p">.</span><span class="nx">ResponseWriter</span><span class="p">,</span> <span class="nx">r</span> <span class="o">*</span><span class="nx">http</span><span class="p">.</span><span class="nx">Request</span><span class="p">)</span> <span class="p">{</span>
</span></span><span class="line"><span class="cl"> <span class="kd">var</span> <span class="nx">v</span> <span class="nx">In</span>
</span></span><span class="line"><span class="cl">
</span></span><span class="line"><span class="cl"> <span class="k">if</span> <span class="nx">err</span> <span class="o">:=</span> <span class="nx">json</span><span class="p">.</span><span class="nf">NewDecoder</span><span class="p">(</span><span class="nx">r</span><span class="p">.</span><span class="nx">Body</span><span class="p">).</span><span class="nf">Decode</span><span class="p">(</span><span class="o">&</span><span class="nx">v</span><span class="p">);</span> <span class="nx">err</span> <span class="o">!=</span> <span class="kc">nil</span> <span class="p">{</span>
</span></span><span class="line"><span class="cl"> <span class="nx">writeJSONResp</span><span class="p">[</span><span class="nx">Out</span><span class="p">](</span><span class="nx">w</span><span class="p">,</span> <span class="nx">http</span><span class="p">.</span><span class="nx">StatusBadRequest</span><span class="p">,</span> <span class="kc">nil</span><span class="p">,</span> <span class="p">[]</span><span class="nx">ErrorResp</span><span class="p">{</span>
</span></span><span class="line"><span class="cl"> <span class="p">{</span>
</span></span><span class="line"><span class="cl"> <span class="nx">Status</span><span class="p">:</span> <span class="nx">http</span><span class="p">.</span><span class="nx">StatusBadRequest</span><span class="p">,</span>
</span></span><span class="line"><span class="cl"> <span class="nx">Msg</span><span class="p">:</span> <span class="nx">fmt</span><span class="p">.</span><span class="nf">Sprintf</span><span class="p">(</span><span class="s">"failed to parse request: %v"</span><span class="p">,</span> <span class="nx">err</span><span class="p">),</span>
</span></span><span class="line"><span class="cl"> <span class="p">},</span>
</span></span><span class="line"><span class="cl"> <span class="p">})</span>
</span></span><span class="line"><span class="cl">
</span></span><span class="line"><span class="cl"> <span class="k">return</span>
</span></span><span class="line"><span class="cl"> <span class="p">}</span>
</span></span><span class="line"><span class="cl">
</span></span><span class="line"><span class="cl"> <span class="nx">res</span><span class="p">,</span> <span class="nx">errs</span> <span class="o">:=</span> <span class="nf">fn</span><span class="p">(</span><span class="nx">r</span><span class="p">.</span><span class="nf">Context</span><span class="p">(),</span> <span class="nx">v</span><span class="p">)</span>
</span></span><span class="line"><span class="cl"> <span class="nf">writeJSONResp</span><span class="p">(</span><span class="nx">w</span><span class="p">,</span> <span class="nx">successCode</span><span class="p">,</span> <span class="nx">res</span><span class="p">,</span> <span class="nx">errs</span><span class="p">)</span>
</span></span><span class="line"><span class="cl"> <span class="p">}</span>
</span></span><span class="line"><span class="cl"><span class="p">}</span>
</span></span><span class="line"><span class="cl">
</span></span><span class="line"><span class="cl"><span class="kd">func</span> <span class="nx">writeJSONResp</span><span class="p">[</span><span class="nx">T</span> <span class="nx">any</span><span class="p">](</span><span class="nx">w</span> <span class="nx">http</span><span class="p">.</span><span class="nx">ResponseWriter</span><span class="p">,</span> <span class="nx">successCode</span> <span class="kt">int</span><span class="p">,</span> <span class="nx">res</span> <span class="p">[]</span><span class="nx">T</span><span class="p">,</span> <span class="nx">errs</span> <span class="p">[]</span><span class="nx">ErrorResp</span><span class="p">)</span> <span class="p">{</span>
</span></span><span class="line"><span class="cl"> <span class="nx">body</span> <span class="o">:=</span> <span class="nx">JSONResp</span><span class="p">[</span><span class="nx">T</span><span class="p">]{</span>
</span></span><span class="line"><span class="cl"> <span class="nx">Resources</span><span class="p">:</span> <span class="nx">res</span><span class="p">,</span>
</span></span><span class="line"><span class="cl"> <span class="nx">Errs</span><span class="p">:</span> <span class="nx">errs</span><span class="p">,</span>
</span></span><span class="line"><span class="cl"> <span class="p">}</span>
</span></span><span class="line"><span class="cl">
</span></span><span class="line"><span class="cl"> <span class="nx">status</span> <span class="o">:=</span> <span class="nx">successCode</span>
</span></span><span class="line"><span class="cl"> <span class="k">for</span> <span class="nx">_</span><span class="p">,</span> <span class="nx">e</span> <span class="o">:=</span> <span class="k">range</span> <span class="nx">errs</span> <span class="p">{</span>
</span></span><span class="line"><span class="cl"> <span class="k">if</span> <span class="nx">e</span><span class="p">.</span><span class="nx">Status</span> <span class="p">></span> <span class="nx">status</span> <span class="p">{</span>
</span></span><span class="line"><span class="cl"> <span class="nx">status</span> <span class="p">=</span> <span class="nx">e</span><span class="p">.</span><span class="nx">Status</span>
</span></span><span class="line"><span class="cl"> <span class="p">}</span>
</span></span><span class="line"><span class="cl"> <span class="p">}</span>
</span></span><span class="line"><span class="cl"> <span class="nx">w</span><span class="p">.</span><span class="nf">Header</span><span class="p">().</span><span class="nf">Set</span><span class="p">(</span><span class="s">"Content-Type"</span><span class="p">,</span> <span class="s">"application/json"</span><span class="p">)</span>
</span></span><span class="line"><span class="cl"> <span class="nx">w</span><span class="p">.</span><span class="nf">WriteHeader</span><span class="p">(</span><span class="nx">status</span><span class="p">)</span>
</span></span><span class="line"><span class="cl"> <span class="nx">json</span><span class="p">.</span><span class="nf">NewEncoder</span><span class="p">(</span><span class="nx">w</span><span class="p">).</span><span class="nf">Encode</span><span class="p">(</span><span class="nx">body</span><span class="p">)</span>
</span></span><span class="line"><span class="cl"><span class="p">}</span>
</span></span></code></pre>
<p>And we’ve standardised all <code>POST</code> requests!</p>
<p>This function can be used by all <code>POST</code> requests, ensuring they adhere to the spec. It also removes the repetitive code around marshalling and unmarshalling to <code>JSON</code> and handles errors in a consistent manner.
The handler functions accept a <code>context</code> param and their expected struct input.</p>
<pre tabindex="0" class="chroma"><code><span class="line"><span class="cl"><span class="kd">func</span> <span class="p">(</span><span class="nx">s</span> <span class="o">*</span><span class="nx">Server</span><span class="p">)</span> <span class="nf">Register</span><span class="p">(</span><span class="nx">mux</span> <span class="o">*</span><span class="nx">http</span><span class="p">.</span><span class="nx">ServeMux</span><span class="p">)</span> <span class="p">{</span>
</span></span><span class="line"><span class="cl"><span class="o">...</span>
</span></span><span class="line"><span class="cl"> <span class="nx">mux</span><span class="p">.</span><span class="nf">HandleFunc</span><span class="p">(</span><span class="s">"POST /"</span><span class="p">,</span> <span class="nf">Post</span><span class="p">(</span><span class="mi">201</span><span class="p">,</span> <span class="nx">s</span><span class="p">.</span><span class="nx">Post</span><span class="p">))</span>
</span></span><span class="line"><span class="cl"><span class="p">}</span>
</span></span><span class="line"><span class="cl">
</span></span><span class="line"><span class="cl"><span class="kd">func</span> <span class="p">(</span><span class="nx">s</span> <span class="o">*</span><span class="nx">Server</span><span class="p">)</span> <span class="nf">Post</span><span class="p">(</span><span class="nx">ctx</span> <span class="nx">context</span><span class="p">.</span><span class="nx">Context</span><span class="p">,</span> <span class="nx">req</span> <span class="nx">ContentPostReq</span><span class="p">)</span> <span class="p">([]</span><span class="nx">Content</span><span class="p">,</span> <span class="p">[]</span><span class="nx">ErrorResp</span><span class="p">)</span> <span class="p">{</span>
</span></span><span class="line"><span class="cl"> <span class="nx">id</span> <span class="o">:=</span> <span class="nb">len</span><span class="p">(</span><span class="nx">s</span><span class="p">.</span><span class="nx">data</span><span class="p">)</span>
</span></span><span class="line"><span class="cl"> <span class="nx">content</span> <span class="o">:=</span> <span class="nx">Content</span><span class="p">{</span>
</span></span><span class="line"><span class="cl"> <span class="nx">ID</span><span class="p">:</span> <span class="nx">id</span><span class="p">,</span>
</span></span><span class="line"><span class="cl"> <span class="nx">Foo</span><span class="p">:</span> <span class="nx">req</span><span class="p">.</span><span class="nx">Foo</span><span class="p">,</span>
</span></span><span class="line"><span class="cl"> <span class="p">}</span>
</span></span><span class="line"><span class="cl"> <span class="nx">s</span><span class="p">.</span><span class="nx">data</span><span class="p">[</span><span class="nx">id</span><span class="p">]</span> <span class="p">=</span> <span class="nx">content</span>
</span></span><span class="line"><span class="cl">
</span></span><span class="line"><span class="cl"> <span class="k">return</span> <span class="p">[]</span><span class="nx">Content</span><span class="p">{</span><span class="nx">content</span><span class="p">},</span> <span class="kc">nil</span>
</span></span><span class="line"><span class="cl"><span class="p">}</span>
</span></span></code></pre>
<p>As you can see, the post function is fairly cleaner now.</p>
<p>You can extend this to all the other request types. If you have query or path parameters, you could either pass in the request, write a custom struct tag parser, or find someone else who has already done it: <a href="https://github.com/gorilla/schema">https://github.com/gorilla/schema</a>.</p>
<footer>
<br />
<hr />
<br />
<p>see something you disagree with? email: <a href="mailto:[email protected]">[email protected]</a></p>
</footer>
</main>
</body>
</html>
|
