-
Notifications
You must be signed in to change notification settings - Fork 8
/
json.html
397 lines (313 loc) · 22 KB
/
json.html
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
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>Go by Example 中文版: JSON</title>
<link rel=stylesheet href="site.css">
</head>
<script>
onkeydown = (e) => {
if (e.key == "ArrowLeft") {
window.location.href = 'regular-expressions';
}
if (e.key == "ArrowRight") {
window.location.href = 'xml';
}
}
</script>
<body>
<div class="example" id="json">
<h2><a href="./">Go by Example 中文版</a>: JSON</h2>
<table>
<tr>
<td class="docs">
<p>Go 提供内建的 JSON 编码解码（序列化反序列化）支持，
包括内建及自定义类型与 JSON 数据之间的转化。</p>
</td>
<td class="code empty leading">
</td>
</tr>
<tr>
<td class="docs">
</td>
<td class="code leading">
<a href="https://play.studygolang.com/p/yc_347liZME"><img title="Run code" src="play.png" class="run" /></a><img title="Copy code" src="clipboard.png" class="copy" />
<pre class="chroma"><span class="kn">package</span> <span class="nx">main</span>
</pre>
</td>
</tr>
<tr>
<td class="docs">
</td>
<td class="code leading">
<pre class="chroma"><span class="kn">import</span> <span class="p">(</span>
<span class="s">"encoding/json"</span>
<span class="s">"fmt"</span>
<span class="s">"os"</span>
<span class="p">)</span>
</pre>
</td>
</tr>
<tr>
<td class="docs">
<p>下面我们将使用这两个结构体来演示自定义类型的编码和解码。</p>
</td>
<td class="code leading">
<pre class="chroma">
<span class="kd">type</span> <span class="nx">response1</span> <span class="kd">struct</span> <span class="p">{</span>
<span class="nx">Page</span> <span class="kt">int</span>
<span class="nx">Fruits</span> <span class="p">[]</span><span class="kt">string</span>
<span class="p">}</span>
</pre>
</td>
</tr>
<tr>
<td class="docs">
<p>只有 <code>可导出</code> 的字段才会被 JSON 编码/解码。必须以大写字母开头的字段才是可导出的。</p>
</td>
<td class="code leading">
<pre class="chroma">
<span class="kd">type</span> <span class="nx">response2</span> <span class="kd">struct</span> <span class="p">{</span>
<span class="nx">Page</span> <span class="kt">int</span> <span class="s">`json:"page"`</span>
<span class="nx">Fruits</span> <span class="p">[]</span><span class="kt">string</span> <span class="s">`json:"fruits"`</span>
<span class="p">}</span>
</pre>
</td>
</tr>
<tr>
<td class="docs">
</td>
<td class="code leading">
<pre class="chroma"><span class="kd">func</span> <span class="nf">main</span><span class="p">()</span> <span class="p">{</span>
</pre>
</td>
</tr>
<tr>
<td class="docs">
<p>首先我们来看一下基本数据类型到 JSON 字符串的编码过程。
这是一些原子值的例子。</p>
</td>
<td class="code leading">
<pre class="chroma">
<span class="nx">bolB</span><span class="p">,</span> <span class="nx">_</span> <span class="o">:=</span> <span class="nx">json</span><span class="p">.</span><span class="nf">Marshal</span><span class="p">(</span><span class="kc">true</span><span class="p">)</span>
<span class="nx">fmt</span><span class="p">.</span><span class="nf">Println</span><span class="p">(</span><span class="nb">string</span><span class="p">(</span><span class="nx">bolB</span><span class="p">))</span>
</pre>
</td>
</tr>
<tr>
<td class="docs">
</td>
<td class="code leading">
<pre class="chroma"> <span class="nx">intB</span><span class="p">,</span> <span class="nx">_</span> <span class="o">:=</span> <span class="nx">json</span><span class="p">.</span><span class="nf">Marshal</span><span class="p">(</span><span class="mi">1</span><span class="p">)</span>
<span class="nx">fmt</span><span class="p">.</span><span class="nf">Println</span><span class="p">(</span><span class="nb">string</span><span class="p">(</span><span class="nx">intB</span><span class="p">))</span>
</pre>
</td>
</tr>
<tr>
<td class="docs">
</td>
<td class="code leading">
<pre class="chroma"> <span class="nx">fltB</span><span class="p">,</span> <span class="nx">_</span> <span class="o">:=</span> <span class="nx">json</span><span class="p">.</span><span class="nf">Marshal</span><span class="p">(</span><span class="mf">2.34</span><span class="p">)</span>
<span class="nx">fmt</span><span class="p">.</span><span class="nf">Println</span><span class="p">(</span><span class="nb">string</span><span class="p">(</span><span class="nx">fltB</span><span class="p">))</span>
</pre>
</td>
</tr>
<tr>
<td class="docs">
</td>
<td class="code leading">
<pre class="chroma"> <span class="nx">strB</span><span class="p">,</span> <span class="nx">_</span> <span class="o">:=</span> <span class="nx">json</span><span class="p">.</span><span class="nf">Marshal</span><span class="p">(</span><span class="s">"gopher"</span><span class="p">)</span>
<span class="nx">fmt</span><span class="p">.</span><span class="nf">Println</span><span class="p">(</span><span class="nb">string</span><span class="p">(</span><span class="nx">strB</span><span class="p">))</span>
</pre>
</td>
</tr>
<tr>
<td class="docs">
<p>这是一些切片和 map 编码成 JSON 数组和对象的例子。</p>
</td>
<td class="code leading">
<pre class="chroma">
<span class="nx">slcD</span> <span class="o">:=</span> <span class="p">[]</span><span class="kt">string</span><span class="p">{</span><span class="s">"apple"</span><span class="p">,</span> <span class="s">"peach"</span><span class="p">,</span> <span class="s">"pear"</span><span class="p">}</span>
<span class="nx">slcB</span><span class="p">,</span> <span class="nx">_</span> <span class="o">:=</span> <span class="nx">json</span><span class="p">.</span><span class="nf">Marshal</span><span class="p">(</span><span class="nx">slcD</span><span class="p">)</span>
<span class="nx">fmt</span><span class="p">.</span><span class="nf">Println</span><span class="p">(</span><span class="nb">string</span><span class="p">(</span><span class="nx">slcB</span><span class="p">))</span>
</pre>
</td>
</tr>
<tr>
<td class="docs">
</td>
<td class="code leading">
<pre class="chroma"> <span class="nx">mapD</span> <span class="o">:=</span> <span class="kd">map</span><span class="p">[</span><span class="kt">string</span><span class="p">]</span><span class="kt">int</span><span class="p">{</span><span class="s">"apple"</span><span class="p">:</span> <span class="mi">5</span><span class="p">,</span> <span class="s">"lettuce"</span><span class="p">:</span> <span class="mi">7</span><span class="p">}</span>
<span class="nx">mapB</span><span class="p">,</span> <span class="nx">_</span> <span class="o">:=</span> <span class="nx">json</span><span class="p">.</span><span class="nf">Marshal</span><span class="p">(</span><span class="nx">mapD</span><span class="p">)</span>
<span class="nx">fmt</span><span class="p">.</span><span class="nf">Println</span><span class="p">(</span><span class="nb">string</span><span class="p">(</span><span class="nx">mapB</span><span class="p">))</span>
</pre>
</td>
</tr>
<tr>
<td class="docs">
<p>JSON 包可以自动的编码你的自定义类型。
编码的输出只包含可导出的字段，并且默认使用字段名作为 JSON 数据的键名。</p>
</td>
<td class="code leading">
<pre class="chroma">
<span class="nx">res1D</span> <span class="o">:=</span> <span class="o">&</span><span class="nx">response1</span><span class="p">{</span>
<span class="nx">Page</span><span class="p">:</span> <span class="mi">1</span><span class="p">,</span>
<span class="nx">Fruits</span><span class="p">:</span> <span class="p">[]</span><span class="kt">string</span><span class="p">{</span><span class="s">"apple"</span><span class="p">,</span> <span class="s">"peach"</span><span class="p">,</span> <span class="s">"pear"</span><span class="p">}}</span>
<span class="nx">res1B</span><span class="p">,</span> <span class="nx">_</span> <span class="o">:=</span> <span class="nx">json</span><span class="p">.</span><span class="nf">Marshal</span><span class="p">(</span><span class="nx">res1D</span><span class="p">)</span>
<span class="nx">fmt</span><span class="p">.</span><span class="nf">Println</span><span class="p">(</span><span class="nb">string</span><span class="p">(</span><span class="nx">res1B</span><span class="p">))</span>
</pre>
</td>
</tr>
<tr>
<td class="docs">
<p>你可以给结构字段声明标签来自定义编码的 JSON 数据的键名。
上面 <code>Response2</code> 的定义，就是这种标签的一个例子。</p>
</td>
<td class="code leading">
<pre class="chroma">
<span class="nx">res2D</span> <span class="o">:=</span> <span class="o">&</span><span class="nx">response2</span><span class="p">{</span>
<span class="nx">Page</span><span class="p">:</span> <span class="mi">1</span><span class="p">,</span>
<span class="nx">Fruits</span><span class="p">:</span> <span class="p">[]</span><span class="kt">string</span><span class="p">{</span><span class="s">"apple"</span><span class="p">,</span> <span class="s">"peach"</span><span class="p">,</span> <span class="s">"pear"</span><span class="p">}}</span>
<span class="nx">res2B</span><span class="p">,</span> <span class="nx">_</span> <span class="o">:=</span> <span class="nx">json</span><span class="p">.</span><span class="nf">Marshal</span><span class="p">(</span><span class="nx">res2D</span><span class="p">)</span>
<span class="nx">fmt</span><span class="p">.</span><span class="nf">Println</span><span class="p">(</span><span class="nb">string</span><span class="p">(</span><span class="nx">res2B</span><span class="p">))</span>
</pre>
</td>
</tr>
<tr>
<td class="docs">
<p>现在来看看将 JSON 数据解码为 Go 值的过程。
这是一个普通数据结构的解码例子。</p>
</td>
<td class="code leading">
<pre class="chroma">
<span class="nx">byt</span> <span class="o">:=</span> <span class="p">[]</span><span class="nb">byte</span><span class="p">(</span><span class="s">`{"num":6.13,"strs":["a","b"]}`</span><span class="p">)</span>
</pre>
</td>
</tr>
<tr>
<td class="docs">
<p>我们需要提供一个 JSON 包可以存放解码数据的变量。
这里的 <code>map[string]interface{}</code> 是一个键为 string，值为任意值的 map。</p>
</td>
<td class="code leading">
<pre class="chroma">
<span class="kd">var</span> <span class="nx">dat</span> <span class="kd">map</span><span class="p">[</span><span class="kt">string</span><span class="p">]</span><span class="kd">interface</span><span class="p">{}</span>
</pre>
</td>
</tr>
<tr>
<td class="docs">
<p>这是实际的解码，以及相关错误的检查。</p>
</td>
<td class="code leading">
<pre class="chroma">
<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">Unmarshal</span><span class="p">(</span><span class="nx">byt</span><span class="p">,</span> <span class="o">&</span><span class="nx">dat</span><span class="p">);</span> <span class="nx">err</span> <span class="o">!=</span> <span class="kc">nil</span> <span class="p">{</span>
<span class="nb">panic</span><span class="p">(</span><span class="nx">err</span><span class="p">)</span>
<span class="p">}</span>
<span class="nx">fmt</span><span class="p">.</span><span class="nf">Println</span><span class="p">(</span><span class="nx">dat</span><span class="p">)</span>
</pre>
</td>
</tr>
<tr>
<td class="docs">
<p>为了使用解码 map 中的值，我们需要将他们进行适当的类型转换。
例如，这里我们将 <code>num</code> 的值转换成 <code>float64</code> 类型。</p>
</td>
<td class="code leading">
<pre class="chroma">
<span class="nx">num</span> <span class="o">:=</span> <span class="nx">dat</span><span class="p">[</span><span class="s">"num"</span><span class="p">].(</span><span class="kt">float64</span><span class="p">)</span>
<span class="nx">fmt</span><span class="p">.</span><span class="nf">Println</span><span class="p">(</span><span class="nx">num</span><span class="p">)</span>
</pre>
</td>
</tr>
<tr>
<td class="docs">
<p>访问嵌套的值需要一系列的转化。</p>
</td>
<td class="code leading">
<pre class="chroma">
<span class="nx">strs</span> <span class="o">:=</span> <span class="nx">dat</span><span class="p">[</span><span class="s">"strs"</span><span class="p">].([]</span><span class="kd">interface</span><span class="p">{})</span>
<span class="nx">str1</span> <span class="o">:=</span> <span class="nx">strs</span><span class="p">[</span><span class="mi">0</span><span class="p">].(</span><span class="kt">string</span><span class="p">)</span>
<span class="nx">fmt</span><span class="p">.</span><span class="nf">Println</span><span class="p">(</span><span class="nx">str1</span><span class="p">)</span>
</pre>
</td>
</tr>
<tr>
<td class="docs">
<p>我们还可以将 JSON 解码为自定义数据类型。
这样做的好处是，可以为我们的程序增加附加的类型安全性，
并在访问解码后的数据时不需要类型断言。</p>
</td>
<td class="code leading">
<pre class="chroma">
<span class="nx">str</span> <span class="o">:=</span> <span class="s">`{"page": 1, "fruits": ["apple", "peach"]}`</span>
<span class="nx">res</span> <span class="o">:=</span> <span class="nx">response2</span><span class="p">{}</span>
<span class="nx">json</span><span class="p">.</span><span class="nf">Unmarshal</span><span class="p">([]</span><span class="nb">byte</span><span class="p">(</span><span class="nx">str</span><span class="p">),</span> <span class="o">&</span><span class="nx">res</span><span class="p">)</span>
<span class="nx">fmt</span><span class="p">.</span><span class="nf">Println</span><span class="p">(</span><span class="nx">res</span><span class="p">)</span>
<span class="nx">fmt</span><span class="p">.</span><span class="nf">Println</span><span class="p">(</span><span class="nx">res</span><span class="p">.</span><span class="nx">Fruits</span><span class="p">[</span><span class="mi">0</span><span class="p">])</span>
</pre>
</td>
</tr>
<tr>
<td class="docs">
<p>在上面例子的标准输出上，
我们总是使用 byte和 string 作为数据和 JSON 表示形式之间的中介。
当然，我们也可以像 <code>os.Stdout</code> 一样直接将 JSON 编码流传输到
<code>os.Writer</code> 甚至 HTTP 响应体。</p>
</td>
<td class="code">
<pre class="chroma">
<span class="nx">enc</span> <span class="o">:=</span> <span class="nx">json</span><span class="p">.</span><span class="nf">NewEncoder</span><span class="p">(</span><span class="nx">os</span><span class="p">.</span><span class="nx">Stdout</span><span class="p">)</span>
<span class="nx">d</span> <span class="o">:=</span> <span class="kd">map</span><span class="p">[</span><span class="kt">string</span><span class="p">]</span><span class="kt">int</span><span class="p">{</span><span class="s">"apple"</span><span class="p">:</span> <span class="mi">5</span><span class="p">,</span> <span class="s">"lettuce"</span><span class="p">:</span> <span class="mi">7</span><span class="p">}</span>
<span class="nx">enc</span><span class="p">.</span><span class="nf">Encode</span><span class="p">(</span><span class="nx">d</span><span class="p">)</span>
<span class="p">}</span>
</pre>
</td>
</tr>
</table>
<table>
<tr>
<td class="docs">
</td>
<td class="code leading">
<pre class="chroma"><span class="gp">$</span> go run json.go
<span class="go">true
</span><span class="go">1
</span><span class="go">2.34
</span><span class="go">"gopher"
</span><span class="go">["apple","peach","pear"]
</span><span class="go">{"apple":5,"lettuce":7}
</span><span class="go">{"Page":1,"Fruits":["apple","peach","pear"]}
</span><span class="go">{"page":1,"fruits":["apple","peach","pear"]}
</span><span class="go">map[num:6.13 strs:[a b]]
</span><span class="go">6.13
</span><span class="go">a
</span><span class="go">{1 [apple peach]}
</span><span class="go">apple
</span><span class="go">{"apple":5,"lettuce":7}</span></pre>
</td>
</tr>
<tr>
<td class="docs">
<p>至此，我们已经学习了基本的 Go JSON 知识，如果想要获取更多的信息，
请查阅 <a href="http://blog.golang.org/2011/01/json-and-go.html">JSON and Go</a> 博文
和 <a href="http://golang.org/pkg/encoding/json/">JSON package docs</a>。</p>
</td>
<td class="code empty">
</td>
</tr>
</table>
<p class="next">
下一个例子: <a href="xml">XML</a>
</p>
<p class="footer">
<a href="https://twitter.com/mmcgrana">@mmcgrana</a> 和<a href="https://eli.thegreenplace.net">Eli Bendersky</a>编写 | <a href="https://github.com/gobyexample-cn">gobyexample-cn</a> 翻译 | <a href="https://github.com/gobyexample-cn/gobyexample/issues">反馈</a> | <a href="https://github.com/gobyexample-cn/gobyexample">源码</a> | <a href="https://github.com/mmcgrana/gobyexample#license">license</a> </p>
</p>
</div>
<script>
var codeLines = [];
codeLines.push('');codeLines.push('package main\u000A');codeLines.push('import (\u000A \"encoding/json\"\u000A \"fmt\"\u000A \"os\"\u000A)\u000A');codeLines.push('type response1 struct {\u000A Page int\u000A Fruits []string\u000A}\u000A');codeLines.push('type response2 struct {\u000A Page int `json:\"page\"`\u000A Fruits []string `json:\"fruits\"`\u000A}\u000A');codeLines.push('func main() {\u000A');codeLines.push(' bolB, _ :\u003D json.Marshal(true)\u000A fmt.Println(string(bolB))\u000A');codeLines.push(' intB, _ :\u003D json.Marshal(1)\u000A fmt.Println(string(intB))\u000A');codeLines.push(' fltB, _ :\u003D json.Marshal(2.34)\u000A fmt.Println(string(fltB))\u000A');codeLines.push(' strB, _ :\u003D json.Marshal(\"gopher\")\u000A fmt.Println(string(strB))\u000A');codeLines.push(' slcD :\u003D []string{\"apple\", \"peach\", \"pear\"}\u000A slcB, _ :\u003D json.Marshal(slcD)\u000A fmt.Println(string(slcB))\u000A');codeLines.push(' mapD :\u003D map[string]int{\"apple\": 5, \"lettuce\": 7}\u000A mapB, _ :\u003D json.Marshal(mapD)\u000A fmt.Println(string(mapB))\u000A');codeLines.push(' res1D :\u003D \u0026response1{\u000A Page: 1,\u000A Fruits: []string{\"apple\", \"peach\", \"pear\"}}\u000A res1B, _ :\u003D json.Marshal(res1D)\u000A fmt.Println(string(res1B))\u000A');codeLines.push(' res2D :\u003D \u0026response2{\u000A Page: 1,\u000A Fruits: []string{\"apple\", \"peach\", \"pear\"}}\u000A res2B, _ :\u003D json.Marshal(res2D)\u000A fmt.Println(string(res2B))\u000A');codeLines.push(' byt :\u003D []byte(`{\"num\":6.13,\"strs\":[\"a\",\"b\"]}`)\u000A');codeLines.push(' var dat map[string]interface{}\u000A');codeLines.push(' if err :\u003D json.Unmarshal(byt, \u0026dat); err !\u003D nil {\u000A panic(err)\u000A }\u000A fmt.Println(dat)\u000A');codeLines.push(' num :\u003D dat[\"num\"].(float64)\u000A fmt.Println(num)\u000A');codeLines.push(' strs :\u003D dat[\"strs\"].([]interface{})\u000A str1 :\u003D strs[0].(string)\u000A fmt.Println(str1)\u000A');codeLines.push(' str :\u003D `{\"page\": 1, \"fruits\": [\"apple\", \"peach\"]}`\u000A res :\u003D response2{}\u000A json.Unmarshal([]byte(str), \u0026res)\u000A fmt.Println(res)\u000A fmt.Println(res.Fruits[0])\u000A');codeLines.push(' enc :\u003D json.NewEncoder(os.Stdout)\u000A d :\u003D map[string]int{\"apple\": 5, \"lettuce\": 7}\u000A enc.Encode(d)\u000A}\u000A');codeLines.push('');codeLines.push('');
</script>
<script src="site.js" async></script>
</body>
</html>