怎么用C语言获取JSON中的数据？

用C语言获取JSON中的数据的方法是使用 CJSON。

以下简单介绍用CJSON的思路及实现：

1）创建json，从json中获取数据。

#nclude <stdio.h>

#include "cJSON.h"

char * makeJson()

{

cJSON * pJsonRoot = NULL

pJsonRoot = cJSON_CreateObject()

if(NULL == pJsonRoot)

{

//error happend here

return NULL

}

cJSON_AddStringToObject(pJsonRoot, "hello", "hello world")

cJSON_AddNumberToObject(pJsonRoot, "number", 10010)

cJSON_AddBoolToObject(pJsonRoot, "bool", 1)

cJSON * pSubJson = NULL

pSubJson = cJSON_CreateObject()

if(NULL == pSubJson)

{

// create object faild, exit

cJSON_Delete(pJsonRoot)

return NULL

}

cJSON_AddStringToObject(pSubJson, "subjsonobj", "a sub json string")

cJSON_AddItemToObject(pJsonRoot, "subobj", pSubJson)

char * p = cJSON_Print(pJsonRoot)

// else use :

// char * p = cJSON_PrintUnformatted(pJsonRoot)

if(NULL == p)

{

//convert json list to string faild, exit

//because sub json pSubJson han been add to pJsonRoot, so just delete pJsonRoot, if you also delete pSubJson, it will coredump, and error is : double free

cJSON_Delete(pJsonRoot)

return NULL

}

//free(p)

cJSON_Delete(pJsonRoot)

return p

}

void parseJson(char * pMsg)

{

if(NULL == pMsg)

{

return

}

cJSON * pJson = cJSON_Parse(pMsg)；

if(NULL == pJson)

{

// parse faild, return

return

}

// get string from json

cJSON * pSub = cJSON_GetObjectItem(pJson, "hello")

if(NULL == pSub)

{

//get object named "hello" faild

}

printf("obj_1 : %s\n", pSub->valuestring)

// get number from json

pSub = cJSON_GetObjectItem(pJson, "number")

if(NULL == pSub)

{

//get number from json faild

}

printf("obj_2 : %d\n", pSub->valueint)

// get bool from json

pSub = cJSON_GetObjectItem(pJson, "bool")

if(NULL == pSub)

{

// get bool from json faild

}

printf("obj_3 : %d\n", pSub->valueint)

// get sub object

pSub = cJSON_GetObjectItem(pJson, "subobj")

if(NULL == pSub)

{

// get sub object faild

}

cJSON * pSubSub = cJSON_GetObjectItem(pSub, "subjsonobj")

if(NULL == pSubSub)

{

// get object from subject object faild

}

printf("sub_obj_1 : %s\n", pSubSub->valuestring)

cJSON_Delete(pJson)

}

int main()

{

char * p = makeJson()

if(NULL == p)

{

return 0

}

printf("%s\n", p)

parseJson(p)

free(p)//这里不要忘记释放内存，cJSON_Print()函数或者cJSON_PrintUnformatted（）产生的内存，使用free(char *)进行释放

return 0

}

2）创建json数组和解析json数组

//创建数组，数组值是另一个JSON的item，这里使用数字作为演示

char * makeArray(int iSize)

{

cJSON * root = cJSON_CreateArray()

if(NULL == root)

{

printf("create json array faild\n")

return NULL

}

int i = 0

for(i = 0i <iSizei++)

{

cJSON_AddNumberToObject(root, "hehe", i)

}

char * out = cJSON_Print(root)

cJSON_Delete(root)

return out

}

//解析刚刚的CJSON数组

void parseArray(char * pJson)

{

if(NULL == pJson)

{

return

}

cJSON * root = NULL

if((root = cJSON_Parse(pJson)) == NULL)

{

return

}

int iSize = cJSON_GetArraySize(root)

for(int iCnt = 0iCnt <iSizeiCnt++)

{

cJSON * pSub = cJSON_GetArrayItem(root, iCnt)

if(NULL == pSub)

{

continue

}

int iValue = pSub->valueint

printf("value[%2d] : [%d]\n", iCnt, iValue)

}

cJSON_Delete(root)

return

}

有两种方法：

一是标准的输出输入方式 比如新建一个磁盘文件c:\a.txt， 将键盘输入的一字符串写到文件中：

FILE *ft

char str[50]

ft=fopen("c:\\a.txt","w+")

printf("输入一个字符串：")

scanf("%s",str)

fputs(str,ft)

fclose(ft)

//重新打开这个文件并读出字符串，显示在屏幕上 ft=fopen("c:\\a.txt","rt")

fgets(str,50,ft)

fclose(ft)printf("%s",str)

二是低级输入输出方式 仍如上例：

int hdchar str[50]printf("输入一个字符串：")

scanf("%s",str)

hd=open("c:\\a.txt",O_CREAT|O_TEXT|O_WRONLY)

write(hd,str,strlen(str))

close(hd)//重新打开这个文件并读出字符串，显示在屏幕上。

hd=open("c:\\a.txt",O_TEXT|O_RDONLY)read(hd,str,50)

close(hd)printf("%s",str)。

(1) 将如下代码copy之后保存为 server.js

(2) 然后执行: node server.js

var http = require('http')

var url = require('url')

// 访问的json地址与返回的json数据映射关系

var array=[

{

url:'/signup/index.json',

json:'{"tasks":[{"finishType":"人数优先","gmtEnd":"2015-11-19 11:30:00","gmtStart":"2015-11-17 11:30:00","id":98,"memo":"招新任务01","name":"招新任务01","requireNum":10,"signedupNum":0,"signupStatus":"","taskStatus":"进行中"}],"stat":"ok"}'

},

{

url:'/signup/applyCheck.json',

json:'{"signupInfo":{"alipayAccount":"20881021179902510156","alipayCardNo":"2088102117990251","birthday":"","certifyStatus":null,"city":"","college":"","email":"rjmuqiang@gmail.com","gender":null,"gmtCreate":null,"gmtModified":null,"id":2,"identityCardNo":"330283198903120025","identityCardPic":"","major":"","maxWeekHours":0,"minWeekHours":0,"mobile":"18905818799","province":"","qualificationPic":"","realName":"zhulu","recruitSource":"","signupTaskId":98,"status":null,"statusReason":"","student":false,"testScore":0,"trainScore":0},"checkResult":{"code":"SUCCESS","message":"处理成功","printResult":true,"success":true},"stat":"ok"}'

},

{

url:'/server/matchSuggest.json',

json:'{"TotalHits":88,"errorCode":0,"errorDesc":"no_error","MatchResults":[{"CatId":"4098","CatTitlePath":"%E5%86%85%E9%83%A8%E7%9F%A5%E8%AF%86%E5%BA%93%3E%E8%B4%A6%E6%88%B7%E5%9F%BA%E7%A1%80%E5%8F%8A%E8%B5%84%E4%BA%A7%E7%AE%A1%E7%90%86%EF%BC%88%E6%96%B0%EF%BC%89%3E%E8%B4%A6%E6%88%B7%E5%9F%BA%E7%A1%80%3E%E5%AF%86%E7%A0%81%3E%E6%89%8B%E5%8A%BF%E5%AF%86%E7%A0%81","ChannelNames":"","Content":"","CreatorName":"%E6%A1%83%E7%98%B4","GmtCreate":"2015-04-07 17:58:42","GmtModified":"2015-05-19 11:48:36","Id":"6056","Keywords":"","ModifierId":"12484","ModifierName":"%E7%89%A7%E6%9A%AE","Status":"PUBLISHED","Title":"%E9%80%9A%E8%BF%87%E6%94%AF%E4%BB%98%E5%AE%9D%E9%92%B1%E5%8C%85%EF%BC%8C%3Cfont+color%3Dred%3E%E5%BF%98%E8%AE%B0%3C%2Ffont%3E%E6%89%8B%E5%8A%BF%3Cfont+color%3Dred%3E%E5%AF%86%E7%A0%81%3C%2Ffont%3E%E7%9A%84%E5%A4%84%E7%90%86%E6%B5%81%E7%A8%8B","Type":"NORMAL","deleted":"N"}]}'

},

{

url:'/signup/signup.json',

json:'{"stat":"ok"}'

}

]

// var temResult='{"TotalHits":88,"errorCode":0,"errorDesc":"no_error","MatchResults":[{"CatId":"4098","CatTitlePath":"%E5%86%85%E9%83%A8%E7%9F%A5%E8%AF%86%E5%BA%93%3E%E8%B4%A6%E6%88%B7%E5%9F%BA%E7%A1%80%E5%8F%8A%E8%B5%84%E4%BA%A7%E7%AE%A1%E7%90%86%EF%BC%88%E6%96%B0%EF%BC%89%3E%E8%B4%A6%E6%88%B7%E5%9F%BA%E7%A1%80%3E%E5%AF%86%E7%A0%81%3E%E6%89%8B%E5%8A%BF%E5%AF%86%E7%A0%81","ChannelNames":"","Content":"%e7%87%95%e5%ad%90","CreatorName":"%E6%A1%83%E7%98%B4","GmtCreate":"2015-04-07 17:58:42","GmtModified":"2015-05-19 11:48:36","Id":"6056","Keywords":"","ModifierId":"12484","ModifierName":"%E7%89%A7%E6%9A%AE","Status":"PUBLISHED","Title":"%E9%80%9A%E8%BF%87%E6%94%AF%E4%BB%98%E5%AE%9D%E9%92%B1%E5%8C%85%EF%BC%8C%3Cfont+color%3Dred%3E%E5%BF%98%E8%AE%B0%3C%2Ffont%3E%E6%89%8B%E5%8A%BF%3Cfont+color%3Dred%3E%E5%AF%86%E7%A0%81%3C%2Ffont%3E%E7%9A%84%E5%A4%84%E7%90%86%E6%B5%81%E7%A8%8B","Type":"NORMAL","deleted":"N"},{"CatId":"4098","CatTitlePath":"%E5%86%85%E9%83%A8%E7%9F%A5%E8%AF%86%E5%BA%93%3E%E8%B4%A6%E6%88%B7%E5%9F%BA%E7%A1%80%E5%8F%8A%E8%B5%84%E4%BA%A7%E7%AE%A1%E7%90%86%EF%BC%88%E6%96%B0%EF%BC%89%3E%E8%B4%A6%E6%88%B7%E5%9F%BA%E7%A1%80%3E%E5%AF%86%E7%A0%81%3E%E6%89%8B%E5%8A%BF%E5%AF%86%E7%A0%81","ChannelNames":"","Content":"%e7%87%95%e7%aa%9d","CreatorName":"%E6%A1%83%E7%98%B4","GmtCreate":"2015-04-07 17:58:42","GmtModified":"2015-05-19 11:48:36","Id":"6056","Keywords":"","ModifierId":"12484","ModifierName":"%E7%89%A7%E6%9A%AE","Status":"PUBLISHED","Title":"%E9%80%9A%E8%BF%87%E6%94%AF%E4%BB%98%E5%AE%9D%E9%92%B1%E5%8C%85%EF%BC%8C%3Cfont+color%3Dred%3E%E5%BF%98%E8%AE%B0%3C%2Ffont%3E%E6%89%8B%E5%8A%BF%3Cfont+color%3Dred%3E%E5%AF%86%E7%A0%81%3C%2Ffont%3E%E7%9A%84%E5%A4%84%E7%90%86%E6%B5%81%E7%A8%8B","Type":"NORMAL","deleted":"N"}]}'

http.createServer(function(request, response){

response.writeHead(200,{

"Access-Control-Allow-Origin":"http://10.37.187.79:8000",

"Access-Control-Allow-Credentials": "true",

"Access-Control-Allow-Headers":"X-Requested-With",

"Access-Control-Allow-Methods":"PUT,POST,GET,DELETE,OPTIONS",

"X-Powered-By":"3.2.1",

"Content-Type":"application/jsoncharset=utf-8",

"Connection":"keep-alive"

})

var reqURL=request.url

var result=reqURL + " 对应的json结果数据是什么?请进行配置"

var i=array.length

while(i--){

if(reqURL.indexOf(array[i].url)==0){

result= array[i].json

}

console.log(111)

}

// var params = url.parse(request.url, true).query

// console.log(params)

response.write(result)

response.end()

}).listen(8787)

console.log('启动成功...')

=并不会把上一条覆盖，因为arr[i].name并不一样，相当于给json动态添加不同的属性。结果如下

当然，如果你数组中的那么如果会一样的话，那么就会被覆盖掉。如果是想要往一个新的对象上加，当作它的属性，那么属性名肯定是唯一的。如果你只是单纯的先把数组变成json串的话，可以使用JSON.stringify(),如下

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