JSON是一种轻量级的数据交互格式，易于人阅读和编写，同时也易于机器解析和生成，并有效地提升网络传输效率，实际项目中经常用到，相比xml有很多优点，问问度娘，优点一箩筐。

第三方库

json解析选用jsoncpp作为第三方库，jsoncpp使用广泛，c++开发首选。

jsoncpp目前已经托管到了github上，地址：https://github.com/open-source-parsers/jsoncpp

使用

使用c++进行构造json和解析json，选用vs2010作为IDE。工程中使用jsoncpp的源码进行编译，没有使用jsoncpp的库，为方便大家使用把dll和lib库也放到了我的工程jsoncpplib文件夹下，有需要的可以直接引用库。

待解析的json数据格式如下图：

/********************************************************
Copyright (C), 2016-2017,
FileName:     main
Author:     woniu201
Email:         wangpengfei.201@163.com
Created:     2017/09/06
Description:use jsoncpp src , not use dll, but i also provide dll and lib.
********************************************************/
 
#include "stdio.h"
#include <string>
#include "jsoncpp/json.h"
 
using namespace std;
 
/************************************
@ Brief:        read file
@ Author:        woniu201 
@ Created:         2017/09/06
@ Return:        file data  
************************************/
char *getfileAll(char *fname)
{
    FILE *fp;
    char *str;
    char txt[1000];
    int filesize;
    if ((fp=fopen(fname,"r"))==NULL){
        printf("open file %s fail \n",fname);
        return NULL;
    }
 
    fseek(fp,0,SEEK_END); 
 
    filesize = ftell(fp);
    str=(char *)malloc(filesize);
    str[0]=0;
 
    rewind(fp);
    while((fgets(txt,1000,fp))!=NULL){
        strcat(str,txt);
    }
    fclose(fp);
    return str;
}
 
/************************************
@ Brief:        write file
@ Author:        woniu201 
@ Created:         2017/09/06
@ Return:            
************************************/
int writefileAll(char* fname,const char* data)
{
    FILE *fp;
    if ((fp=fopen(fname, "w")) == NULL)
    {
        printf("open file %s fail \n", fname);
        return 1;
    }
    
    fprintf(fp, "%s", data);
    fclose(fp);
    
    return 0;
}
 
/************************************
@ Brief:        parse json data
@ Author:        woniu201 
@ Created:         2017/09/06
@ Return:            
************************************/
int parseJSON(const char* jsonstr)
{
    Json::Reader reader;
    Json::Value  resp;
 
    if (!reader.parse(jsonstr, resp, false))
    {
        printf("bad json format!\n");
        return 1;
    }
    int result = resp["Result"].asInt();
    string resultMessage = resp["ResultMessage"].asString();
    printf("Result=%d; ResultMessage=%s\n", result, resultMessage.c_str());
 
    Json::Value & resultValue = resp["ResultValue"];
    for (int i=0; i<resultValue.size(); i++)
    {
        Json::Value subJson = resultValue[i];
        string cpuRatio = subJson["cpuRatio"].asString();
        string serverIp = subJson["serverIp"].asString();
        string conNum = subJson["conNum"].asString();
        string websocketPort = subJson["websocketPort"].asString();
        string mqttPort = subJson["mqttPort"].asString();
        string ts = subJson["TS"].asString();
 
        printf("cpuRatio=%s; serverIp=%s; conNum=%s; websocketPort=%s; mqttPort=%s; ts=%s\n",cpuRatio.c_str(), serverIp.c_str(),
            conNum.c_str(), websocketPort.c_str(), mqttPort.c_str(), ts.c_str());
    }
    return 0;
}
 
/************************************
@ Brief:        create json data
@ Author:        woniu201 
@ Created:         2017/09/06
@ Return:            
************************************/
int createJSON()
{
    Json::Value req;
    req["Result"] = 1;
    req["ResultMessage"] = "200";
 
    Json::Value    object1;
    object1["cpuRatio"] = "4.04";
    object1["serverIp"] = "42.159.116.104";
    object1["conNum"] = "1";
    object1["websocketPort"] = "0";
    object1["mqttPort"] = "8883";
    object1["TS"] = "1504665880572";
    Json::Value    object2;
    object2["cpuRatio"] = "2.04";
    object2["serverIp"] = "42.159.122.251";
    object2["conNum"] = "2";
    object2["websocketPort"] = "0";
    object2["mqttPort"] = "8883";
    object2["TS"] = "1504665896981";
 
    Json::Value jarray;
    jarray.append(object1);
    jarray.append(object2);
 
    req["ResultValue"] = jarray;
 
    Json::FastWriter writer;
    string jsonstr = writer.write(req);
 
    printf("%s\n", jsonstr.c_str());
 
    writefileAll("createJson.json", jsonstr.c_str());
    return 0;
}
 
int main()
{
    char* json = getfileAll("parseJson.json");
    parseJSON(json);
    printf("===============================\n");
    createJSON();
 
    getchar();
    return 1;
}

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