C++構造和解析JSON

JSON是一種輕量級的數據交互格式，易於人閱讀和編寫，同時也易於機器解析和生成，並有效地提高網絡傳輸效率，實際項目中常常用到，相比xml有不少優勢，問問度娘，優勢一籮筐。

第三方庫

json解析選用jsoncpp做爲第三方庫，jsoncpp使用普遍，c++開發首選。

jsoncpp目前已經託管到了github上，地址：https://github.com/open-source-parsers/jsoncpp

使用

使用c++進行構造json和解析json，選用vs2010做爲IDE。工程中使用jsoncpp的源碼進行編譯，沒有使用jsoncpp的庫，爲方便你們使用把dll和lib庫也放到了個人工程jsoncpplib文件夾下，有須要的能夠直接引用庫。

待解析的json數據格式以下圖：

/********************************************************
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;
}

<font color=red size=3 face="宋體">關注下面公衆號，回覆"104"獲取源碼</font>