jsoncpp库使用例子

从json格式的字符串中解析读：

//g++ jsoncpp_read_sample.cpp -I/usr/local/include/jsoncpp -ljsoncpp

#include <iostream>  
#include <string>  
#include <json/json.h>


int main(void)  
{  
	std::string strjson = "{"key1":"value1","array":[{"key2":"value2"},{"key2":"value3"},{"key2":"value4"}]}";
/*
{	
	"key1":"value1","array":
	[
		{"key2":"value2"},{"key2":"value3"},{"key2":"value4"}
	]
}
*/  
	Json::Reader reader;  
	Json::Value root;  
	
	if (reader.parse(strjson,root))  
	{  
		std::string out = root["key1"].asString();  
		std::cout << out << std::endl;  
		const Json::Value arrayObj = root["array"];  
		for (int i=0; i<arrayObj.size(); i++)  
		{  
			out = arrayObj[i]["key2"].asString();  
			std::cout << out << std::endl;  
		}
	}
	
	return 0;  
} 

//g++ jsoncpp_write_sample.cpp -I/usr/local/include/jsoncpp -ljsoncpp

#include <iostream>  
#include <string>  
#include <json/json.h>


int main(void)  
{
	Json::Value root;  
	Json::Value arrayObj;  
	Json::Value item;  
	
	for (int i = 0; i < 10; i ++)  
	{  
		item["key"] = i;  
		arrayObj.append(item);  
	}  
	
	root["key1"] = "value1";  
	root["key2"] = "value2";  
	root["array"] = arrayObj;  
	//root.toStyledString();  
	//格式化输出Json格式内容
	std::string out = root.toStyledString();  
	std::cout << out << std::endl;  
	std::cout << "--------------------" << std::endl;
	
	//未格式化输出Json格式内容
	Json::FastWriter writer;
	std::string json_str = writer.write(root);
	std::cout << json_str << std::endl;  
	return 0;  
}

从json格式的文件中解析读：

文件内容为

{ 
	"mmac": "e4:95:6e:4e:ed:6e","wmac": "ff:ff:ff:ff:ff:ff","data": 
	[ 	{ "mac": "3c:46:d8:19:6a:e3","rssi": "-82","tmc": "ff:ff:ff:ff:ff:ff"	},{ "mac": "90:18:7c:f2:45:cc","rssi": "-71","tmc": "ff:ff:ff:ff:ff:ff" },{ "mac": "b8:44:d9:02:b0:94","rssi": "-86",{ "mac": "dc:85:de:6a:f8:37","rssi": "-44",{ "mac": "ec:0e:c4:60:b7:95","rssi": "-77","tmc": "ff:ff:ff:ff:ff:ff" } 
	] 
}

//g++ read_json_file.cpp -I/usr/local/include/jsoncpp -ljsoncpp

#include <fstream>
#include <iostream>  
#include <string>  
#include <cassert>
#include <json/json.h>

int main(void)  
{  
	std::ifstream ifs;
	
	ifs.open("test.json");
	
	assert(ifs.is_open());
	
	Json::Reader reader;
	Json::Value root;
	
	if (!reader.parse(ifs,root,false))
	{
		std::cout<<"reader.parse() fail"<<std::endl;
		return -1;
	}
	
	std::string out = root["mmac"].asString();  
	std::cout << "mmac  " << out << std::endl; 
	out = root["wmac"].asString();  
	std::cout << "wmac  " << out << std::endl; 
		
	const Json::Value arrayObj = root["data"]; 
	for (int i=0; i<arrayObj.size(); i++)  
	{  
		out = arrayObj[i]["mac"].asString();  
		std::cout << "data-->mac  " << out << std::endl;  
			
		out = arrayObj[i]["rssi"].asString();  
		std::cout << "data-->rssi  " << out << std::endl; 

		out = arrayObj[i]["tmc"].asString();  
		std::cout << "data-->tmc  " << out << std::endl; 
		
	}
	
	return 0; 
} 

（编辑：李大同）

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