jsoncpp的生成和使用

// TestJsoncppCode.cpp : Defines the entry point for the console application.
//

#include "stdafx.h"


#include "include/json/json.h"
#include <fstream>
#include <string>

#pragma comment(lib,"lib_json.lib")
using namespace std;

#ifdef _DEBUG
#define new DEBUG_NEW
#endif


// The one and only application object


void WriteJsonData(const char* filename)
{
	Json::Reader reader;
	Json::Value root; // Json::Value是一种很重要的类型，可以代表任意类型。如int,string,object,array...        

	std::ifstream is;
	is.open(filename,std::ios::binary);
	if (reader.parse(is,root))
	{
		Json::Value arrayObj;   // 构建对象  
		Json::Value new_item,new_item1;
		new_item["date"] = "2011-11-11";
		new_item1["time"] = "11:11:11";
		arrayObj.append(new_item);  // 插入数组成员  
		arrayObj.append(new_item1); // 插入数组成员  
		int file_size = root["files"].size();
		for (int i = 0; i < file_size; ++i)
			root["files"][i]["exifs"] = arrayObj;   // 插入原json中 
		std::string out = root.toStyledString();
		// 输出无格式json字符串  
		Json::FastWriter writer;
		std::string strWrite = writer.write(root);
		std::ofstream ofs;
		ofs.open("test_write.json");
		ofs << strWrite;
		ofs.close();
	}

	is.close();
}

int ReadJsonFromFile(const char* filename)
{
	Json::Reader reader;// 解析json用Json::Reader   
	Json::Value root; // Json::Value是一种很重要的类型，可以代表任意类型。如int,array...         

	std::ifstream is;
	is.open(filename,root,false))
	{
		std::string code;
		if (!root["files"].isNull())  // 访问节点，Access an object value by name,create a null member if it does not exist.  
			code = root["uploadid"].asString();

		code = root.get("uploadid","null").asString();// 访问节点，Return the member named key if it exist,defaultValue otherwise.    

		int file_size = root["files"].size();  // 得到"files"的数组个数  
		for (int i = 0; i < file_size; ++i)  // 遍历数组  
		{
			Json::Value val_image = root["files"][i]["images"];
			int image_size = val_image.size();
			for (int j = 0; j < image_size; ++j)
			{
				std::string type = val_image[j]["type"].asString();
				std::string url = val_image[j]["url"].asString();
				printf("type : %s,url : %s n",type.c_str(),url.c_str());
			}
		}
	}
	is.close();

	return 0;
}

int main(int argc,TCHAR* argv[],TCHAR* envp[])
{
	int nRetCode = 0;


	//1.从字符串解析json
	const char* str = "{"uploadid": "UP000000","code": 100,"msg": "","files": ""}";

	Json::Reader reader;
	Json::Value root;
	if (reader.parse(str,root))    // reader将Json字符串解析到root，root将包含Json里所有子元素  
	{
		printf("--------------从字符串读取JSON---------------n");
		std::string upload_id = root["uploadid"].asString();  // 访问节点，upload_id = "UP000000"  
		int code = root["code"].asInt();                      // 访问节点，code = 100 

		printf("upload_id : %sncode : %d n",upload_id.c_str(),code);
	}

	//2.从文件解析json
	string sTempPath = "test_json.json";

	printf("--------------从文件读取JSON---------------n");
	ReadJsonFromFile(sTempPath.c_str());


	//3.向文件写入json
	WriteJsonData(sTempPath.c_str());

	system("pause");

	return nRetCode;
}

（编辑：李大同）

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