qt解释json字符串的一个bug

作者：朱金灿

来源：http://blog.csdn.net/clever101

 

           

            最近使用qt(我用的是qt5.6)解析json字符串，发现qt的一个bug，代码如下：

#include 
#include 
#include 
#include 
#include 
#include 
#include
#include "json.h"

#if defined(_MSC_VER) && (_MSC_VER >= 1600)  
# pragma execution_character_set("utf-8")  
#endif

int QtJsonTest()
{
	QJsonParseError jsonError;
	QString qstrJson = "{\n  \"result\": true,\n  \"error\": \"\",\n  \"data\": {\n    \"User\": {\n      \"Uid\": 20556426650023957,\n      \"Username\": \"00B10C201D61\",\n      \"Password\": \"e10adc3949ba59abbe56e057f20f883e\",\n      \"Appid\": 9,\n      \"Sex\": \"\",\n      \"Email\": \"\",\n      \"GroupId\": 0,\n      \"ParentId\": 0,\n      \"Status\": \"\",\n      \"Registertime\": \"2017-11-10T10:35:38+08:00\",\n      \"Nikename\": \"\",\n      \"TelNumber\": \"\",\n      \"Lastlogintime\": \"2017-11-10T19:37:28.305962078+08:00\",\n      \"Role\": \"\",\n      \"Address\": \"\",\n      \"IconPath\": \"\",\n      \"ImagePath\": \"\",\n      \"Type\": 0,\n      \"Admin\": false,\n      \"Option\": \"\",\n      \"Terminals\": null\n    },\n    \"sessionid\": \"62719fc6cd0fc53a5dad5fed77ebfbd3\",\n    \"pushsessionid\": \"9_20556426650023957_4de289715bed48e21c919b48febd7ae2\"\n  }\n}";
	QJsonDocument json = QJsonDocument::fromJson(qstrJson.toUtf8(), &jsonError);
	if (jsonError.error == QJsonParseError::NoError)
	{
		if (json.isObject())
		{
			QJsonObject rootObj = json.object();

			if (rootObj.contains("data"))
			{
				QJsonValue data_value = rootObj.value(QString("data"));

				QJsonObject contentObj = data_value.toObject();

				if (contentObj.contains("User"))
				{
					QJsonValue user_value = contentObj.value(QString("User"));

					QJsonObject userObj = user_value.toObject();

					if (userObj.contains("Uid"))
					{
						QJsonValue UidValue = userObj.value("Uid");

						QJsonValue::Type type = UidValue.type();
						if (UidValue.isDouble())
						{
							double db = UidValue.toDouble();
							QString info("QT解析json字符串结果:");
							std::wcout << info.toStdWString()<< std::fixed << db << std::endl;

							return 0;
						}

					}
				}
			}
		}
	}
	return 1;
}

int JsoncppTest()
{
	QString qstrJson = "{\n  \"result\": true,\n  \"error\": \"\",\n  \"data\": {\n    \"User\": {\n      \"Uid\": 20556426650023957,\n      \"Username\": \"00B10C201D61\",\n      \"Password\": \"e10adc3949ba59abbe56e057f20f883e\",\n      \"Appid\": 9,\n      \"Sex\": \"\",\n      \"Email\": \"\",\n      \"GroupId\": 0,\n      \"ParentId\": 0,\n      \"Status\": \"\",\n      \"Registertime\": \"2017-11-10T10:35:38+08:00\",\n      \"Nikename\": \"\",\n      \"TelNumber\": \"\",\n      \"Lastlogintime\": \"2017-11-10T19:37:28.305962078+08:00\",\n      \"Role\": \"\",\n      \"Address\": \"\",\n      \"IconPath\": \"\",\n      \"ImagePath\": \"\",\n      \"Type\": 0,\n      \"Admin\": false,\n      \"Option\": \"\",\n      \"Terminals\": null\n    },\n    \"sessionid\": \"62719fc6cd0fc53a5dad5fed77ebfbd3\",\n    \"pushsessionid\": \"9_20556426650023957_4de289715bed48e21c919b48febd7ae2\"\n  }\n}";

	Json::Reader reader;
	Json::Value root;
	if (reader.parse(qstrJson.toStdString(), root))  // reader将Json字符串解析到root，root将包含Json里所有子元素   
	{
		qint64 uid = root["data"]["User"]["Uid"].asInt64();    // 访问节点
		QString info("Jsoncpp库解析json字符串结果:");
		std::wcout << info.toStdWString() << uid << std::endl;
		return 0;
	}
	else
	{
		return 1;
	}
	return 1;
}

int main(int argc, char *argv[])
{
	QCoreApplication a(argc, argv);

	setlocale(LC_CTYPE, "chs");

	QtJsonTest();

	JsoncppTest();

	getchar();
	return 1;
}

         

           代码编译环境为VS2013,Win7操作系统，unicode字符集，输出结果如下：

从上图可以看出jsoncpp的解析精度比qt5要高。通过查看qt源码也可以看出,qt对json类型的支持比较有限，仅支持以下类型：

    enum Type {
        Null =  0x0,
        Bool = 0x1,
        Double = 0x2,
        String = 0x3,
        Array = 0x4,
        Object = 0x5,
        Undefined = 0x80
    };

    jsoncpp支持json的类型比qt要多，具体是：

enum ValueType {
  nullValue = 0, ///< 'null' value
  intValue,      ///< signed integer value
  uintValue,     ///< unsigned integer value
  realValue,     ///< double value
  stringValue,   ///< UTF-8 string value
  booleanValue,  ///< bool value
  arrayValue,    ///< array value (ordered list)
  objectValue    ///< object value (collection of name/value pairs).
};