qt解释json字符串的一个bug

亦凉 2022-06-06 14:12 154阅读 0赞

作者：朱金灿

来源：[http://blog.csdn.net/clever101][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 <QtCore/QCoreApplication>
    #include <QDomComment>
    #include <QJsonDocument>
    #include <QJsonObject>
    #include <QJsonArray>
    #include <iostream>
    #include<iomanip>
    #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：

![Center][]

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).
    };

[http_blog.csdn.net_clever101]: http://blog.csdn.net/clever101
[Center]: /images/20220606/03251d9d916a4882aaaf673ce679c29c.png