Qt之JSON字符串的序列化和反序列化
一、简介
JSON 用于存储结构化的数据，存储的格式为：bool、double、string、array、object、null等6种格式。bool 值用“true/false”表示， double 支持双精度；string 代表字符串；array 数组是列表，用方括号“[]”表示；object 对象是“键值对”组合，并且都是字符串，不能包含重复的 key，用大括号“{}”表示。JSON中的每条都用逗号隔开。如下是一个示例：
{ "Time" : 10, "Win10" : true, "ComputerType" : "Lenovo", "Hardware" : { "CPU" : "3.0GHZ", "Processor" : "i7-9700F", "RAM" : "16GB" "Windows" : { "Version" : "Windows10", "VersionNumber" : "21H2", "InstallDate" : "2022/04/28" } "Software" : [ "Office", "Photoshop" ] "UserName" : { } }
以上是常见6种存储格式，且Qt中的JSON类可分为QJsonValue(封装JSON值)、QJsonArray(封装JSON数组)、QJsonObject(封装JSON对象)、QJsonDocument(封住JSON文档)、QJsonParseError(解析JSON时的错误)等类。
二、构建JSON对象
//构建复杂JSON字符串 QJsonObject winObject; winObject.insert("Version", "Windows10"); winObject.insert("VersionNumber", "21H2"); winObject.insert("InstallDate", "2022/04/28"); QJsonObject hardObject; hardObject.insert("CPU", "3.0GHZ"); hardObject.insert("Processor", "i7-9700F"); hardObject.insert("RAM", "16GB"); hardObject.insert("Windows", QJsonValue(winObject)); //构建JSON数组 QJsonArray jsonArray; jsonArray.append("Office"); jsonArray.append("Photoshop"); //构建JSON对象 QJsonObject object; object.insert("Time", 10); object.insert("Win10", true); object.insert("ComputerType", "Lenovo"); object.insert("UserName", QJsonObject()); //构建空json object.insert("Hardware", QJsonValue(hardObject)); object.insert("Software", QJsonValue(jsonArray)); QJsonDocument document; document.setObject(object); m_arrayJson = document.toJson(QJsonDocument::Compact);
三、解析JSON对象
QString array; QJsonParseError jsonError; QJsonDocument document = QJsonDocument::fromJson(m_arrayJson, &jsonError); if (!document.isNull() && (QJsonParseError::NoError == jsonError.error)) { //解析JSON对象 if (document.isObject()) { QJsonObject object = document.object(); if (object.contains("Time")) { QJsonValue value = object.take("Time"); if (value.isDouble()) { int nTime = value.toVariant().toInt(); array.append(QString("Time : %1; ").arg(nTime)); } } if (object.contains("Win10")) { QJsonValue value = object.take("Win10"); if (value.isBool()) { bool bWin10= value.toVariant().toBool(); array.append(QString("Win10 : %1; ").arg(bWin10)); } } if (object.contains("ComputerType")) { QJsonValue value = object.take("ComputerType"); if (value.isString()) { QString strType = value.toVariant().toString(); array.append(QString("ComputerType : %1; ").arg(strType)); } } //解析JSON数组 if (object.contains("Software")) { QJsonValue value = object.take("Software"); if (value.isArray()) { QJsonArray arrayJson = value.toArray(); for (int var = 0; var < arrayJson.size(); ++var) { value = arrayJson.at(var); if (value.isString()) { QString strOffice = value.toString(); if (var > 0) { array.append(QString("%1; ").arg(strOffice)); } else { array.append(QString("Software: %1, ").arg(strOffice)); } } } } } //解析复杂JSON字符串 if (object.contains("Hardware")) { QJsonValue hardValue = object.take("Hardware"); if (hardValue.isObject()) { QJsonObject harObject = hardValue.toObject(); if (harObject.contains("Windows")) { QJsonValue winValue = harObject.take("Windows"); if (winValue.isObject()) { QJsonObject winObject = winValue.toObject(); if (winObject.contains("Version")) { QJsonValue verJson = winObject.take("Version"); if (verJson.isString()) { QString strVer = verJson.toVariant().toString(); array.append(QString("Version : %1, ").arg(strVer)); } } } } if (harObject.contains("CPU")) { QJsonValue value = harObject.take("CPU"); if (value.isString()) { QString strCPU = value.toVariant().toString(); array.append(QString("CPU : %1").arg(strCPU)); } } } } } } m_editParse->setText(array);
结果如下图所示
四、JSON数组的解析
[ { "cid": "CN01", "city": "北京", "nation": "中国", }, { "cid": "US02", "city": "华盛顿", "nation:" "美国" }, ]
json数组示例一：
QJsonObject cn_json; cn_json.insert("cid", "CN01"); cn_json.insert("city", "beijing"); cn_json.insert("nation", "china"); QJsonObject us_json; us_json.insert("cid", "US02"); us_json.insert("city", "washington"); us_json.insert("nation", "us"); QJsonArray array; array.append(QJsonValue(cn_json)); array.append(QJsonValue(us_json)); QByteArray data = QJsonDocument(array).toJson(QJsonDocument::Compact);
json数组解析
QJsonParseError jsonError; QJsonDocument document = QJsonDocument::fromJson(data, &jsonError); if (jsonError.error == QJsonParseError::NoError) { QVariantList list = document.toVariant().toList(); foreach (QVariant variant, list) { qDebug() << "cid:" << variant.toMap()["cid"].toString(); qDebug() << "city:" << variant.toMap()["city"].toString(); qDebug() << "nation:" << variant.toMap()["nation"].toString(); } }
json数组示例二：
QJsonObject json_1; json_1.insert("id", "20230402221529"); QJsonObject json_2; json_2.insert("id", "20230402203158"); QJsonObject json_3; json_3.insert("id", "20230402175752"); QJsonArray array; array.append(QJsonValue(json_1)); array.append(QJsonValue(json_2)); array.append(QJsonValue(json_3)); QJsonObject json; json.insert("data", QJsonValue(array)); QByteArray data = QJsonDocument(json).toJson(QJsonDocument::Compact); qDebug() << "data:" << data;
json数组解析
QJsonParseError jsonError; QJsonDocument json_doc = QJsonDocument::fromJson(data, &jsonError); if (jsonError.error == QJsonParseError::NoError) { QJsonObject root_obj = json_doc.object(); if (root_obj.contains("data")) { QJsonValue json_value = root_obj.value("data"); if (json_value.isArray()) { QJsonArray array = json_value.toArray(); for (int i = 0; i < array.size(); ++i) { QJsonValue id_value = array.at(i); if (id_value.isObject()) { QJsonObject id_object = id_value.toObject(); qDebug() << "id:" << id_object.take("id").toVariant().toString(); //QString id = id_object["id"].toString(); //qDebug() << "id:" << id; } } } } }
