目录
还是从最基础开始、什么是JSON
一、只解析json
1..解析JSON的主要类
2.主函数
二、解析并利用结构体存储
1.定义结构体
2.从 JSON 解析并填充结构体
实战示例
还是从最基础开始、什么是JSON
JSON(JavaScript Object Notation)是一种轻量级的数据交换格式,它基于ECMAScript的一个子集,采用完全独立于语言的文本格式来存储和表示数据。简洁和清晰的层次结构使得JSON成为理想的数据交换语言。
JSON 的基本结构包括两种:
对象(在 JavaScript 中用花括号 {}
表示)
一个对象由一对大括号 {}
包围,对象内的属性是键值对的形式,键(key)和值(value)之间用冒号 :
分隔,多个键值对之间用逗号 ,
分隔。
示例
{ "name": "John", "age": 30, "city": "New York" }
数组(在 JavaScript 中用方括号 []
表示)
一个数组由一对方括号 []
包围,数组中的元素可以是任意类型的值(包括对象或数组),多个元素之间用逗号 ,
分隔。
示例:
[ { "name": "John", "age": 30 }, { "name": "Jane", "age": 25 } ]
在 JSON 中,字符串必须使用双引号 ""
包围,不能使用单引号 ''
。对象的键(key)也必须是字符串,并且用双引号包围。
除了对象和数组,JSON 还支持以下数据类型:
- 字符串(string)
- 数字(number)
- 对象(object)
- 数组(array)
- 布尔值(true/false)
- null
注意:JSON 不支持 JavaScript 中的函数、日期对象等复杂类型。
一、只解析json
示例JSON
假设我们有一个JSON文件data.json
,内容如下:
{
"name": "John Doe",
"age": 30,
"address": {
"street": "1234 Elm Street",
"city": "Somewhere",
"zipcode": "12345"
},
"phones": [
{"type": "home", "number": "123-456-7890"},
{"type": "work", "number": "098-765-4321"}
]
}
1..解析JSON的主要类
#include <QCoreApplication>
#include <QFile>
#include <QJsonDocument>
#include <QJsonObject>
#include <QJsonArray>
#include <QJsonValue>
#include <QDebug>class JsonParser {
public:JsonParser(const QString& filePath) : filePath(filePath) {}void parse() {QFile file(filePath);if (!file.open(QIODevice::ReadOnly)) {qWarning() << "Could not open file" << filePath;return;}QByteArray data = file.readAll();QJsonDocument doc = QJsonDocument::fromJson(data);if (!doc.isObject()) {qWarning() << "Invalid JSON format";return;}QJsonObject rootObj = doc.object();parseObject(rootObj);}private:QString filePath;void parseObject(const QJsonObject& obj) {for (const QString& key : obj.keys()) {QJsonValue value = obj.value(key);if (value.isObject()) {qDebug() << "Object:" << key;parseObject(value.toObject());} else if (value.isArray()) {qDebug() << "Array:" << key;parseArray(value.toArray());} else {qDebug() << key << ":" << value.toVariant().toString();}}}void parseArray(const QJsonArray& arr) {for (const QJsonValue& value : arr) {if (value.isObject()) {parseObject(value.toObject());} else if (value.isArray()) {parseArray(value.toArray());} else {qDebug() << value.toVariant().toString();}}}
};
2.主函数
#include <QCoreApplication>
#include "jsonparser.h"int main(int argc, char *argv[]) {QCoreApplication a(argc, argv);QString filePath = "data.json"; // JSON文件路径JsonParser parser(filePath);parser.parse();return a.exec();
}
这样利用嵌套的方法,就可以遍历所有的JSON的节点,输出所有的值,当然这个时候没有办法存储,只是解析出来内容,如果想要通过一个结构体来存储解析出来的所有数据,并且结构体需要合适的话,就需要声明好正确的结构体。
二、解析并利用结构体存储
示例JSON
假设我们有以下 JSON 数据:
{
"name": "John Doe",
"age": 30,
"address": {
"street": "123 Main St",
"city": "Anytown",
"zip": "12345"
},
"phone_numbers": [
{"type": "home", "number": "555-555-5555"},
{"type": "work", "number": "555-555-5556"}
]
}
那么我们需要按照这个json格式来定义好结构体,用于存储解析出来的内容
1.定义结构体
#include <QString>
#include <QVector>struct PhoneNumber {QString type;QString number;
};struct Address {QString street;QString city;QString zip;
};struct Person {QString name;int age;Address address;QVector<PhoneNumber> phoneNumbers;
};
2.从 JSON 解析并填充结构体
#include <QJsonDocument>
#include <QJsonObject>
#include <QJsonArray>
#include <QFile>
#include <QDebug>bool parseJsonToPerson(const QString& jsonString, Person& person) {QJsonDocument doc = QJsonDocument::fromJson(jsonString.toUtf8());if (doc.isNull() || !doc.isObject()) {qWarning() << "Failed to parse JSON";return false;}QJsonObject obj = doc.object();person.name = obj["name"].toString();person.age = obj["age"].toInt();QJsonObject addressObj = obj["address"].toObject();person.address.street = addressObj["street"].toString();person.address.city = addressObj["city"].toString();person.address.zip = addressObj["zip"].toString();QJsonArray phoneArray = obj["phone_numbers"].toArray();for (const QJsonValue& val : phoneArray) {QJsonObject phoneObj = val.toObject();PhoneNumber phone;phone.type = phoneObj["type"].toString();phone.number = phoneObj["number"].toString();person.phoneNumbers.append(phone);}return true;
}int main() {QString jsonString = R"({"name": "John Doe","age": 30,"address": {"street": "123 Main St","city": "Anytown","zip": "12345"},"phone_numbers": [{"type": "home", "number": "555-555-5555"},{"type": "work", "number": "555-555-5556"}]})";Person person;if (parseJsonToPerson(jsonString, person)) {qDebug() << "Name:" << person.name;qDebug() << "Age:" << person.age;qDebug() << "Address:" << person.address.street << person.address.city << person.address.zip;for (const PhoneNumber& phone : person.phoneNumbers) {qDebug() << "Phone:" << phone.type << phone.number;}} else {qDebug() << "Failed to parse JSON.";}return 0;
}
之后的问题就是看JSON的复杂程度了,因为JSON所有的内容很少,解析也只有这么些,但是如果JSON串很复杂,比如数组嵌套节点嵌套数组等等,就需要按照上方的方法,像解锁一样一层一层的解开,只是需要读懂json,但绝不是难的。
实战示例
这里就举例一个结构体嵌套结构体来存储JSON的实战示例吧
结构体定义为
struct RefineNumericalValuesElems
{RefineNumericalValuesElems() {}QString RH; QString SNOW; QString WW;QString VV; QString UU100;QString CH;QString UU;QString SDEPTH;QString LSRAIN;QString TCC;QString VV10;QString HH;QString PS;QString DT;QString VIS;QString UU10;QString LCC; QString TT; QString RAIN; QString CRAIN;QString HCC;QString TT2;QString STT;QString MSLP;QString CAPE;QString SH;QString SSTT;QString WG3H10M;QString VV100; QString DEG0;QString VO; QString DO; void showInfo() const {qDebug() << "RH:" << RH;qDebug() << "SNOW:" << SNOW;qDebug() << "WW:" << WW;qDebug() << "VV:" << VV;qDebug() << "UU100:" << UU100;qDebug() << "CH:" << CH;qDebug() << "UU:" << UU;qDebug() << "SDEPTH:" << SDEPTH;qDebug() << "LSRAIN:" << LSRAIN;qDebug() << "TCC:" << TCC;qDebug() << "VV10:" << VV10;qDebug() << "HH:" << HH;qDebug() << "PS:" << PS;qDebug() << "DT:" << DT;qDebug() << "VIS:" << VIS;qDebug() << "UU10:" << UU10;qDebug() << "LCC:" << LCC;qDebug() << "TT:" << TT;qDebug() << "RAIN:" << RAIN;qDebug() << "CRAIN:" << CRAIN;qDebug() << "HCC:" << HCC;qDebug() << "TT2:" << TT2;qDebug() << "STT:" << STT;qDebug() << "MSLP:" << MSLP;qDebug() << "CAPE:" << CAPE;qDebug() << "SH:" << SH;qDebug() << "SSTT:" << SSTT;qDebug() << "WG3H10M:" << WG3H10M;qDebug() << "VV100:" << VV100;qDebug() << "DEG0:" << DEG0;qDebug() << "VO:" << VO;qDebug() << "DO:" << DO;}
};struct GroundMeteorologyElems {QString clo_cov_lm; QString clo_cov_low; QString clo_height_lom; QString td; QString rh; QString mslp; QString rain_1h; QString rain_3h; QString rain_6h; QString rain_12h;QString rain_24h; QString pressure; QString pressure_change_24h; QString pressure_change_3h; QString tt; QString temp_change_24h; QString temp_max_24h;QString temp_min_24h; QString vis_human; QString weather;QString wd_avg_10mi;QString wd_avg_2mi; QString ws_avg_10mi;QString ws_avg_2mi;void showInfo() const {qDebug() << "clo_cov_lm:" << clo_cov_lm;qDebug() << "clo_cov_low:" << clo_cov_low;qDebug() << "clo_height_lom:" << clo_height_lom;qDebug() << "td:" << td;qDebug() << "rh:" << rh;qDebug() << "mslp:" << mslp;qDebug() << "rain_1h:" << rain_1h;qDebug() << "rain_3h:" << rain_3h;qDebug() << "rain_6h:" << rain_6h;qDebug() << "rain_12h:" << rain_12h;qDebug() << "rain_24h:" << rain_24h;qDebug() << "pressure:" << pressure;qDebug() << "pressure_change_24h:" << pressure_change_24h;qDebug() << "pressure_change_3h:" << pressure_change_3h;qDebug() << "tt:" << tt;qDebug() << "temp_change_24h:" << temp_change_24h;qDebug() << "temp_max_24h:" << temp_max_24h;qDebug() << "temp_min_24h:" << temp_min_24h;qDebug() << "vis_human:" << vis_human;qDebug() << "weather:" << weather;qDebug() << "wd_avg_10mi:" << wd_avg_10mi;qDebug() << "wd_avg_2mi:" << wd_avg_2mi;qDebug() << "ws_avg_10mi:" << ws_avg_10mi;qDebug() << "ws_avg_2mi:" << ws_avg_2mi;}
};struct WAFSForecastElems {QString CAT;QString CBE;QString CBTOP;void showInfo() const{qDebug() << "CAT:" << CAT;qDebug() << "CBE:" << CBE;qDebug() << "CBTOP:" << CBTOP;}
};struct Json_GROUND_METE_AREA{QString code;QString msg;struct Data {struct Values {QString station_id; QString name; QString lon; QString record_time; QString alti; QString lat;//要素组RefineNumericalValuesElems refineNumericalValuesElems;GroundMeteorologyElems groundMeteorologyElems;WAFSForecastElems wafsForecastElems;};QVector<Values> values;} data;void showInfo() const {qDebug() << "Json_GROUND_METE_AREA: \n";qDebug() << "Code:" << code;qDebug() << "Message:" << msg;for (const Data::Values &value : data.values) {qDebug() << "Values List:";qDebug() << "station_id:" << value.station_id;qDebug() << "name:" << value.name;qDebug() << "lon:" << value.lon;qDebug() << "record_time:" << value.record_time;qDebug() << "alti:" << value.alti;qDebug() << "lat:" << value.lat;value.refineNumericalValuesElems.showInfo();value.groundMeteorologyElems.showInfo();value.wafsForecastElems.showInfo();}}
};
解析函数
void Widget::parseRefineNumericalValuesElems(const QJsonObject &obj, RefineNumericalValuesElems &elems) {QMap<QString, QString*> map = {{"RH", &elems.RH},{"SNOW", &elems.SNOW},{"WW", &elems.WW},{"VV", &elems.VV},{"UU100", &elems.UU100},{"CH", &elems.CH},{"UU", &elems.UU},{"SDEPTH", &elems.SDEPTH},{"LSRAIN", &elems.LSRAIN},{"TCC", &elems.TCC},{"VV10", &elems.VV10},{"HH", &elems.HH},{"PS", &elems.PS},{"DT", &elems.DT},{"VIS", &elems.VIS},{"UU10", &elems.UU10},{"LCC", &elems.LCC},{"TT", &elems.TT},{"RAIN", &elems.RAIN},{"CRAIN", &elems.CRAIN},{"HCC", &elems.HCC},{"TT2", &elems.TT2},{"STT", &elems.STT},{"MSLP", &elems.MSLP},{"CAPE", &elems.CAPE},{"SH", &elems.SH},{"SSTT", &elems.SSTT},{"WG3H10M", &elems.WG3H10M},{"VV100", &elems.VV100},{"DEG0", &elems.DEG0},{"VO", &elems.VO},{"DO", &elems.DO}};for (auto it = map.begin(); it != map.end(); ++it) {if (obj.contains(it.key())) {*(it.value()) = obj[it.key()].toVariant().toString();}}
}void Widget::parseGroundMeteorologyElems(const QJsonObject &obj, GroundMeteorologyElems &elems)
{QMap<QString, QString*> map = {{"clo_cov_lm", &elems.clo_cov_lm},{"clo_cov_low", &elems.clo_cov_low},{"clo_height_lom", &elems.clo_height_lom},{"td", &elems.td},{"rh", &elems.rh},{"mslp", &elems.mslp},{"rain_1h", &elems.rain_1h},{"rain_3h", &elems.rain_3h},{"rain_6h", &elems.rain_6h},{"rain_12h", &elems.rain_12h},{"rain_24h", &elems.rain_24h},{"pressure", &elems.pressure},{"pressure_change_24h", &elems.pressure_change_24h},{"pressure_change_3h", &elems.pressure_change_3h},{"tt", &elems.tt},{"temp_change_24h", &elems.temp_change_24h},{"temp_max_24h", &elems.temp_max_24h},{"temp_min_24h", &elems.temp_min_24h},{"vis_human", &elems.vis_human},{"weather", &elems.weather},{"wd_avg_10mi", &elems.wd_avg_10mi},{"wd_avg_2mi", &elems.wd_avg_2mi},{"ws_avg_10mi", &elems.ws_avg_10mi},{"ws_avg_2mi", &elems.ws_avg_2mi}};for (auto it = map.begin(); it != map.end(); ++it) {if (obj.contains(it.key())) {*(it.value()) = obj[it.key()].toVariant().toString();}}
}void Widget::parseWAFSForecastElems(const QJsonObject &obj, WAFSForecastElems &elems)
{QMap<QString, QString*> map = {{"CAT", &elems.CAT},{"CBE", &elems.CBE},{"CBTOP", &elems.CBTOP}};for (auto it = map.begin(); it != map.end(); ++it) {if (obj.contains(it.key())) {*(it.value()) = obj[it.key()].toVariant().toString();}}
}Json_GLOBAL_REGIONAL_GROUND_METE Widget::parseGlobalRegionalGroundMeteData(const QByteArray &response)
{Json_GLOBAL_REGIONAL_GROUND_METE jsonToStructdata;QJsonDocument doc = QJsonDocument::fromJson(response);QJsonObject rootObj = doc.object();jsonToStructdata.code = rootObj["code"].toVariant().toString();jsonToStructdata.msg = rootObj["msg"].toVariant().toString();// 获取data对象QJsonObject dataObject = rootObj["data"].toObject();// 获取values字段
// QJsonObject valuesObject = dataObject["values"].toObject();QJsonArray valuesArray = dataObject.value("values").toArray();// 将values字段的数据填充到结构体中for (const QJsonValue &val : valuesArray) {QJsonObject valueObj = val.toObject();Json_GROUND_METE_AREA::Data::Values value;value.station_id = valueObj["station_id"].toVariant().toString();value.name = valueObj["name"].toVariant().toString();value.lon = valueObj["lon"].toVariant().toString();value.record_time = valueObj["record_time"].toVariant().toString();value.alti = valueObj["alti"].toVariant().toString();value.lat = valueObj["lat"].toVariant().toString();parseRefineNumericalValuesElems(valueObj, value.refineNumericalValuesElems);parseGroundMeteorologyElems(valueObj, value.groundMeteorologyElems);parseWAFSForecastElems(valueObj, value.wafsForecastElems);jsonToStructdata.data.values.append(value);}
// jsonToStructdata.showInfo();return jsonToStructdata;
}