C++ rapidjson 使用

转JSON

rapidjson::Document document; document.SetObject(); ​ // 添加name, value const char* name = "success_url"; const char* value = "https://www.google.com"; document.AddMember(rapidjson::StringRef(name), rapidjson::StringRef(value), document.GetAllocator()); ​ // 添加json object rapidjson::Value info_objects(rapidjson::kObjectType); std::string jsonObject = "json_object"; info_objects.AddMember(rapidjson::StringRef("class_room"), rapidjson::StringRef("NO. 6110"), document.GetAllocator()); info_objects.AddMember(rapidjson::StringRef("teacher_name"), rapidjson::StringRef("ZhangSanfeng"), document.GetAllocator()); document.AddMember(rapidjson::StringRef(jsonObject.c_str()), info_objects, document.GetAllocator()); ​ // 添加json array rapidjson::Value array_objects(rapidjson::kArrayType); for (int i = 0; i < 2; i++) { Value object(kObjectType); Value nobject(kNumberType); nobject.SetInt(i); object.AddMember(StringRef("id"), nobject, document.GetAllocator()); object.AddMember(StringRef("name"), StringRef("zhangsan"), document.GetAllocator()); array_objects.PushBack(object, document.GetAllocator()); } char * jsonArrayName = "jsonArrayName"; document.AddMember(rapidjson::StringRef(jsonArrayName), array_objects, document.GetAllocator()); ​ rapidjson::StringBuffer buffer; rapidjson::Writer<rapidjson::StringBuffer> writer(buffer); document.Accept(writer); std::string json = std::string(buffer.GetString()); LOGD("testAddMember = %s", json.c_str());

用法One: 简单修改json字符串

// 1. 把 JSON 解析至 DOM。 const char* json = "{\"project\":\"rapidjson\",\"stars\":10}"; Document d; d.Parse(json); // 2. 利用 DOM 作出修改。 Value& s = d["stars"]; s.SetInt(s.GetInt() + 1); // 3. 把 DOM 转换（stringify）成 JSON。 StringBuffer buffer; Writer<StringBuffer> writer(buffer); d.Accept(writer); // Output {"project":"rapidjson","stars":11} std::cout << buffer.GetString() << std::endl;

用法Two: 构造简单json

 StringBuffer s; Writer<StringBuffer> writer(s); writer.StartObject(); // Between StartObject()/EndObject(), writer.Key("hello"); // output a key, writer.String("world"); // follow by a value. writer.Key("t"); writer.Bool(true); writer.Key("f"); writer.Bool(false); writer.Key("n"); writer.Null(); writer.Key("i"); writer.Uint(123); writer.Key("pi"); writer.Double(3.1416); writer.Key("a"); writer.StartArray(); // Between StartArray()/EndArray(), for (unsigned i = 0; i < 4; i++) writer.Uint(i); // all values are elements of the array. writer.EndArray(); writer.EndObject(); // {"hello":"world","t":true,"f":false,"n":null,"i":123,"pi":3.1416,"a":[0,1,2,3]} std::cout << s.GetString() << std::endl;

原文链接：https://blog.csdn.net/u0/article/details/

解析复杂数据

{ "retType": 0, "s2c": { "basicQotList": [ { "security": { "market": 1, "code": "HSI2004" }, "isSuspended": false } } ] } }

获取basicQotList数组里面的security字段的market值

rapidjson::Document doc; doc.Parse(value.data()); if (!doc.HasParseError()) { if (doc.HasMember("retType") && doc["retType"].IsInt()) { if (doc["retType"].GetInt() == 0) { if (doc.HasMember("s2c") && doc["s2c"].IsObject()) { rapidjson::Value& s2c_object = doc["s2c"]; if (s2c_object.HasMember("basicQotList") && s2c_object["basicQotList"].IsArray()) { auto rsp_ = s2c_object["basicQotList"].GetArray(); for (size_t i = 0; i < rsp_.Size(); i++) // 遍历列表行情数据 { rapidjson::Value& v = rsp_[i]; // 转换市场编号信息 std::string key_ = ""; if (v.HasMember("security") && v["security"].IsObject()) { int market_ = v["security"]["market"].GetInt(); std::string code_ = v["security"]["code"].GetString(); std::string market_str = getMarketStr(market_); if (market_str == "Unknown") { LG_ERROR("Unknown market."<< market_); continue; } key_ = market_str + "." + code_; } } ... } } } } }

获取字段是对象的字符串值

{ "account":"www", "data":{"message":"123","erorcode":0} }

获取data字段的字符串值：”{“message”:”123″,”erorcode”:0}”

rapidjson::Document doc; doc.Parse(json.data()); if (!doc.HasParseError()) { if (doc.HasMember("Data") && doc["Data"].IsObject()) { rapidjson::StringBuffer sb; rapidjson::Writer<rapidjson::StringBuffer> writer(sb); doc["Data"].Accept(writer); std::string Data_ = sb.GetString(); } }

注意：

有一个小坑是在用 AddMember方法添加成员时。可以发现AddMember有7个重载类型。

GenericValue& AddMember(GenericValue& name, GenericValue& value, Allocator& allocator)

而第一个参数name,只有两种：StringRefType和GenericValue< Encoding, Allocator >

官方文档对于StringRefType的解释是：Reference to a constant string （引用的常量字符串）

所以若通过要传递的key是用户键入的变量，需要转成Value类型

即：

 Value robot_key(YD_Robot.toStdString().c_str(), allocator); //传递key变量

 docPtr.AddMember(robot_key, docCamera, allocator);

若传递固定的常量:

docPtr.AddMember(“xiaoming”, docCamera, allocator); 即可。