RapidJSON 介绍

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1. RapidJSON 介绍

RapidJSON 是一个解析和生成 JSON 的 C++ 库。
无需编译，包含头文件即可使用。

2. RapidJSON 使用

2.1 解析

@H_404_15@const char* json = "{" "\"stringValue\": \"hello world\"," "\"boolTrue\": true," "\"boolFalse\": false," "\"nullValue\": null," "\"intValue\": 3498," "\"floatValue\": 3.14," "\"arrayValue\": [1,2,3,4]" "}"; // parse json Document document; document.Parse(json); assert(document.IsObject());

2.2 查询

2.2.1 查询字符串

@H_404_15@// query string const char* STRING_VALUE = "stringValue"; assert(document.HasMember(STRING_VALUE)); assert(document[STRING_VALUE].IsString()); std::cout << STRING_VALUE << " = " << document[STRING_VALUE].GetString() << std::endl;

2.2.2 查询 Bool 值

@H_404_15@// query bool const char* BOOL_TRUE = "boolTrue"; assert(document.HasMember(BOOL_TRUE)); assert(document[BOOL_TRUE].IsBool()); assert(document[BOOL_TRUE].IsTrue()); std::cout << BOOL_TRUE << " = " << std::boolalpha << document[BOOL_TRUE].GetBool() << std::endl; const char* BOOL_FALSE = "boolFalse"; assert(document.HasMember(BOOL_FALSE)); assert(document[BOOL_FALSE].IsBool()); assert(document[BOOL_FALSE].IsFalse()); std::cout << BOOL_FALSE << " = " << std::boolalpha << document[BOOL_FALSE].GetBool() << std::endl;

2.2.3 判断是否为 Null 值

@H_404_15@// query null value const char* NULL_VALUE = "nullValue"; assert(document.HasMember(NULL_VALUE)); std::cout << NULL_VALUE << " = " << (document[NULL_VALUE].IsNull() ? "null" : "?") << std::endl;

2.2.4 查询 Int 值

@H_404_15@// query int value const char* INT_VALUE = "intValue"; assert(document.HasMember(INT_VALUE)); assert(document[INT_VALUE].IsNumber()); assert(document[INT_VALUE].IsInt()); assert(document[INT_VALUE].IsInt64()); assert(document[INT_VALUE].IsUint()); assert(document[INT_VALUE].IsUint64()); std::cout << INT_VALUE << "(int) = " << document[INT_VALUE].GetInt() << std::endl; std::cout << INT_VALUE << "(uint) = " << document[INT_VALUE].GetUint() << std::endl; std::cout << INT_VALUE << "(int64) = " << document[INT_VALUE].GetInt64() << std::endl; std::cout << INT_VALUE << "(uint64) = " << document[INT_VALUE].GetUint64() << std::endl;

2.2.5 查询 Float 值

@H_404_15@// query float value const char* FLOAT_VALUE = "floatValue"; assert(document.HasMember(FLOAT_VALUE)); assert(document[FLOAT_VALUE].IsNumber()); assert(document[FLOAT_VALUE].IsFloat()); assert(document[FLOAT_VALUE].IsDouble()); std::cout << FLOAT_VALUE << "(float) = " << document[FLOAT_VALUE].GetFloat() << std::endl; std::cout << FLOAT_VALUE << "(double) = " << document[FLOAT_VALUE].GetDouble() << std::endl;

2.2.6 查询数组

@H_404_15@// query array const char* ARRAY_VALUE = "arrayValue"; const Value& arrayValue = document[ARRAY_VALUE]; assert(arrayValue.IsArray()); for (SizeType i = 0; i != arrayValue.Size(); ++i) { assert(arrayValue[i].IsInt()); std::cout << ARRAY_VALUE << "[" << i << "] = " << arrayValue[i].GetInt() << std::endl; } for (Value::ConstValueIterator iter = arrayValue.Begin(); iter != arrayValue.End(); ++iter) { assert(iter->IsInt()); std::cout << iter->GetInt() << std::endl; } // Range-based For Loop,C++11 only for (auto& value : arrayValue.GetArray()) { assert(value.IsInt()); std::cout << value.GetInt() << std::endl; }

2.2.7 查询对象

@H_404_15@// query object static const char* kTypeNames[] = { "Null","False","True","Object","Array","String","Number" }; for (Value::ConstMemberIterator iter = document.MemberBegin(); iter != document.MemberEnd(); ++iter) { std::cout << "Type of member " << iter->name.GetString() << " is " << kTypeNames[iter->value.GetType()] << std::endl; } // Range-based For Loop,C++11 only for (auto& member : document.GetObject()) { std::cout << "Type of member " << member.name.GetString() << " is " << kTypeNames[member.value.GetType()] << std::endl; } // find member Value::ConstMemberIterator iter = document.FindMember(STRING_VALUE); if (iter != document.MemberEnd()) { std::cout << STRING_VALUE << " = " << iter->value.GetString() << std::endl; }

3.完整的例子

@H_404_15@#include "rapidjson/document.h" #include "rapidjson/stringbuffer.h" #include "rapidjson/writer.h" #include <iostream> #include <string> void testQuery() { using namespace rapidjson; const char* json = "{" "\"stringValue\": \"hello world\"," "\"boolTrue\": true," "\"boolFalse\": false," "\"nullValue\": null," "\"intValue\": 3498," "\"floatValue\": 3.14," "\"arrayValue\": [1,4]" "}"; // parse json Document document; document.Parse(json); assert(document.IsObject()); // query string const char* STRING_VALUE = "stringValue"; assert(document.HasMember(STRING_VALUE)); assert(document[STRING_VALUE].IsString()); std::cout << STRING_VALUE << " = " << document[STRING_VALUE].GetString() << std::endl; // query bool const char* BOOL_TRUE = "boolTrue"; assert(document.HasMember(BOOL_TRUE)); assert(document[BOOL_TRUE].IsBool()); assert(document[BOOL_TRUE].IsTrue()); std::cout << BOOL_TRUE << " = " << std::boolalpha << document[BOOL_TRUE].GetBool() << std::endl; const char* BOOL_FALSE = "boolFalse"; assert(document.HasMember(BOOL_FALSE)); assert(document[BOOL_FALSE].IsBool()); assert(document[BOOL_FALSE].IsFalse()); std::cout << BOOL_FALSE << " = " << std::boolalpha << document[BOOL_FALSE].GetBool() << std::endl; // query null value const char* NULL_VALUE = "nullValue"; assert(document.HasMember(NULL_VALUE)); std::cout << NULL_VALUE << " = " << (document[NULL_VALUE].IsNull() ? "null" : "?") << std::endl; // query int value const char* INT_VALUE = "intValue"; assert(document.HasMember(INT_VALUE)); assert(document[INT_VALUE].IsNumber()); assert(document[INT_VALUE].IsInt()); assert(document[INT_VALUE].IsInt64()); assert(document[INT_VALUE].IsUint()); assert(document[INT_VALUE].IsUint64()); std::cout << INT_VALUE << "(int) = " << document[INT_VALUE].GetInt() << std::endl; std::cout << INT_VALUE << "(uint) = " << document[INT_VALUE].GetUint() << std::endl; std::cout << INT_VALUE << "(int64) = " << document[INT_VALUE].GetInt64() << std::endl; std::cout << INT_VALUE << "(uint64) = " << document[INT_VALUE].GetUint64() << std::endl; // query float value const char* FLOAT_VALUE = "floatValue"; assert(document.HasMember(FLOAT_VALUE)); assert(document[FLOAT_VALUE].IsNumber()); assert(document[FLOAT_VALUE].IsFloat()); assert(document[FLOAT_VALUE].IsDouble()); std::cout << FLOAT_VALUE << "(float) = " << document[FLOAT_VALUE].GetFloat() << std::endl; std::cout << FLOAT_VALUE << "(double) = " << document[FLOAT_VALUE].GetDouble() << std::endl; // query array const char* ARRAY_VALUE = "arrayValue"; const Value& arrayValue = document[ARRAY_VALUE]; assert(arrayValue.IsArray()); for (SizeType i = 0; i != arrayValue.Size(); ++i) { assert(arrayValue[i].IsInt()); std::cout << ARRAY_VALUE << "[" << i << "] = " << arrayValue[i].GetInt() << std::endl; } for (Value::ConstValueIterator iter = arrayValue.Begin(); iter != arrayValue.End(); ++iter) { assert(iter->IsInt()); std::cout << iter->GetInt() << std::endl; } // Range-based For Loop,C++11 only for (auto& value : arrayValue.GetArray()) { assert(value.IsInt()); std::cout << value.GetInt() << std::endl; } // query object static const char* kTypeNames[] = { "Null",C++11 only for (auto& member : document.GetObject()) { std::cout << "Type of member " << member.name.GetString() << " is " << kTypeNames[member.value.GetType()] << std::endl; } // find member Value::ConstMemberIterator iter = document.FindMember(STRING_VALUE); if (iter != document.MemberEnd()) { std::cout << STRING_VALUE << " = " << iter->value.GetString() << std::endl; } } void test1() { // 解析json const char* json = "{\"project\":\"rapidjson\",\"stars\":10}"; rapidjson::Document d; d.Parse(json); // 获取值 rapidjson::Value& s = d["stars"]; std::cout << "stars: " << s.GetInt() << std::endl; // 设置值 s.SetInt(s.GetInt() + 1); // 获取json rapidjson::StringBuffer buffer; rapidjson::Writer<rapidjson::StringBuffer> writer(buffer); d.Accept(writer); std::cout << buffer.GetString() << std::endl; } void test2() { // 创建json rapidjson::Document document; rapidjson::Document::AllocatorType& allocator = document.GetAllocator(); rapidjson::Value root(rapidjson::kObjectType); root.AddMember("project","rapidjson",allocator); root.AddMember("stars",12,allocator); rapidjson::StringBuffer buffer; rapidjson::Writer<rapidjson::StringBuffer> writer(buffer); root.Accept(writer); std::string reststring = buffer.GetString(); std::cout << reststring << std::endl; } int main(void) { testQuery(); test1(); test2(); return 0; } 原文链接：https://www.f2er.com/json/289027.html

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