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这篇文章主要介绍了基于C++怎么编写一个Json解析器的相关知识，内容详细易懂，操作简单快捷，具有一定借鉴价值，相信大家阅读完这篇基于C++怎么编写一个Json解析器文章都会有所收获，下面我们一起来看看吧。
#pragma once
#ifndef _JSON_SERIALIZE_
#define _JSON_SERIALIZE_
// #include "Util.h"
#include <fstream>
#include <string>
#include <vector>
#include <map>
// NAME_SPACE_START(Json)
enum JsonType {
None,
Number,
String,
Array,
Bool,
Null,
Object
};
class JNull {
public:
JNull() {}
~JNull() {}
};
template<typename T>
class JBaseObject {
public:
JBaseObject() {}
virtual ~JBaseObject() {}
virtual JBaseObject* clone() = 0;
};
template<typename T>
class JHolderObject :public JBaseObject<T> {
private:
public:
T value;
JHolderObject(const T& val) :value(val) {}
~JHolderObject() {}
JBaseObject<T>* clone() override;
};
template<typename ValueType>
class JObject {
private:
JBaseObject<ValueType>* _value = nullptr;
public:
JObject() {}
JObject(const ValueType& value);
JObject(const JObject& obj) :_value(obj._value->clone()) {}
~JObject();
JObject<ValueType>& operator=(const ValueType& value);
ValueType* Cast() {
JHolderObject<ValueType>* temp = dynamic_cast<JHolderObject<ValueType>*>(_value);
return temp ? &temp->value : NULL;
}
ValueType& RefCast() {
return (static_cast<JHolderObject<ValueType>*>(_value))->value;
}
};
template<typename T>
class JsonItemBase {
public:
JsonItemBase() {}
virtual ~JsonItemBase() {}
virtual void f() {}
};
template<typename T>
class JsonItem {
private:
// JObject<T> _value;
T _value;
public:
JsonItem() {}
JsonItem(const JsonItem&);
JsonItem(const JObject<T>& obj);
JsonItem(const T& obj);
~JsonItem() {};
T& GetItemRefValue() {
return this->_value;
}
T* GetItemLpValue() {
return &this->_value;
}
};
class JsonKey {
public:
JsonType _type{ JsonType::None };
std::wstring _key{ L"" };
JsonKey() {}
JsonKey(const JsonType& type, const std::wstring& key) :_type(type), _key(key) {}
bool operator<(const JsonKey&) const;
};
class JsonValue {
public:
void* _value{ nullptr };
size_t _size{ 0 };
JsonValue() {}
JsonValue(void* value, const int& size) :_value(value), _size(size) {}
};
class JsonSerialize {
using string = std::string;
private:
std::vector<std::pair<JsonKey, JsonValue>> content;
string _filePath;
public:
JsonSerialize() {}
JsonSerialize(const string filePath);
~JsonSerialize() {};
bool Load(const string filePath = "");
template<typename T>
JsonItem<T>* GetValueByKey(string key);
std::vector<std::pair<JsonKey, JsonValue>>& GetContent();
void printAll(int tab = 0);
private:
};
// NAME_SPACE_END()
#endif //!_JSON_SERIALIZE_#include "JsonSerialize.h"
// #include "Util.h"
#include <iostream>
#include <sstream>
#include <atomic>
#include <exception>
#include <fstream>
#include <ios>
#include <string>
#include <utility>
#include <vector>
#include <stack>
// NAME_SPACE_START(Json)
template<typename T>
JBaseObject<T>* JHolderObject<T>::clone() {
return new JHolderObject<T>(this->value);
}
// template<typename T>
// T& JHolderObject<T>::GetValue(){
// return value;
// }
template<typename ValueType>
JObject<ValueType>::JObject(const ValueType& value) {
_value = new JHolderObject<ValueType>(value);
}
template<typename ValueType>
JObject<ValueType>::~JObject() {
if (_value) delete _value;
}
template<typename ValueType>
JObject<ValueType>& JObject<ValueType>::operator=(const ValueType& value) {
if (_value) delete _value;
_value = new JHolderObject<ValueType>(value);
return *this;
}
// template<typename ValueType>
// ValueType* JObject<ValueType>::Cast(){
// JHolderObject<ValueType>* temp=dynamic_cast<JHolderObject<ValueType>*>(_value);
// return temp?&temp->GetValue():NULL;
// }
// template<typename ValueType>
// ValueType& JObject<ValueType>::RefCast(){
// return (dynamic_cast<JHolderObject<ValueType>&>(_value)).GetValue();
// }
// template<typename T>
// JsonItem<T>::JsonItem(const JObject<T>& value)
// :JsonItemBase<T>(){
// this->_value=value;
// }
template<typename T>
JsonItem<T>::JsonItem(const T& objList)
{
this->_value = objList;
}
// //获取值
// template<typename T>
// T& JsonItem<T>::GetItemRefValue(){
// return this->_value.RefCast();
// }
// template<typename T>
// T* JsonItem<T>::GetItemLpValue(){
// return this->_value.Cast();
// }
std::ifstream _file;
void OpenFile(const std::string filePath) {
_file.open(filePath, std::ios::in);
if (!_file.is_open()) return;
}
void CloseFile() {
_file.close();
}
bool JsonKey::operator<(const JsonKey& j_key) const {
return false;
}
JsonSerialize::JsonSerialize(const std::string filePath) {
this->_filePath = filePath;
}
bool isFirst = true;
bool isQuote = false;
bool isKey = true;
bool isObj = false;
bool isObjEnd = true;
bool isArrEnd = true;
JsonType curType = JsonType::Null;
size_t objListDeep = 0;
size_t arrDeep = 0;
std::wstring key = L"";
std::wstring value = L"";
std::stack<std::wstring> arrKey;
std::stack<JsonType> cer;
std::vector<std::pair<bool,JsonItem<std::vector<JsonValue>>*>> arrValueList; //false直接放到对象中 true 放到objList中
std::vector<std::pair<bool,JsonItem<JsonSerialize>*>> objList; //false直接放到对象中 true 放到arrValueList中
void freeAll() {
for (std::pair<bool, JsonItem<std::vector<JsonValue>>*> item : arrValueList)
if (item.second) delete item.second;
for (std::pair<bool, JsonItem<JsonSerialize>*> item : objList)
if (item.second) delete item.second;
}
std::string stows(std::wstring& ws)
{
std::string curLocale = setlocale(LC_ALL, NULL); // curLocale = "C";
setlocale(LC_ALL, "chs");
const wchar_t* _Source = ws.c_str();
size_t _Dsize = 2 * ws.size() + 1;
char* _Dest = new char[_Dsize];
memset(_Dest, 0, _Dsize);
wcstombs(_Dest, _Source, _Dsize);
std::string result = _Dest;
delete[]_Dest;
setlocale(LC_ALL, curLocale.c_str());
return result;
}
bool isBool(const std::wstring& str) {
return str == L"true";
}
bool isNumber(const std::wstring& str) {
std::wstring wstr = str;
std::stringstream ss(stows(wstr));
double d;
char c;
if (!(ss >> d)) return false;
if (ss >> c) return false;
return true;
}
bool Analysis(const char* buffer, std::vector<std::pair<JsonKey, JsonValue>>& content, const size_t length) {
size_t charLength = strlen(buffer) < length ? strlen(buffer) : length;
for (size_t i = 0; i < charLength; i++) {
char ch = buffer[i];
std::cout << ch;
if (ch == '{' && !isQuote) {
objListDeep++;
curType = JsonType::Object;
if (objListDeep >= 2) {
bool flag = (cer.empty() || cer.top() == JsonType::Object) ? false : true;
objList.push_back(std::pair<bool, JsonItem<JsonSerialize>*>(flag, new JsonItem<JsonSerialize>()));
isObj = true;
isObjEnd = false;
if (!isArrEnd) cer.push(JsonType::Array);
cer.push(JsonType::Object);
if (isKey) arrKey.push(L"");
}
}
else if (ch == '}' && !isQuote) {
if (objListDeep == 1 && isFirst == true) isFirst = false;
else if (objListDeep == 1 && isFirst == false) return false;
objListDeep--;
isObjEnd = true;
if (objListDeep != 0)
goto addArray;
}
else if (ch == '[' && !isQuote) {
bool flag = (cer.empty() || cer.top() == JsonType::Object) ? false : true;
curType = JsonType::Array;
arrDeep++;
arrValueList.push_back(std::pair<bool, JsonItem<std::vector<JsonValue>>*>(flag,new JsonItem<std::vector<JsonValue>>()));
isArrEnd = false;
if (!isObjEnd) cer.push(JsonType::Object);
cer.push(JsonType::Array);
}
else if (ch == ']' && !isQuote) {
arrDeep--;
if (arrDeep == 0) isArrEnd = true;
goto addArray;
}
else if (ch == ' ' && !isQuote) continue;
else if (ch == '"' && !isQuote) {
isQuote = true;
if (isKey) key += L"\"";
else value += L"\"";
}
else if (ch == '"' && isQuote) {
isQuote = false;
if (isKey) key += L"\"";
else value += L"\"";
}
else if (ch == ':' && !isQuote) isKey = false;
else if ((ch == ',' || ch == '\n') && !isQuote) {
if ((key == L"" && value == L"" && objList.size() == 0 && arrValueList.size() == 0)
|| (key == L"" && value == L"" && !isArrEnd)) continue;
addArray: std::wstring inputKey = key == L"" ? L"" : key.replace(0, 1, L"");
inputKey = inputKey == L"" ? L"" : inputKey.replace(inputKey.find_last_of(L"\""), 1, L"");
JsonKey j_key;
JsonValue j_value;
JsonType insertType = JsonType::Null;
j_key._key = inputKey;
if (value == L"true" || value == L"false") { //Bool
JsonItem<bool> *objList=new JsonItem<bool>(isBool(value));
size_t size = sizeof(objList);
j_value._value = objList;
j_value._size = 1;
j_key._type = JsonType::Bool;
}
else if (value.find(L"\"") == 0 && value.find_last_of(L"\"") == value.size() - 1) { //String
size_t n = value.size();
std::wstring* temp = new std::wstring(value.begin(), value.end());
JsonItem<std::wstring*> *objList=new JsonItem<std::wstring*>(temp);
j_value._value = objList;
j_value._size = n;
j_key._type = JsonType::String;
}
else if (isNumber(value)) { //Number
double result = 0;
std::stringstream ss(stows(value));
ss >> result;
JsonItem<double> *objList=new JsonItem<double>(result);
size_t size = sizeof(objList);
j_value._value = objList;
//memcpy_s(j_value._value, size, &objList, size);
j_value._size = 1;
j_key._type = JsonType::Number;
}
else if (arrValueList.size() != 0 && objList.size() != 0) {//Array Add or Object Add
if (!isObjEnd) {
arrKey.push(inputKey);
key = L"";
isKey = true;
continue;
}
cer.pop();
void* _val = curType == JsonType::Object ? (void*)objList.back().second : (void*)arrValueList.back().second;
size_t _si = curType == JsonType::Object ?
objList.back().second->GetItemRefValue().GetContent().size() :
arrValueList.back().second->GetItemLpValue()->size();
j_key._key = arrKey.top();
j_value._value = _val;
j_value._size = _si;
j_key._type = JsonType::Object;
if (curType == JsonType::Object) objList.pop_back();
else arrValueList.pop_back();
//接下来确认是放到obj 还是 arrvalue 通过cer栈顶元素判断
JsonType upType = cer.top();
arrKey.pop();
if (upType == JsonType::Object)
objList.back().second->GetItemLpValue()->GetContent().push_back(std::pair<JsonKey, JsonValue>(j_key, j_value));
else
arrValueList.back().second->GetItemLpValue()->push_back(j_value);
continue;
}
else if (objList.size() != 0) {//Object
if (!isObjEnd && isKey) {
arrKey.push(inputKey);
key = L"";
continue;
}
cer.pop();
j_key._key = arrKey.top();
arrKey.pop();
j_value._value = objList.back().second;
j_value._size = objList.back().second->GetItemRefValue().GetContent().size();
j_key._type = JsonType::Object;
objList.pop_back();
if (objList.size() != 0) {
objList.back().second->GetItemLpValue()->GetContent().push_back(std::pair<JsonKey, JsonValue>(j_key, j_value));
continue;
}
}
else if (arrValueList.size() != 0 && objList.size() == 0) {//Array
if (!isArrEnd) {
arrKey.push(inputKey);
key = L"";
isKey = true;
continue;
}
cer.pop();
j_key._key = arrKey.empty()?inputKey:arrKey.top();
if (!arrKey.empty()) arrKey.pop();
j_value._value = arrValueList.back().second;
j_value._size = arrValueList.back().second->GetItemLpValue()->size();
j_key._type = JsonType::Array;
arrValueList.pop_back();
if (arrValueList.size() != 0) {
arrValueList.back().second->GetItemLpValue()->push_back(j_value);
continue;
}
}
else if (value == L"") { //Null
JsonItem<JNull>* objList = new JsonItem<JNull>();
size_t size = sizeof(objList);
j_value._value = objList;
j_value._size = 0;
j_key._type = JsonType::Null;
}
std::pair<JsonKey, JsonValue> pair(j_key, j_value);
if (!isObjEnd) {
objList.back().second->GetItemRefValue().GetContent().push_back(pair);
}
else content.push_back(pair);
key = L"";
value = L"";
isKey = true;
if (objListDeep == 1 && isObj) isObj = false;
}
else {
if (isKey && isQuote) key += std::wstring(1, ch);
else if (isKey && !isQuote) return false;
else if (!isKey) value += std::wstring(1, ch);
}
if (objListDeep < 0 || arrDeep < 0) return false;
}
return true;
}
bool JsonSerialize::Load(const string filePath) {
try {
if (filePath != "") {
this->_filePath = filePath;
}
OpenFile(this->_filePath);
while (!_file.eof()) {
char buffer[0x4000] = "";
size_t length = sizeof(buffer) / sizeof(char);
_file.read(buffer, length);
if (!Analysis(buffer, content, length)) {
CloseFile();
return false;
}
}
CloseFile();
freeAll();
return objListDeep == 0 && arrDeep == 0;
}
catch (std::exception ex) {
throw ex;
}
}
std::vector<std::pair<JsonKey, JsonValue>>& JsonSerialize::GetContent() {
return this->content;
}
template<typename T>
JsonItem<T>* JsonSerialize::GetValueByKey(string key)
{
JsonItem<T>* temp_value = nullptr;
for (auto item : this->content) {
if (item.first._key == key) {
temp_value = (JsonItem<T>*)(item.second._value);
break;
}
}
return temp_value;
}
void coutTab(int count) {
while (count--) {
std::cout << '\t';
}
}
void JsonSerialize::printAll(int tab) {
auto res = this->content;
coutTab(tab);
std::cout << "{" << std::endl;
for (auto it = res.begin(); it != res.end(); it++) {
JsonKey temp_key = it->first;
if (temp_key._type == JsonType::Number) {
JsonItem<double>* temp_value = (JsonItem<double>*)(it->second._value);
coutTab(tab + 1);
std::wcout << temp_key._key << " : " << temp_value->GetItemRefValue() << std::endl;
}
else if (temp_key._type == JsonType::String) {
JsonItem<std::wstring*>* temp_value = (JsonItem<std::wstring*>*)(it->second._value);
coutTab(tab + 1);
std::wcout << temp_key._key << " : " << *temp_value->GetItemRefValue() << "" << std::endl;
}
else if (temp_key._type == JsonType::Null) {
JsonItem<JNull>* temp_value = (JsonItem<JNull>*)(it->second._value);
coutTab(tab + 1);
std::wcout << temp_key._key << " : " << "NULL" << std::endl;
}
else if (temp_key._type == JsonType::Bool) {
JsonItem<bool>* temp_value = (JsonItem<bool>*)(it->second._value);
coutTab(tab + 1);
std::wcout << temp_key._key << " : " << (temp_value->GetItemRefValue() ? "true" : "false") << std::endl;
}
else if (temp_key._type == JsonType::Object) {
JsonItem<JsonSerialize>* temp_value = (JsonItem<JsonSerialize>*)(it->second._value);
temp_value->GetItemRefValue().printAll(tab + 1);
}
else if (temp_key._type == JsonType::Array) {
JsonItem<std::vector<JsonValue>>* temp_value =
(JsonItem<std::vector<JsonValue>>*)(it->second._value);
coutTab(tab + 1);
std::wcout << temp_key._key << ":[" << std::endl;
for (auto item : temp_value->GetItemRefValue()) {
JsonItem<JsonSerialize>* tt_value = (JsonItem<JsonSerialize>*)(item._value);
tt_value->GetItemLpValue()->printAll(tab + 2);
}
coutTab(tab + 1);
std::cout << "]" << std::endl;
}
}
coutTab(tab);
std::cout << "}" << std::endl;
}
// NAME_SPACE_END()int main() {
JsonSerialize json("F:\\C++\\mySource\\example\\test.json");
json.Load();
json.printAll();
return 0;
}关于“基于C++怎么编写一个Json解析器”这篇文章的内容就介绍到这里，感谢各位的阅读！相信大家对“基于C++怎么编写一个Json解析器”知识都有一定的了解，大家如果还想学习更多知识，欢迎关注亿速云行业资讯频道。
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