開源庫介紹:RapidJson @ 凱吉的異想世界

在現今的資訊科技發展，到處可見Json資料的處理。

今天凱吉介紹一款open source的c++類別庫rapid json。該類別庫提供高效，簡單易用的API讓開發人員迅速開發相關應用。

以下為一段Json文件:

{
"Int": 1234,
"Double": 75.0000001,
"String": "Hello World",
"Object": {
"name": "Max",
"age": 18
},
"IntArray": [
1,
2,
3
],
"DoubleArray": [
1.0,
2.0,
3.0
],
"StringArray": [
"1",
"10",
"100"
],
"MixedArray": [
"ggyy",
1234,
"ssss",
1.0021
],
"People": [
{
"name": "Larry",
"age": 38,
"sex": true
},
{
"name": "Karcher",
"age": 38,
"sex": true
},
{
"name": "Sam",
"age": 50,
"sex": true
}
]
}

一、Write Json Format :

#include "rapidjson/stringbuffer.h"
#include "rapidjson/writer.h"
#include <iostream>
#include <string>

using namespace std;

void Serialize_1()
{
rapidjson::StringBuffer strBuf;
rapidjson::Writer<rapidjson::StringBuffer> writer(strBuf);

writer.StartObject();

// 整數型別
writer.Key("Int");
writer.Int(1);

   // 浮點數型別
writer.Key("Double");
writer.Double(12.0000001);

   // 字串型別
writer.Key("String");
writer.String("This is a string");

   // 自訂義結構型別
writer.Key("Object");
writer.StartObject();
writer.Key("name");
writer.String("qq849635649");
writer.Key("age");
writer.Int(25);
writer.EndObject();

// 陣列型別 (Array type)
  // 整數陣列(int array)
writer.Key("IntArray");
writer.StartArray();
//顺序写入即可
writer.Int(10);
writer.Int(20);
writer.Int(30);
writer.EndArray();

  // 浮點數陣列 (Double array)
writer.Key("DoubleArray");
writer.StartArray();
for(int i = 1; i < 4; i++)
{
writer.Double(i * 1.0);
}
writer.EndArray();

   // 字串陣列 (string array)
writer.Key("StringArray");
writer.StartArray();
writer.String("one");
writer.String("two");
writer.String("three");
writer.EndArray();

  // 混和型陣列(an array with mixed data types)
writer.Key("MixedArray");
writer.StartArray();
writer.String("one");
writer.Int(50);
writer.Bool(false);
writer.Double(12.005);
writer.EndArray();

// 自訂義資料陣列(an array customize data)
writer.Key("People");
writer.StartArray();
for(int i = 0; i < 3; i++)
{
writer.StartObject();
writer.Key("name");
writer.String("qq849635649");
writer.Key("age");
writer.Int(i * 10);
writer.Key("sex");
writer.Bool((i % 2) == 0);
writer.EndObject();
}
writer.EndArray();

writer.EndObject();

string data = strBuf.GetString();
cout << data << endl;
}

二、讀取Json format:

#include "rapidjson/document.h"
#include "rapidjson/stringbuffer.h"
#include "rapidjson/writer.h"

string data =
"{\"Int\":1,"
"\"Double\":12.0000001,"
"\"String\":\"This is a string\","
"\"Object\":{\"name\":\"qq849635649\",\"age\":25},"
"\"IntArray\":[10,20,30],"
"\"DoubleArray\":[1.0,2.0,3.0],"
"\"StringArray\":[\"one\",\"two\",\"three\"],"
"\"MixedArray\":[\"one\",50,false,12.005],"
"\"People\":[{\"name\":\"qq849635649\",\"age\":0,\"sex\":true},"
"{\"name\":\"qq849635649\",\"age\":10,\"sex\":false},"
"{\"name\":\"qq849635649\",\"age\":20,\"sex\":true}]}";

void parse() {
// 建立 rapidjson 物件
rapidjson::Document doc;
// 首先進行parsing，没有錯誤才能進行各個字段的parsing
if(!doc.Parse(data.data()).HasParseError())
{
// parse 整數型別(int type)
if(doc.HasMember("Int") && doc["Int"].IsInt())
{
cout << "Int = " << doc["Int"].GetInt() << endl;
}

// parse 浮點數型別(float type)
if(doc.HasMember("Double") && doc["Double"].IsDouble())
{
cout << "Double = " << doc["Double"].GetDouble() << endl;
}
// parse 字串型別(string type)
if(doc.HasMember("String") && doc["String"].IsString())
{
cout << "String = " << doc["String"].GetString() << endl;
}
// parse 物件型別(object type)
if(doc.HasMember("Object") && doc["Object"].IsObject())
{
const rapidjson::Value& object = doc["Object"];
if(object.HasMember("name") && object["name"].IsString())
{
cout << "Object.name = " << object["name"].GetString() << endl;
}
if(object.HasMember("age") && object["age"].IsInt())
{
cout << "Object.age = " << object["age"].GetInt() << endl;
}
}
/

// 解析陣列(Array)類型

// 整數陣列( int array)
if(doc.HasMember("IntArray") && doc["IntArray"].IsArray())
{
// 将文字轉換為rapidjson::Value类型
const rapidjson::Value& array = doc["IntArray"];
// 取得陣列長度
size_t len = array.Size();
// 透過loop掃完所有元素，記得将元素轉換为int，即需要呼叫GetInt()
for(size_t i = 0; i < len; i++)
{
cout << "IntArray[" << i << "] = " << array[i].GetInt() << endl;
}
}
// double 陣列( double array)
if(doc.HasMember("DoubleArray") && doc["DoubleArray"].IsArray())
{
const rapidjson::Value& array = doc["DoubleArray"];
size_t len = array.Size();
for(size_t i = 0; i < len; i++)
{
//为防止类型不匹配，一般会添加类型校验
if(array[i].IsDouble())
{
cout << "DoubleArray[" << i << "] = " << array[i].GetDouble() << endl;
}
}
}
// 字串陣列(string array)
if(doc.HasMember("StringArray") && doc["StringArray"].IsArray())
{
const rapidjson::Value& array = doc["StringArray"];
size_t len = array.Size();
for(size_t i = 0; i < len; i++)
{
if(array[i].IsString())
{
cout << "StringArray[" << i << "] = " << array[i].GetString() << endl;
}
}
}
// array with mixed type
if(doc.HasMember("MixedArray") && doc["MixedArray"].IsArray())
{
const rapidjson::Value& array = doc["MixedArray"];
size_t len = array.Size();
for(size_t i = 0; i < len; i++)
{
// 為防止型態不匹配，做型別檢查
if(array[i].IsString())
{
cout << "MixedArray[" << i << "] = " << array[i].GetString() << endl;
}
else if(array[i].IsBool())
{
cout << "MixedArray[" << i << "] = " << array[i].GetBool() << endl;
}
else if(array[i].IsInt())
{
cout << "MixedArray[" << i << "] = " << array[i].GetInt() << endl;
}
else if(array[i].IsDouble())
{
cout << "MixedArray[" << i << "] = " << array[i].GetDouble() << endl;
}
}
}
// 結構數據陣列(Array with custom struct)
if(doc.HasMember("People") && doc["People"].IsArray())
{
const rapidjson::Value& array = doc["People"];
size_t len = array.Size();
for(size_t i = 0; i < len; i++)
{
const rapidjson::Value& object = array[i];
// 為防止型態不匹配，做型別檢查
if(object.IsObject())
{
cout << "ObjectArray[" << i << "]: ";
if(object.HasMember("name") && object["name"].IsString())
{
cout << "name=" << object["name"].GetString();
}
if(object.HasMember("age") && object["age"].IsInt())
{
cout << ", age=" << object["age"].GetInt();
}
if(object.HasMember("sex") && object["sex"].IsBool())
{
cout << ", sex=" << (object["sex"].GetBool() ? "Men" : "Female") << endl;
}
}
}
}
}
/**
* 最后注意：因为rapidjson不會做安全檢查。