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C++JSON庫CJsonObject詳解(輕量簡單好用)

更新時(shí)間：2021年04月27日 14:32:27 作者：鐵芒箕

CJsonObject是基于cJSON全新開發(fā)一個(gè)C++版的JSON庫,CJsonObject的最大優(yōu)勢(shì)是輕量簡單好用，開發(fā)效率極高，對(duì)多層嵌套json的讀取和生成使用非常簡單,喜歡的朋友一起看看吧

1. JSON概述

JSON： JavaScript 對(duì)象表示法（ JavaScript Object Notation）。是一種輕量級(jí)的數(shù)據(jù)交換格式。它基于ECMAScript的一個(gè)子集。許多編程語言都很容易找到JSON 解析器和 JSON 庫。 JSON 文本格式在語法上與創(chuàng)建 JavaScript 對(duì)象的代碼相同。不同語言的不同json庫對(duì)json標(biāo)準(zhǔn)的支持不盡相同，為了能讓盡可能多的json庫都能正常解析和生成json，定義JSON的規(guī)范很重要，推薦一個(gè)JSON規(guī)范《JSON風(fēng)格指南》。

2. 常用C&C++ JSON庫

常用且知名度較高的C&C++的JSON庫有cJSON、json-c、JsonCpp等，騰訊員工開源的一個(gè)RapidJSON以高性能著稱。C&C++的JSON庫比較見RapidJSON作者的比較nativejson-benchmark。

3. 非常簡單易用的CJsonObject

CJsonObject是基于cJSON全新開發(fā)一個(gè)C++版的JSON庫，CJsonObject的最大優(yōu)勢(shì)是輕量（只有4個(gè)文件，拷貝到自己代碼里即可，無須編譯成庫，且跨平臺(tái)和編譯器）、簡單好用，開發(fā)效率極高，對(duì)多層嵌套json的讀取和生成使用非常簡單（大部分json解析庫如果要訪問多層嵌套json的最里層非常麻煩）。我一直使用的json庫是一個(gè)較老版本的cJSON，cJSON的好處是簡單易用，而且只有兩個(gè)文件，直接復(fù)制到自己的代碼中就可以用。cJSON也有一個(gè)非常容易讓初用者頭痛的地方，一不小心就造成內(nèi)存泄漏了。為此，我基于cJSON封裝了一個(gè)C++版的CJsonObject，該庫比cJSON更簡單易用，且只要不是有意不釋放內(nèi)存就不會(huì)發(fā)生內(nèi)存泄漏。用CJsonObject的好處在于完全不用文檔，看完Demo馬上就會(huì)用，不明白的看一下頭文件就知道，所有函數(shù)都十分通俗易懂，最為關(guān)鍵的一點(diǎn)是解析JSON和生成JSON的編碼效率非常高。當(dāng)然，畢竟是經(jīng)過cJSON封裝而來，效率會(huì)略低于cJSON，cJSON不支持的CJsonObject也不支持。個(gè)人認(rèn)為，既然已經(jīng)選了json，那一點(diǎn)點(diǎn)的解析性能差異就不重要了，如果追求性能可以選protobuf。CJsonObject在我最近5年做過的8個(gè)項(xiàng)目中廣泛應(yīng)用。CJsonObject非常簡單易用，且表現(xiàn)穩(wěn)定，2018年5月我把它開源https://github.com/Bwar/CJsonObject，并將持續(xù)維護(hù)。

來看看CJsonObject是如何簡單易用：

demo.cpp：

#include <string>
#include <iostream>
#include "../CJsonObject.hpp"

int main()
{
    int iValue;
    std::string strValue;
    neb::CJsonObject oJson("{\"refresh_interval\":60,"
                        "\"dynamic_loading\":["
                            "{"
                                "\"so_path\":\"plugins/User.so\", \"load\":false, \"version\":1,"
                                "\"cmd\":["
                                     "{\"cmd\":2001, \"class\":\"neb::CmdUserLogin\"},"
                                     "{\"cmd\":2003, \"class\":\"neb::CmdUserLogout\"}"
                                "],"
                                "\"module\":["
                                     "{\"path\":\"im/user/login\", \"class\":\"neb::ModuleLogin\"},"
                                     "{\"path\":\"im/user/logout\", \"class\":\"neb::ModuleLogout\"}"
                                "]"
                             "},"
                             "{"
                             "\"so_path\":\"plugins/ChatMsg.so\", \"load\":false, \"version\":1,"
                                 "\"cmd\":["
                                      "{\"cmd\":2001, \"class\":\"neb::CmdChat\"}"
                                 "],"
                             "\"module\":[]"
                             "}"
                        "]"
                    "}");
     std::cout << oJson.ToString() << std::endl;
     std::cout << "-------------------------------------------------------------------" << std::endl;
     std::cout << oJson["dynamic_loading"][0]["cmd"][1]("class") << std::endl;
     oJson["dynamic_loading"][0]["cmd"][0].Get("cmd", iValue);
     std::cout << "iValue = " << iValue << std::endl;
     oJson["dynamic_loading"][0]["module"][0].Get("path", strValue);
     std::cout << "strValue = " << strValue << std::endl;
     std::cout << "-------------------------------------------------------------------" << std::endl;
     oJson.AddEmptySubObject("depend");
     oJson["depend"].Add("nebula", "https://github.com/Bwar/Nebula");
     oJson["depend"].AddEmptySubArray("bootstrap");
     oJson["depend"]["bootstrap"].Add("BEACON");
     oJson["depend"]["bootstrap"].Add("LOGIC");
     oJson["depend"]["bootstrap"].Add("LOGGER");
     oJson["depend"]["bootstrap"].Add("INTERFACE");
     oJson["depend"]["bootstrap"].Add("ACCESS");
     std::cout << oJson.ToString() << std::endl;
     std::cout << "-------------------------------------------------------------------" << std::endl;
     std::cout << oJson.ToFormattedString() << std::endl;
}

Demo執(zhí)行結(jié)果：

[bwar@nebula demo]$ ./CJsonObjectTest
{"refresh_interval":60,"dynamic_loading":[{"so_path":"plugins/User.so","load":false,"version":1,"cmd":[{"cmd":2001,"class":"neb::CmdUserLogin"},{"cmd":2003,"class":"neb::CmdUserLogout"}],"module":[{"path":"im/user/login","class":"neb::ModuleLogin"},{"path":"im/user/logout","class":"neb::ModuleLogout"}]},{"so_path":"plugins/ChatMsg.so","load":false,"version":1,"cmd":[{"cmd":2001,"class":"neb::CmdChat"}],"module":[]}]}
-------------------------------------------------------------------
neb::CmdUserLogout
iValue = 2001
strValue = im/user/login
-------------------------------------------------------------------
{"refresh_interval":60,"dynamic_loading":[{"so_path":"plugins/User.so","load":false,"version":1,"cmd":[{"cmd":2001,"class":"neb::CmdUserLogin"},{"cmd":2003,"class":"neb::CmdUserLogout"}],"module":[{"path":"im/user/login","class":"neb::ModuleLogin"},{"path":"im/user/logout","class":"neb::ModuleLogout"}]},{"so_path":"plugins/ChatMsg.so","load":false,"version":1,"cmd":[{"cmd":2001,"class":"neb::CmdChat"}],"module":[]}],"depend":{"nebula":"https://github.com/Bwar/Nebula","bootstrap":["BEACON","LOGIC","LOGGER","INTERFACE","ACCESS"]}}
-------------------------------------------------------------------
{
    "refresh_interval": 60,
    "dynamic_loading":  [{
            "so_path":  "plugins/User.so",
            "load": false,
            "version":  1,
            "cmd":  [{
                    "cmd":  2001,
                    "class":    "neb::CmdUserLogin"
                }, {
                    "cmd":  2003,
                    "class":    "neb::CmdUserLogout"
                }],
            "module":   [{
                    "path": "im/user/login",
                    "class":    "neb::ModuleLogin"
                }, {
                    "path": "im/user/logout",
                    "class":    "neb::ModuleLogout"
                }]
        }, {
            "so_path":  "plugins/ChatMsg.so",
            "load": false,
            "version":  1,
            "cmd":  [{
                    "cmd":  2001,
                    "class":    "neb::CmdChat"
                }],
            "module":   []
        }],
    "depend":   {
        "nebula":   "https://github.com/Bwar/Nebula",
        "bootstrap":    ["BEACON", "LOGIC", "LOGGER", "INTERFACE", "ACCESS"]
    }
}

再來看看頭文件，一看就知道如何使用：

/*******************************************************************************
 * Project:  neb
 * @file     CJsonObject.hpp
 * @brief    Json
 * @author   bwarliao
 * @date:    2014-7-16
 * @note
 * Modify history:
 ******************************************************************************/

#ifndef CJSONOBJECT_HPP_
#define CJSONOBJECT_HPP_

#include <stdio.h>
#include <stddef.h>
#include <malloc.h>
#include <errno.h>
#include <unistd.h>
#include <limits.h>
#include <math.h>
#include <float.h>
#include <string>
#include <map>
#include "cJSON.h"


namespace neb
{

class CJsonObject
{
public:     // method of ordinary json object or json array
    CJsonObject();
    CJsonObject(const std::string& strJson);
    CJsonObject(const CJsonObject* pJsonObject);
    CJsonObject(const CJsonObject& oJsonObject);
    virtual ~CJsonObject();

    CJsonObject& operator=(const CJsonObject& oJsonObject);
    bool operator==(const CJsonObject& oJsonObject) const;
    bool Parse(const std::string& strJson);
    void Clear();
    bool IsEmpty() const;
    bool IsArray() const;
    std::string ToString() const;
    std::string ToFormattedString() const;
    const std::string& GetErrMsg() const
    {
        return(m_strErrMsg);
    }

public:     // method of ordinary json object
    bool AddEmptySubObject(const std::string& strKey);
    bool AddEmptySubArray(const std::string& strKey);
    CJsonObject& operator[](const std::string& strKey);
    std::string operator()(const std::string& strKey) const;
    bool Get(const std::string& strKey, CJsonObject& oJsonObject) const;
    bool Get(const std::string& strKey, std::string& strValue) const;
    bool Get(const std::string& strKey, int32& iValue) const;
    bool Get(const std::string& strKey, uint32& uiValue) const;
    bool Get(const std::string& strKey, int64& llValue) const;
    bool Get(const std::string& strKey, uint64& ullValue) const;
    bool Get(const std::string& strKey, bool& bValue) const;
    bool Get(const std::string& strKey, float& fValue) const;
    bool Get(const std::string& strKey, double& dValue) const;
    bool Add(const std::string& strKey, const CJsonObject& oJsonObject);
    bool Add(const std::string& strKey, const std::string& strValue);
    bool Add(const std::string& strKey, int32 iValue);
    bool Add(const std::string& strKey, uint32 uiValue);
    bool Add(const std::string& strKey, int64 llValue);
    bool Add(const std::string& strKey, uint64 ullValue);
    bool Add(const std::string& strKey, bool bValue, bool bValueAgain);
    bool Add(const std::string& strKey, float fValue);
    bool Add(const std::string& strKey, double dValue);
    bool Delete(const std::string& strKey);
    bool Replace(const std::string& strKey, const CJsonObject& oJsonObject);
    bool Replace(const std::string& strKey, const std::string& strValue);
    bool Replace(const std::string& strKey, int32 iValue);
    bool Replace(const std::string& strKey, uint32 uiValue);
    bool Replace(const std::string& strKey, int64 llValue);
    bool Replace(const std::string& strKey, uint64 ullValue);
    bool Replace(const std::string& strKey, bool bValue, bool bValueAgain);
    bool Replace(const std::string& strKey, float fValue);
    bool Replace(const std::string& strKey, double dValue);

public:     // method of json array
    int GetArraySize();
    CJsonObject& operator[](unsigned int uiWhich);
    std::string operator()(unsigned int uiWhich) const;
    bool Get(int iWhich, CJsonObject& oJsonObject) const;
    bool Get(int iWhich, std::string& strValue) const;
    bool Get(int iWhich, int32& iValue) const;
    bool Get(int iWhich, uint32& uiValue) const;
    bool Get(int iWhich, int64& llValue) const;
    bool Get(int iWhich, uint64& ullValue) const;
    bool Get(int iWhich, bool& bValue) const;
    bool Get(int iWhich, float& fValue) const;
    bool Get(int iWhich, double& dValue) const;
    bool Add(const CJsonObject& oJsonObject);
    bool Add(const std::string& strValue);
    bool Add(int32 iValue);
    bool Add(uint32 uiValue);
    bool Add(int64 llValue);
    bool Add(uint64 ullValue);
    bool Add(int iAnywhere, bool bValue);
    bool Add(float fValue);
    bool Add(double dValue);
    bool AddAsFirst(const CJsonObject& oJsonObject);
    bool AddAsFirst(const std::string& strValue);
    bool AddAsFirst(int32 iValue);
    bool AddAsFirst(uint32 uiValue);
    bool AddAsFirst(int64 llValue);
    bool AddAsFirst(uint64 ullValue);
    bool AddAsFirst(int iAnywhere, bool bValue);
    bool AddAsFirst(float fValue);
    bool AddAsFirst(double dValue);
    bool Delete(int iWhich);
    bool Replace(int iWhich, const CJsonObject& oJsonObject);
    bool Replace(int iWhich, const std::string& strValue);
    bool Replace(int iWhich, int32 iValue);
    bool Replace(int iWhich, uint32 uiValue);
    bool Replace(int iWhich, int64 llValue);
    bool Replace(int iWhich, uint64 ullValue);
    bool Replace(int iWhich, bool bValue, bool bValueAgain);
    bool Replace(int iWhich, float fValue);
    bool Replace(int iWhich, double dValue);

private:
    CJsonObject(cJSON* pJsonData);

private:
    cJSON* m_pJsonData;
    cJSON* m_pExternJsonDataRef;
    std::string m_strErrMsg;
    std::map<unsigned int, CJsonObject*> m_mapJsonArrayRef;
    std::map<std::string, CJsonObject*> m_mapJsonObjectRef;
};

}

#endif /* CJSONHELPER_HPP_ */

如果覺得CJsonObject不錯(cuò)，別忘了給個(gè)star，謝謝。