1. JSON概述
JSON: JavaScript 对象表示法( JavaScript Object Notation) 。是一种轻量级的数据交换格式。 它基于ECMAScript的一个子集。许多编程语言都很容易找到JSON 解析器和 JSON 库。 JSON 文本格式在语法上与创建 JavaScript 对象的代码相同。不同语言的不同json库对json标准的支持不尽相同,为了能让尽可能多的json库都能正常解析和生成json,定义JSON的规范很重要,推荐一个JSON规范《JSON风格指南》。
2. 常用C&C++ JSON库
常用且知名度较高的C&C++的JSON库有cJSON、json-c、JsonCpp等,腾讯员工开源的一个RapidJSON以高性能著称。C&C++的JSON库比较见RapidJSON作者的比较nativejson-benchmark。
3. 非常简单易用的CJsonObject
CJsonObject是基于cJSON全新开发一个C++版的JSON库,CJsonObject的最大优势是轻量(只有4个文件,拷贝到自己代码里即可,无须编译成库,且跨平台和编译器)、简单好用,开发效率极高,对多层嵌套json的读取和生成使用非常简单(大部分json解析库如果要访问多层嵌套json的最里层非常麻烦)。我一直使用的json库是一个较老版本的cJSON,cJSON的好处是简单易用,而且只有两个文件,直接复制到自己的代码中就可以用。cJSON也有一个非常容易让初用者头痛的地方,一不小心就造成内存泄漏了。为此,我基于cJSON封装了一个C++版的CJsonObject,该库比cJSON更简单易用,且只要不是有意不释放内存就不会发生内存泄漏。用CJsonObject的好处在于完全不用文档,看完Demo马上就会用,不明白的看一下头文件就知道,所有函数都十分通俗易懂,最为关键的一点是解析JSON和生成JSON的编码效率非常高。当然,毕竟是经过cJSON封装而来,效率会略低于cJSON,cJSON不支持的CJsonObject也不支持。个人认为,既然已经选了json,那一点点的解析性能差异就不重要了,如果追求性能可以选protobuf。CJsonObject在我最近5年做过的8个项目中广泛应用。CJsonObject非常简单易用,且表现稳定,2018年5月我把它开源https://github.com/Bwar/CJsonObject,并将持续维护。
来看看CJsonObject是如何简单易用:
demo.cpp:
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#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;
}
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Demo执行结果:
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[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" ]
}
}
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再来看看头文件,一看就知道如何使用:
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/*******************************************************************************
* 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_ */
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如果觉得CJsonObject不错,别忘了给个star,谢谢。
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原文链接:https://www.cnblogs.com/bwar/p/9191479.html