c++实现Xml和json互转

1、下载c语言的cJson库源码，库很小，只有两个文件cJSON.c和cJSON.h。下载地址：https://sourceforge.net/projects/cjson/

2、c++实现Xml和json互转

2.1、头文件

#include "XmlJsonTransfer.h"
//#include "cmsDebug.h"
#include "WebSocket/src/cJSON.h"

#include <stdlib.h>
#include <string.h>
#include <stdio.h>
#include <assert.h>
#include <time.h>
#include <iostream>
using namespace std;

2.2、xml转json

// 依赖cJSon，递归
/*
<doc><a a1="1" a2="2">123</a></doc> 转 {"doc": {"a": {"-a1": "1","-a2": "2","#text": "123"}}}
*/
string Xml2Json(string strXml)
{
string pNext = strXml;
cJSON * reJson = cJSON_CreateObject();
cJSON * jsonArray = cJSON_CreateArray();
string strArrayKey = "";
int nPos = 0;

while ((nPos = pNext.find("<")) >= 0)
{
// 获取第一个节点，如：<doc><a a1="1" a2="2">123</a></doc>
int nPosS = pNext.find("<");
int nPosE = pNext.find(">");
if (nPosS < 0 || nPosE < 0)
{
printf("key error!");
}

string strKey = pNext.substr(nPosS+1, nPosE-nPosS-1);
// 解释属性，如：<a a1="1" a2="2">
cJSON * jsonVal = NULL;
if ((nPos = strKey.find("=")) > 0)
{
jsonVal = cJSON_CreateObject();
int nPos = strKey.find(" ");
string temp = strKey.substr(nPos+1);
strKey = strKey.substr(0, nPos);
while((nPos = temp.find("=")) > 0)
{
int nPos1 = temp.find("=");
int nPos2 = temp.find("\" ", nPos1 + 1);

string strSubKey = temp.substr(0, nPos1);
string strSubVal = temp.substr(nPos1+1);
if (nPos2 > 0)
strSubVal = temp.substr(nPos1+1, nPos2-nPos1-1);

// 去除转义字符 \"
if ((int)(nPos = strSubVal.find("\"")) >= 0)
{
int nEnd = strSubVal.find("\\", nPos+1);
strSubVal = strSubVal.substr(nPos+1, nEnd-nPos-1);
}
cJSON_AddItemToObject(jsonVal, ("-" + strSubKey).c_str(), cJSON_CreateString(strSubVal.c_str()));

if (nPos2 < 0)
break;

temp = temp.substr(nPos2+2);
}
}

int nPosKeyE = pNext.find("</" + strKey + ">");
if (nPosKeyE < 0)
{
printf("key error!");
}
// 获取节点内容，如<a a1="1" a2="2">123</a> 或 123
string strVal = pNext.substr(nPosE+1, nPosKeyE-nPosE-1);
if ((nPos = strVal.find("<")) >= 0)
{
// 包含子节点，如<a a1="1" a2="2">123</a>
strVal = Xml2Json(strVal);

if (jsonVal)
{
if (strVal != "")
cJSON_AddItemToObject(jsonVal, "#text", cJSON_Parse(strVal.c_str()));
}
else
{
jsonVal = cJSON_Parse(strVal.c_str());
}
}
else
{
// 不包含子节点，如123
if (jsonVal)
{
if (strVal != "")
cJSON_AddItemToObject(jsonVal, "#text", cJSON_CreateString(strVal.c_str()));
}
else
{
jsonVal = cJSON_CreateString(strVal.c_str());
}
}

// 获取下一个节点
pNext = pNext.substr(nPosKeyE + strKey.size() + 3);

// 根据下一节点判断是否为数组
int nPosNext = pNext.find("<");
int nPosNextSame = pNext.find("<" + strKey + ">");
if (strArrayKey != "" || (nPosNext>=0 && nPosNextSame>=0 && nPosNext==nPosNextSame))
{
// 数组
cJSON_AddItemToArray(jsonArray, jsonVal);
strArrayKey = strKey;
}
else
{
// 非数组
cJSON_AddItemToObject(reJson, strKey.c_str(), jsonVal);
}
}

if (strArrayKey != "")
{
cJSON_AddItemToObject(reJson, strArrayKey.c_str(), jsonArray);
}

string strJson = cJSON_Print(reJson);

if(reJson)
{
cJSON_Delete(reJson);
reJson = NULL;
}

return strJson;
}

2.3、json转xml

// 依赖cJSon，递归
/*
{"doc": {"a": {"-a1": "1","-a2": "2","#text": "123"}}}  转 <doc><a a1="1" a2="2">123</a></doc>
*/
string Json2Xml(string strJson)
{
string strXml = "";
cJSON *root = cJSON_Parse(strJson.c_str());
if (!root)
{
printf("strJson error!");
return "";
}

cJSON *pNext = root->child;
if (!pNext)
{
return strJson;
}

int nPos = 0;
while (pNext)
{
string strChild = cJSON_Print(pNext);
string strVal = Json2Xml(strChild);

if (pNext->string != NULL)
{
string strKey = pNext->string;
if ((nPos=strKey.find("-")) == 0)
{
// 属性项
strXml.append(" ");
strXml.append(strKey.substr(1));
strXml.append("=");
strXml.append(strVal);

if (pNext->next == NULL)
strXml.append(">");
}
else if ((nPos=strKey.find("#")) == 0)
{
// 值
strXml.append(">");
strXml.append(strVal);
}
else if ((int)(strVal.find("=")) > 0 /*&& (int)(strVal.find("<")) < 0*/)
{
// 包含属性项的键值对
strXml.append("<" + strKey);
strXml.append(strVal);
strXml.append("</" + strKey + ">");
}
else
{
// 修正底层无键的值数组的键，如：把<JUAN_XJ_preKey>123</JUAN_XJ_preKey>中的JUAN_XJ_preKey修正
if ((int)strVal.find("JUAN_XJ_preKey") >= 0)
{
replace_all(strVal, "JUAN_XJ_preKey", strKey);
strXml.append(strVal);
}
else
{
strXml.append("<" + strKey + ">");
strXml.append(strVal);
strXml.append("</" + strKey + ">");
}
}
}
else
{
// 不包含键的值数组， 如：["123", "456"]，暂时转为<JUAN_XJ_preKey>123</JUAN_XJ_preKey>
string strPreKey = "JUAN_XJ_preKey";
strXml.append("<" + strPreKey + ">");
strXml.append(strVal);
strXml.append("</" + strPreKey + ">");
}

pNext = pNext->next;
}

return strXml;
}

2.4、辅助函数

// 替换字符串
string&  replace_all(string& str, const string& old_value, const string& new_value)
{
while(true)
{
string::size_type   pos(0);
if((pos=str.find(old_value)) != string::npos)
str.replace(pos,old_value.length(),new_value);
else
break;
}
return   str;
}