c++实现Xml和json互转【转】

https://blog.csdn.net/kfy2011/article/details/51774242 

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;
}