c++ 使用json的库

你看到的这个文章来自于http://www.cnblogs.com/ayanmw

cJSON官网是：http://sourceforge.net/projects/cjson/?source=recommended

 

最新版本是2013年的，与2009年的变化不是很大。

看了代码，觉得挺好，只是是C语言的，不够好。

就改良了一下，内存自己管理。使用std::string 

 

http://files.cnblogs.com/ayanmw/cJSON_cpp_myversion.zip

使用起来如下：

#include <stdio.h>#include <stdlib.h>#include "cJSON.h" #define PS(V) printf(#V"=%s\n",V);#define PI(V) printf(#V"=%d\n",V);#define PF(V) printf(#V"=%f\n",V);int main (int argc, const char * argv[]) {    AddStack(__FUNCTION__);        const char * myjson="{\"name\":\"value\",\"jsonobject\":{\"int\":5,\"true\":true,\"false\":false,\"null\":null},\"jsonarray\":[\"array1\",\"array2\",12,true,false,null,\"12\",-1.2]}";    cJSON * jsonroot =new cJSON();    if(0==jsonroot->cJSON_Parse(myjson))        printf("Error to cJSON_Parse :%s %x\n",jsonroot->cJSON_GetErrorPtr(),jsonroot->cJSON_GetErrorPtr());    else{        const char * out=jsonroot->cJSON_Print( ).c_str();        printf("myjson=%s\n",out);         PS(jsonroot->toString().c_str());        const char * value=jsonroot->cJSON_GetString( "name").c_str();        PS(value);                cJSON *jsonobject=jsonroot->cJSON_GetObjectItem( "jsonobject");        PS(jsonroot->cJSON_GetString("jsonobject").c_str());        PS(jsonobject->toString().c_str());                PS(jsonobject->cJSON_GetString("null").c_str());        PS(jsonobject->cJSON_GetString("int").c_str());        PS(jsonobject->cJSON_GetString("true").c_str());                         PI(jsonobject->cJSON_GetInt("int") );         PI(jsonobject->cJSON_GetBoolean("true"));         PI( jsonobject->cJSON_GetBoolean("false") );                 cJSON *jsonarray=jsonroot->cJSON_GetObjectItem("jsonarray");        PS(jsonroot->cJSON_GetString("jsonarray").c_str());        PS(jsonarray->toString().c_str());                PI( jsonroot->cJSON_GetArraySize( ) );        PI( jsonobject->cJSON_GetArraySize( ) );        PI(jsonarray->cJSON_GetArraySize( ));                cJSON *arrayitem=jsonarray->cJSON_GetArrayItem( 0);         PS(arrayitem->valuestring);    }    PS("END Mark");    delete jsonroot;    return 0;}

toString()可以轻松获取到json的内容信息。以上是解析的。

生成json可以看cJSON的test.c 文件。

#include <stdio.h>#include <stdlib.h>#include "cJSON.h"/* Parse text to JSON, then render back to text, and print! */void doit(char *text){    char *out;cJSON *json;        json=cJSON_Parse(text);    if (!json) {printf("Error before: [%s]\n",cJSON_GetErrorPtr());}    else    {        out=cJSON_Print(json);        cJSON_Delete(json);        printf("%s\n",out);        free(out);    }}/* Read a file, parse, render back, etc. */void dofile(char *filename){    FILE *f=fopen(filename,"rb");fseek(f,0,SEEK_END);long len=ftell(f);fseek(f,0,SEEK_SET);    char *data=(char*)malloc(len+1);fread(data,1,len,f);fclose(f);    doit(data);    free(data);}/* Used by some code below as an example datatype. */struct record {const char *precision;double lat,lon;const char *address,*city,*state,*zip,*country; };/* Create a bunch of objects as demonstration. */void create_objects(){    cJSON *root,*fmt,*img,*thm,*fld;char *out;int i;    /* declare a few. */    /* Here we construct some JSON standards, from the JSON site. */        /* Our "Video" datatype: */    root=cJSON_CreateObject();        cJSON_AddItemToObject(root, "name", cJSON_CreateString("Jack (\"Bee\") Nimble"));    cJSON_AddItemToObject(root, "format", fmt=cJSON_CreateObject());    cJSON_AddStringToObject(fmt,"type",        "rect");    cJSON_AddNumberToObject(fmt,"width",        1920);    cJSON_AddNumberToObject(fmt,"height",        1080);    cJSON_AddFalseToObject (fmt,"interlace");    cJSON_AddNumberToObject(fmt,"frame rate",    24);        out=cJSON_Print(root);    cJSON_Delete(root);    printf("%s\n",out);    free(out);    /* Print to text, Delete the cJSON, print it, release the string. */    /* Our "days of the week" array: */    const char *strings[7]={"Sunday","Monday","Tuesday","Wednesday","Thursday","Friday","Saturday"};    root=cJSON_CreateStringArray(strings,7);    out=cJSON_Print(root);    cJSON_Delete(root);    printf("%s\n",out);    free(out);    /* Our matrix: */    int numbers[3][3]={{0,-1,0},{1,0,0},{0,0,1}};    root=cJSON_CreateArray();    for (i=0;i<3;i++) cJSON_AddItemToArray(root,cJSON_CreateIntArray(numbers[i],3));/*    cJSON_ReplaceItemInArray(root,1,cJSON_CreateString("Replacement")); */        out=cJSON_Print(root);    cJSON_Delete(root);    printf("%s\n",out);    free(out);    /* Our "gallery" item: */    int ids[4]={116,943,234,38793};    root=cJSON_CreateObject();    cJSON_AddItemToObject(root, "Image", img=cJSON_CreateObject());    cJSON_AddNumberToObject(img,"Width",800);    cJSON_AddNumberToObject(img,"Height",600);    cJSON_AddStringToObject(img,"Title","View from 15th Floor");    cJSON_AddItemToObject(img, "Thumbnail", thm=cJSON_CreateObject());    cJSON_AddStringToObject(thm, "Url", "http:/*www.example.com/image/481989943");    cJSON_AddNumberToObject(thm,"Height",125);    cJSON_AddStringToObject(thm,"Width","100");    cJSON_AddItemToObject(img,"IDs", cJSON_CreateIntArray(ids,4));    out=cJSON_Print(root);    cJSON_Delete(root);    printf("%s\n",out);    free(out);    /* Our array of "records": */    struct record fields[2]={        {"zip",37.7668,-1.223959e+2,"","SAN FRANCISCO","CA","94107","US"},        {"zip",37.371991,-1.22026e+2,"","SUNNYVALE","CA","94085","US"}};    root=cJSON_CreateArray();    for (i=0;i<2;i++)    {        cJSON_AddItemToArray(root,fld=cJSON_CreateObject());        cJSON_AddStringToObject(fld, "precision", fields[i].precision);        cJSON_AddNumberToObject(fld, "Latitude", fields[i].lat);        cJSON_AddNumberToObject(fld, "Longitude", fields[i].lon);        cJSON_AddStringToObject(fld, "Address", fields[i].address);        cJSON_AddStringToObject(fld, "City", fields[i].city);        cJSON_AddStringToObject(fld, "State", fields[i].state);        cJSON_AddStringToObject(fld, "Zip", fields[i].zip);        cJSON_AddStringToObject(fld, "Country", fields[i].country);    }    /*    cJSON_ReplaceItemInObject(cJSON_GetArrayItem(root,1),"City",cJSON_CreateIntArray(ids,4)); */        out=cJSON_Print(root);    cJSON_Delete(root);    printf("%s\n",out);    free(out);}int main (int argc, const char * argv[]) {    /* a bunch of json: */    char text1[]="{\n\"name\": \"Jack (\\\"Bee\\\") Nimble\", \n\"format\": {\"type\":       \"rect\", \n\"width\":      1920, \n\"height\":     1080, \n\"interlace\":  false,\"frame rate\": 24\n}\n}";        char text2[]="[\"Sunday\", \"Monday\", \"Tuesday\", \"Wednesday\", \"Thursday\", \"Friday\", \"Saturday\"]";    char text3[]="[\n    [0, -1, 0],\n    [1, 0, 0],\n    [0, 0, 1]\n    ]\n";    char text4[]="{\n        \"Image\": {\n            \"Width\":  800,\n            \"Height\": 600,\n            \"Title\":  \"View from 15th Floor\",\n            \"Thumbnail\": {\n                \"Url\":    \"http:/*www.example.com/image/481989943\",\n                \"Height\": 125,\n                \"Width\":  \"100\"\n            },\n            \"IDs\": [116, 943, 234, 38793]\n        }\n    }";    char text5[]="[\n     {\n     \"precision\": \"zip\",\n     \"Latitude\":  37.7668,\n     \"Longitude\": -122.3959,\n     \"Address\":   \"\",\n     \"City\":      \"SAN FRANCISCO\",\n     \"State\":     \"CA\",\n     \"Zip\":       \"94107\",\n     \"Country\":   \"US\"\n     },\n     {\n     \"precision\": \"zip\",\n     \"Latitude\":  37.371991,\n     \"Longitude\": -122.026020,\n     \"Address\":   \"\",\n     \"City\":      \"SUNNYVALE\",\n     \"State\":     \"CA\",\n     \"Zip\":       \"94085\",\n     \"Country\":   \"US\"\n     }\n     ]";    /* Process each json textblock by parsing, then rebuilding: */    doit(text1);    doit(text2);        doit(text3);    doit(text4);    doit(text5);    /* Parse standard testfiles: *//*    dofile("../../tests/test1"); *//*    dofile("../../tests/test2"); *//*    dofile("../../tests/test3"); *//*    dofile("../../tests/test4"); *//*    dofile("../../tests/test5"); */    /* Now some samplecode for building objects concisely: */    create_objects();        return 0;}

感觉比jsoncpp 代码简洁。算法看起来都是简单精炼的。很好的。