数据结构_CJSON_对象解析_数据转换用途_1741859309.zip

# cJSON 的使用 ###### 简介 cJSON 是一个基于C语言的，可跨平台的解析字典、字符串组的数据结构。 ###### 下载地址 https://github.com/JHiroGuo/cJson 在cJSON中，json对象可以是json、字符串、数组等。 ###### 结构 ```C /* cJSON Types: */ #define cJSON_False 0 #define cJSON_True 1 #define cJSON_NULL 2 #define cJSON_Number 3 #define cJSON_String 4 #define cJSON_Array 5 #define cJSON_Object 6 #define cJSON_IsReference 256 /* The cJSON structure: */ typedef struct cJSON { struct cJSON *next,*prev; /* next/prev allow you to walk array/object chains. Alternatively, use GetArraySize/GetArrayItem/GetObjectItem */ struct cJSON *child; /* An array or object item will have a child pointer pointing to a chain of the items in the array/object. */ int type; /* The type of the item, as above. */ char *valuestring; /* The item's string, if type==cJSON_String */ int valueint; /* The item's number, if type==cJSON_Number */ double valuedouble; /* The item's number, if type==cJSON_Number */ char *string; /* The item's name string, if this item is the child of, or is in the list of subitems of an object. */ } cJSON; ``` ###### 解析Json ```C /* Supply a block of JSON, and this returns a cJSON object you can interrogate. Call cJSON_Delete when finished. */ extern cJSON *cJSON_Parse(const char *value); /* Render a cJSON entity to text for transfer/storage. Free the char* when finished. */ extern char *cJSON_Print(cJSON *item); /* Render a cJSON entity to text for transfer/storage without any formatting. Free the char* when finished. */ extern char *cJSON_PrintUnformatted(cJSON *item); /* Delete a cJSON entity and all subentities. */ extern void cJSON_Delete(cJSON *c); /* Returns the number of items in an array (or object). */ extern int cJSON_GetArraySize(cJSON *array); /* Retrieve item number "item" from array "array". Returns NULL if unsuccessful. */ extern cJSON *cJSON_GetArrayItem(cJSON *array,int item); /* Get item "string" from object. Case insensitive. */ extern cJSON *cJSON_GetObjectItem(cJSON *object,const char *string); /* For analysing failed parses. This returns a pointer to the parse error. You'll probably need to look a few chars back to make sense of it. Defined when cJSON_Parse() returns 0. 0 when cJSON_Parse() succeeds. */ extern const char *cJSON_GetErrorPtr(void); ``` ###### 解析Demo ```c++ { "semantic": { "slots": { "name": "张三" } }, "rc": 0, "operation": "CALL", "service": "telephone", "text": "打电话给张三" } ``` ```c #include <stdio.h> #include <stdlib.h> #include "cJSON.h" int main() { char * jsonStr = "{\"semantic\":{\"slots\":{\"name\":\"张三\"}}, \"rc\":0, \"operation\":\"CALL\", \"service\":\"telephone\", \"text\":\"打电话给张三\"}"; cJSON * root = NULL; cJSON * item = NULL;//cjson对象 root = cJSON_Parse(jsonStr); if (!root) { printf("Error before: [%s]\n",cJSON_GetErrorPtr()); } else { printf("%s\n", "有格式的方式打印Json:"); printf("%s\n\n", cJSON_Print(root)); printf("%s\n", "无格式方式打印json："); printf("%s\n\n", cJSON_PrintUnformatted(root)); printf("%s\n", "一步一步的获取name 键值对:"); printf("%s\n", "获取semantic下的cjson对象:"); item = cJSON_GetObjectItem(root, "semantic"); printf("%s\n", cJSON_Print(item)); printf("%s\n", "获取slots下的cjson对象"); item = cJSON_GetObjectItem(item, "slots"); printf("%s\n", cJSON_Print(item)); printf("%s\n", "获取name下的cjson对象"); item = cJSON_GetObjectItem(item, "name"); printf("%s\n", cJSON_Print(item)); printf("%s:", item->string); //打印Key printf("%s\n", item->valuestring);//打印Value } return 0; } ``` ###### 构造函数 ```C /* These calls create a cJSON item of the appropriate type. */ extern cJSON *cJSON_CreateNull(void); extern cJSON *cJSON_CreateTrue(void); extern cJSON *cJSON_CreateFalse(void); extern cJSON *cJSON_CreateBool(int b); extern cJSON *cJSON_CreateNumber(double num); extern cJSON *cJSON_CreateString(const char *string); extern cJSON *cJSON_CreateArray(void); extern cJSON *cJSON_CreateObject(void); /* These utilities create an Array of count items. */ extern cJSON *cJSON_CreateIntArray(const int *numbers,int count); extern cJSON *cJSON_CreateFloatArray(const float *numbers,int count); extern cJSON *cJSON_CreateDoubleArray(const double *numbers,int count); extern cJSON *cJSON_CreateStringArray(const char **strings,int count); ``` ###### 解析Demo ```C "semantic": { "slots": { "name": "张三" } }, "rc": 0, "operation": "CALL", "service": "telephone", "text": "打电话给张三" } #include <stdio.h> #include "cJSON.h" int main() { cJSON * root = cJSON_CreateObject(); cJSON * item = cJSON_CreateObject(); cJSON * next = cJSON_CreateObject(); cJSON_AddItemToObject(root, "rc", cJSON_CreateNumber(0));//根节点下添加 cJSON_AddItemToObject(root, "operation", cJSON_CreateString("CALL")); cJSON_AddItemToObject(root, "service", cJSON_CreateString("telephone")); cJSON_AddItemToObject(root, "text", cJSON_CreateString("打电话给张三")); cJSON_AddItemToObject(root, "semantic", item);//root节点下添加semantic节点 cJSON_AddItemToObject(item, "slots", next);//semantic节点下添加item节点 cJSON_AddItemToObject(next, "name", cJSON_CreateString("张三"));//添加name节点 printf("%s\n", cJSON_Print(root)); return 0; } ``` ###### 其他常用函数 ```c /* Update array items. */ extern void cJSON_ReplaceItemInArray(cJSON *array,int which,cJSON *newitem); extern void cJSON_ReplaceItemInObject(cJSON *object,const char *string,cJSON *newitem); /* Duplicate a cJSON item */ extern cJSON *cJSON_Duplicate(cJSON *item,int recurse); /* Duplicate will create a new, identical cJSON item to the one you pass, in new memory that will need to be released. With recurse!=0, it will duplicate any children connected to the item. The item->next and ->prev pointers are always zero on return from Duplicate. */ /* Delete a cJSON entity and all subentities. */ extern void cJSON_Delete(cJSON *c); ``` PS: cJSON 对象是指针类型 ，所以在创建之后一定要调用 cJSON_Delete 删除函数。 ```c #include <math.h> #include <stdio.h> #include <string.h> #include <stdlib.h> #include "cJSON.h" static void print_cjson_obj_value(const cJSON * obj) { if (!obj) { printf("NULL object!\n"); } switch (obj->type) { case cJSON_False: printf("%s: false\n", obj->string); break; case cJSON_True: printf("%s: true\n", obj->string); break; case cJSON_NULL: printf("%s: cJSON_NULL\n", obj->string); break; case cJSON_Number: printf("%s: %d, %f\n", obj->string, obj->valueint, obj->valuedouble); break; case cJSON_String: printf("%s: %s\n", obj->string, obj->valuestring); break; case cJSON_Array: printf("%s: cJSON_Array\n", obj->string); break; case cJSON_Object: printf("%s: cJSON_Object\n", obj->string); break; default: printf("unknown type\n"); } } /* * * 字符串转换成json对象 */ int test_parse_json_string_to_object() { #define MY_JSON_STRING \ "{\"name\": \"Jack (\\\"Bee\\\") Nimble\", \ \"format\": { \ \"type\": \"rect\", \ \"width\": 1920, \ \"interlace\": true, \ \"height\": 123.1 \ },