英文:
Extracting Key from nested array JSON using cJSON
问题
我需要从嵌套的数组JSON中提取关键信息。
嵌套的C JSON
{"SDCERR": 0, "InfoMsg": "", "count": 18,"connections": {"b59519e0-917d-4c29-b31a-81e1837bd43e": {"activated": 0, "id": "PEAP_GTC_NO_CA_CERT", "type": ""},"518b71d4-28ca-41c5-abb6-88245f0bf3fb": {"activated": 0, "id": "Manoj", "type": ""},"91988884-d524-43a2-b255-88817330fd8b": {"activated": 0, "id": "NaveedP", "type": ""},"26dfa985-cea3-4138-b03e-ab25f96e1dbb": {"activated": 0, "id": "PEAP_MSCHAPv2_NO_CA_CERT", "type": ""},"0d82d7d3-a00a-45e3-a42b-66b13afc03f5": {"activated": 0, "id": "PEAP_MSCHAPv2_CA_CERT", "type": ""},"1bb69f6c-d75e-44ad-a6ee-de7a5095b57e": {"activated": 0, "id": "EAP_TLS_NO_CA_CERT", "type": ""},"566d673a-b48b-4e82-aaa5-724c61ed54c0": {"activated": 0, "id": "nagaveni", "type": ""},"9f382a6d-8e3e-4a7e-88e3-33f0b885dcd0": {"activated": 0, "id": "EAP_TTLS_NO_CA_CERT", "type": ""},"8284b1b8-a268-4a99-88e4-fdf35f6badb0": {"activated": 0, "id": "PSK", "type": ""},"7af2a874-4042-47e5-8065-4ed499901968": {"activated": 0, "id": "EAP_TTLS_CA_CERT", "type": ""},"3e622df0-cbd4-4660-afdd-d7b813a2f130": {"activated": 0, "id": "MANOJ-5G", "type": ""},"bd89b41c-5688-3e79-8353-f7391d8e5ce9": {"activated": 0, "id": "br-slave-wlan0", "type": ""},"cb116408-6a95-42d0-add8-8b40bdd3b4cd": {"activated": 0, "id": "PEAP_GTC_CA_CERT", "type": ""},"a99477b4-2ccd-42dc-909d-2c913851be2a": {"activated": 0, "id": "nagaveni 1", "type": ""},"a33750a5-3623-49b4-b784-97d718acc959": {"activated": 0, "id": "find", "type": ""},"54e7567b-505a-4d29-ba36-533bd2cf25dd": {"activated": 0, "id": "PEAP_WPA3_CA-cert", "type": ""},"e5018996-4c3d-4caa-bd08-2dfc4424f520": {"activated": 0, "id": "wireless@telxsids.net", "type": ""},"aa616959-ba9f-4ad4-bf5e-4eab629c5d58": {"activated": 1, "id": "internal-usb0"}}}
在这里，我需要通过引用id来获取UUID的值。
例如：if(id == "PSK")
获取UUID: 8284b1b8-a268-4a99-88e4-fdf35f6badb0。
请帮我解析嵌套的cJSON。
使用cJSON * deviceData = cJSON_GetObjectItem(root,"connections");函数进行了尝试，但无法获取特定的字符串。
英文:
I need to extract key form nested Array JSON .
Nested C jOSN
{"SDCERR": 0, "InfoMsg": "", "count": 18,"connections": {"b59519e0-917d-4c29-b31a-81e1837bd43e": {"activated": 0, "id": "PEAP_GTC_NO_CA_CERT", "type": ""},"518b71d4-28ca-41c5-abb6-88245f0bf3fb": {"activated": 0, "id": "Manoj", "type": ""},"91988884-d524-43a2-b255-88817330fd8b": {"activated": 0, "id": "NaveedP", "type": ""},"26dfa985-cea3-4138-b03e-ab25f96e1dbb": {"activated": 0, "id": "PEAP_MSCHAPv2_NO_CA_CERT", "type": ""},"0d82d7d3-a00a-45e3-a42b-66b13afc03f5": {"activated": 0, "id": "PEAP_MSCHAPv2_CA_CERT", "type": ""},"1bb69f6c-d75e-44ad-a6ee-de7a5095b57e": {"activated": 0, "id": "EAP_TLS_NO_CA_CERT", "type": ""},"566d673a-b48b-4e82-aaa5-724c61ed54c0": {"activated": 0, "id": "nagaveni", "type": ""},"9f382a6d-8e3e-4a7e-88e3-33f0b885dcd0": {"activated": 0, "id": "EAP_TTLS_NO_CA_CERT", "type": ""},"8284b1b8-a268-4a99-88e4-fdf35f6badb0": {"activated": 0, "id": "PSK", "type": ""},"7af2a874-4042-47e5-8065-4ed499901968": {"activated": 0, "id": "EAP_TTLS_CA_CERT", "type": ""},"3e622df0-cbd4-4660-afdd-d7b813a2f130": {"activated": 0, "id": "MANOJ-5G", "type": ""},"bd89b41c-5688-3e79-8353-f7391d8e5ce9": {"activated": 0, "id": "br-slave-wlan0", "type": ""},"cb116408-6a95-42d0-add8-8b40bdd3b4cd": {"activated": 0, "id": "PEAP_GTC_CA_CERT", "type": ""},"a99477b4-2ccd-42dc-909d-2c913851be2a": {"activated": 0, "id": "nagaveni 1", "type": ""},"a33750a5-3623-49b4-b784-97d718acc959": {"activated": 0, "id": "find", "type": ""},"54e7567b-505a-4d29-ba36-533bd2cf25dd": {"activated": 0, "id": "PEAP_WPA3_CA-cert", "type": ""},"e5018996-4c3d-4caa-bd08-2dfc4424f520": {"activated": 0, "id": "wireless@telxsids.net", "type": ""},"aa616959-ba9f-4ad4-bf5e-4eab629c5d58": {"activated": 1, "id": "internal-usb0"}}}
Here, by refering id I need get the value of UUID
Example: if(id =="PSK")
get the UUID :8284b1b8-a268-4a99-88e4-fdf35f6badb0.
Please help me how parse the nested cJSON.
Using cJSON * deviceData = cJSON_GetObjectItem(root,"connections"); function I tried, but unable to get the particular string.
答案1
得分: 0
使用cJSON_ArrayForEach(element, array)宏来迭代数组或对象的元素并查找匹配项。对于对象，element中的cJSON指针的string成员是当前元素的名称。
示例程序：
#include <cjson/cJSON.h>#include <fcntl.h>#include <stdio.h>#include <stdlib.h>#include <string.h>#include <sys/stat.h>#include <unistd.h>// 用于将JSON文件解析为cJSON结构的实用函数cJSON *parse_json_file(const char *filename) {int fd = open(filename, O_RDONLY);if (fd < 0) {return NULL;}struct stat st;if (fstat(fd, &st) < 0) {perror("fstat");close(fd);return NULL;}char *buffer = malloc(st.st_size);if (!buffer) {close(fd);return NULL;}if (read(fd, buffer, st.st_size) != st.st_size) {// 读取不完整，将其视为错误处理perror("read");close(fd);free(buffer);return NULL;}close(fd);cJSON *cj = cJSON_ParseWithLength(buffer, st.st_size);free(buffer);return cj;}int main(int argc, char **argv) {if (argc != 3) {fprintf(stderr, "Usage: %s FILENAME ID\n", argv[0]);return EXIT_FAILURE;}cJSON *cj = parse_json_file(argv[1]);if (!cj) {fprintf(stderr, "无法读取和解析 '%s'。\n", argv[1]);return EXIT_FAILURE;}// 提取 .connections。注意：始终使用区分大小写版本的函数cJSON *connections = cJSON_GetObjectItemCaseSensitive(cj, "connections");if (!connections) {fputs("JSON没有connections关键字。\n", stderr);return EXIT_FAILURE;}if (!cJSON_IsObject(connections)) {fputs("JSON connections值不是对象\n", stderr);return EXIT_FAILURE;}// 迭代 .connections 对象的元素const char *id = argv[2];cJSON *conn;cJSON_ArrayForEach(conn, connections) {// 对于每个元素的值，查看它是否是具有匹配id字段的对象if (cJSON_IsObject(conn)) {cJSON *json_id = cJSON_GetObjectItemCaseSensitive(conn, "id");if (json_id && cJSON_IsString(json_id) &&strcmp(json_id->valuestring, id) == 0) {// conn->string 是当前元素的键printf("UUID: %s\n", conn->string);}}}cJSON_Delete(cj);return 0;}
用法：
$ gcc -g -O -Wall -Wextra example.c -lcjson$ ./a.out input.json PSKUUID: 8284b1b8-a268-4a99-88e4-fdf35f6badb0
英文:
Use the cJSON_ArrayForEach(element, array) macro to iterate over the elements of an array or object and look for a match. For objects, the element cJSON pointer's string member is the name of the current element.
Example program:
#include <cjson/cJSON.h>#include <fcntl.h>#include <stdio.h>#include <stdlib.h>#include <string.h>#include <sys/stat.h>#include <unistd.h>// Utility function to read a JSON file into a cJSON structcJSON *parse_json_file(const char *filename) {int fd = open(filename, O_RDONLY);if (fd < 0) {return NULL;}struct stat st;if (fstat(fd, &st) < 0) {perror("fstat");close(fd);return NULL;}char *buffer = malloc(st.st_size);if (!buffer) {close(fd);return NULL;}if (read(fd, buffer, st.st_size) != st.st_size) {// Incomplete read; treat as an errorperror("read");close(fd);free(buffer);return NULL;}close(fd);cJSON *cj = cJSON_ParseWithLength(buffer, st.st_size);free(buffer);return cj;}int main(int argc, char **argv) {if (argc != 3) {fprintf(stderr, "Usage: %s FILENAME ID\n", argv[0]);return EXIT_FAILURE;}cJSON *cj = parse_json_file(argv[1]);if (!cj) {fprintf(stderr, "Unable to read and parse '%s'.\n", argv[1]);return EXIT_FAILURE;}// Extract .connections. Note: Always use the CaseSensitive versions of functionscJSON *connections = cJSON_GetObjectItemCaseSensitive(cj, "connections");if (!connections) {fputs("JSON has no connections key.\n", stderr);return EXIT_FAILURE;}if (!cJSON_IsObject(connections)) {fputs("JSON connections value isn't an object\n", stderr);return EXIT_FAILURE;}// Iterate over the elements of the .connections objectconst char *id = argv[2];cJSON *conn;cJSON_ArrayForEach(conn, connections) {// For each element's value, see if it's object with a matching id fieldif (cJSON_IsObject(conn)) {cJSON *json_id = cJSON_GetObjectItemCaseSensitive(conn, "id");if (json_id && cJSON_IsString(json_id) &&strcmp(json_id->valuestring, id) == 0) {// conn->string is the key of the current elementprintf("UUID: %s\n", conn->string);}}}cJSON_Delete(cj);return 0;}
and usage:
$ gcc -g -O -Wall -Wextra example.c -lcjson$ ./a.out input.json PSKUUID: 8284b1b8-a268-4a99-88e4-fdf35f6badb0
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