目录

cJSON使用(一)
cJSON使用(二)

实战举例

上文学习了cJSON库的一些理论知识，接下来开始进行实战．

从一个json文件中读取并解析这个文件．

代码实现

资源文件内容res.json:

{
  "config_appl": "file",
  "version": "0.1.0",
  "resources": {
      "key_p": "NA",
      "key_n": "WO",
      "key_e": "local",
      "key_ze": "na",
      "key_le": "na",
      "key_name": "na",
      "key_type": "file",
      "key_ID": "na"
  }
}

test.c代码：

#include<stdio.h>
#include<stdlib.h>
#include<string.h>
#include"cJSON.h"

char* read_file(const char *filename) {
    FILE *file = NULL;
    long length = 0;
    char *content = NULL;
    size_t read_chars = 0;

    /* open in read binary mode */
    file = fopen(filename, "rb");
    if (file == NULL)
    {
        goto cleanup;
    }

    /* get the length */
    if (fseek(file, 0, SEEK_END) != 0)
    {
        goto cleanup;
    }
    length = ftell(file);
    if (length < 0)
    {
        goto cleanup;
    }
    if (fseek(file, 0, SEEK_SET) != 0)
    {
        goto cleanup;
    }

    /* allocate content buffer */
    content = (char*)malloc((size_t)length + sizeof(""));
    if (content == NULL)
    {
        goto cleanup;
    }

    /* read the file into memory */
    read_chars = fread(content, sizeof(char), (size_t)length, file);
    if ((long)read_chars != length)
    {
        free(content);
        content = NULL;
        goto cleanup;
    }
    content[read_chars] = '\0';


cleanup:
    if (file != NULL)
    {
        fclose(file);
    }

    return content;
}

int main()
{
    char *json_file;
    cJSON * json_tmp;
    cJSON * ch, *key_ch;
    int size;
    int kye_size;
    int i, j;
    //使用官网函数读取文件（test/common.c）
    json_file = read_file("res.json");
    //解析json
    json_tmp = cJSON_Parse(json_file);

    //获取当前key值数量
    size = cJSON_GetArraySize(json_tmp);
    printf("%d\n", size);

    //判断数据类型
    ch = json_tmp->child;
    for(i = 0; i < size; i++){
        printf("[num=%d] [type=%d]\n", i, ch->type);
        ch = ch->next;
    }


    //打印每一个key值
    ch = json_tmp->child;
    for(i = 0; i < size; i++){
        if(cJSON_IsObject(ch)){
            kye_size = cJSON_GetArraySize(ch);
            key_ch = ch->child;
            printf("[num=%d          ]\n", i);
            printf("[key=%s]\n", ch->string);
            printf("----------------------\n");
            for(j = 0; j < kye_size; j++){
                printf("[value_num=%d          ]\n", j);
                printf("[key=%s]\n[value=%s]\n", key_ch->string, key_ch->valuestring); 
                key_ch = key_ch->next;
            }
            printf("----------------------\n");

        }else{
            printf("[num=%d          ]\n", i);
            printf("[key=%s]\n[value=%s]\n", ch->string, ch->valuestring);
        }
        ch = ch->next;
    }
}

编译执行命令：

gcc test.c cJSON.c -lm

运行结果：

image.png

参考

C - CJSON
CJSON 使用介绍
C语言cJSON库的使用，解析json数据格式