cJSON编程示例

1.程序源码

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <malloc.h>
#include <cjson.h>

/*计算文件大小*/
int file_size(char *filename)
{
        FILE *fp = fopen(filename,"r");
        int size = 0;

        if(!fp)
                return -1;

        fseek(fp,0L,SEEK_END);

        size = ftell(fp);

        fclose(fp);

        return size;
}

int read_all(char *src_file, char *buf, int size)
{
        FILE *fp = fopen(src_file,"r");
        int i = 0;

        if(fp < 0)
                return -1;

        for(i=0; !feof(fp) && i<size; i++)
        {
                buf[i] = fgetc(fp);
        }

        buf[i] = 0x00;

        fclose(fp);

        return i;
}

int main()
{
        FILE *fp = NULL;
        cJSON *json = NULL;
        char *filename = "./exapmle.json";
        char *out;
        char *buf = NULL;
        int len = file_size(filename);

        if(len <= 0)
                return -1;

        buf = malloc(len+1);

        if(buf == NULL)
        {
                printf("内存不足\n");
                return -1;
        }

        len = read_all("./1.json", buf, len);

        json = cJSON_Parse(buf);

        if(!json)
        {
                printf("Error before: [%s]\n",cJSON_GetErrorPtr());
                return -1;
        }

        out = cJSON_Print(json);                //这个是可以输出的。为获取的整个json的值

        cJSON *arrayItem = cJSON_GetObjectItem(json,"syslog_db");               //获取这个对象成员
        cJSON *object = cJSON_GetArrayItem(arrayItem,0);                        //因为这个对象是个数组获取，且只有一个元素所以写下标为0获取

        /*下面就是可以重复使用cJSON_GetObjectItem来获取每个成员的值了*/
        cJSON *item = cJSON_GetObjectItem(object,"db_user");  //
        printf("db_user:%s\n",item->valuestring);

        item = cJSON_GetObjectItem(object,"db_password");
        printf("db_password:%s\n",item->valuestring);

        item = cJSON_GetObjectItem(object,"db_type");
        printf("db_type:%s\n",item->valuestring);

        item = cJSON_GetObjectItem(object,"db_ip");
        printf("db_ip:%s\n",item->valuestring);

        item = cJSON_GetObjectItem(object,"db_port");
        printf("db_port:%s\n",item->valuestring);

        item = cJSON_GetObjectItem(object,"db_name");
        printf("db_name:%s\n",item->valuestring);

        item = cJSON_GetObjectItem(object,"sql");
        printf("db_sql:%s\n",item->valuestring);

        /*这里这个是直接可以获取值的*/
        arrayItem = cJSON_GetObjectItem(json,"syslog_enable");
        printf("%s\n",arrayItem->valuestring);

        cJSON_Delete(json);

        free(buf);

        return 0;
}

2.json文件

{
        "syslog_db":
                [{"db_user": "xxx",
                        "db_password": "yyy",
                        "db_type": "ORACLE",
                        "db_ip":"172.16.1.248",
                        "db_port":"1521",
                        "db_name":"orcl",
                        "sql":"select * from syslog"
                }],
        "syslog_source":
                [{"send_ip":"172.0.0.8",
                        "send_port":"8",
                        "send_protocal":"TCP"
                }],
        "syslog_enable":"1"
}

4.编译源码

$ gcc -o example example.c -L$HOME/local/lib -lcjson

5.运行程序

$ ./example
db_user:xxx
db_password:yyy
db_type:ORACLE
db_ip:172.16.1.248
db_port:1521
db_name:orcl
db_sql:select * from syslog
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