Jansson库的使用简介

一、Jansson的安装：

二、jansson相关的API：

https://jansson.readthedocs.io/en/latest/apiref.html#c.json_t

string

object

array

error

number

三、jansson实际如何处理JSON文件：

 #include <iostream>
 #include "jansson.h"
 #include <string.h>
 #include <stdio.h>
 #include <stdlib.h>

 using namespace std;

 int main() {
     json_t val;
     json_type eval = JSON_REAL;
     bool Judge = ;
     int type = json_typeof(&val);
     Judge = json_is_object(&val);
     cout << "json_is_object:" << Judge << endl;
     Judge = json_is_array(&val);
     cout << "Json_is_array:" << Judge << endl;
     cout << "The type of val:" << type << endl;

     json_t *array, *integer;
     array = json_array(); // Create the json array
     integer = json_integer(); // Create the json integer
     json_array_append(array,integer);
     json_decref(integer);

     /* JSON-STRING */
     json_auto_t *value = NULL;
     value = json_string("Hello");
     json_string_set(value, "World!");
     size_t len = json_string_length(value);
     cout << "The len of value:" << len << endl;

     /* JSON-NUMBER */
     json_int_t number;
     number = ;
     printf("number is %" JSON_INTEGER_FORMAT "\n",number);
     number = json_integer_value(integer);
     printf("value of integer(json_t) is %" JSON_INTEGER_FORMAT "\n",number);
     integer = json_real(3.1415926);
     double res = json_real_value(integer);
     printf("The res is:%f\n",res);

     /* JSON-ARRAY */
     json_t *Matrix = json_array();
     json_array_append(Matrix,integer);
     size_t Matrix_Size = json_array_size(Matrix);
     printf("The size of Matrix:%d\n",Matrix_Size);

     /* JSON-OBJECT */
     json_t *obj = json_object();
     size_t obj_size = json_object_size(obj);
     printf("The size of obj:%d\n",obj_size);
     char *key = "Hello";
     int back = json_object_set(obj,key,&val);
     printf("The json_object_set correct?%d\n",back);

     json_t *json_file;
     json_error_t error;

     /* Use the abs-route of the file can read the json file crectlly */
     json_file = json_load_file("/home/ubuntu-bitmain/workspace/TestCpp/src/cpuminer-conf.json", , &error);
     if(!json_file) printf("No json_file can read!\n");
     obj_size = json_object_size(json_file);
     printf("The size of json_file:%d\n",obj_size);
     json_t *url,*user,*pass;
     char *Key_0 = "url";
     char *Key_1 = "user";
     char *Key_2 = "pass";
     url = json_object_get(json_file,Key_0);
     user = json_object_get(json_file,Key_1);
     pass = json_object_get(json_file,Key_2);

     Judge = json_is_string(url);
     size_t str_length = json_string_length(url);
     cout << "The length of url is:" << str_length << endl;
     const char *str_res_0 = " ";
     str_res_0 = json_string_value(url);
     cout << "The length of url is:" << strlen(str_res_0) << endl;
     for(int i=;i<strlen(str_res_0);i++){
         cout << *(str_res_0+i);
     }
     cout << endl;
     cout << "The url is string" << Judge << endl;

     return ;
 }

四、从网上获取JSON文件并解析：

完~