安装jansson 步骤：
http://blog.csdn.net/lz909/article/details/46042979
jansson 手册：
https://jansson.readthedocs.io/en/latest/index.html
API 介绍：
http://jansson.readthedocs.io/en/2.2/apiref.html#json_error_t
string object array error number
#include <stdio.h>
#include <stdlib.h>
#include <stdfix.h>
#include <string.h>
#include <iostream>
#include <jansson.h>
#include <jansson_config.h>
using namespace std;
int main() {
json_t val;
json_type eval = JSON_REAL;
bool Judge = 1;
int type = json_typeof(&val); // Get the type of Obj
Judge = json_is_object(&val); // Obj Judge
cout << "json_is_object:" << Judge << endl;
Judge = json_is_array(&val); //Object judged to be array
cout << "Json_is_array:" << Judge << endl;
cout << "The type of val:" << type << endl;
/* JSON array Defination and value setting */
json_t *array, *integer;
array = json_array(); // Create the json array
integer = json_integer(42); // Create the json integer
json_array_append(array,integer); // Set the value of json array
json_decref(integer); // Drop the content of integer and can no longer be used.
/* JSON-STRING */
json_auto_t *value = NULL;
value = json_string("Hello"); // Initial a new string json obj
json_string_set(value, "World!"); // Use set func to change the content of json string obj.
size_t len = json_string_length(value); // Get the length of the json string obj.
cout << "The len of value:" << len << endl;
/* JSON-NUMBER */
json_int_t number; // Define a json type number.
number = 100; // initial the number.
printf("number is %" JSON_INTEGER_FORMAT "\n",number);
number = json_integer_value(integer); // Get the json type integer's value to number.
printf("value of integer(json_t) is %" JSON_INTEGER_FORMAT "\n",number); // The integer had been decrefed in line27.(So it's zero)
integer = json_real(3.1415926); // Set a real number value to integer.
double res = json_real_value(integer); // Read out the value to a double type var.(The integer can store the double type json data.)
printf("The res is:%f\n",res);
/* JSON-ARRAY */
json_t *Matrix = json_array(); // json array defination.
json_array_append(Matrix,integer); // Add a integer obj to the array.
size_t Matrix_Size = json_array_size(Matrix); // Test the size of the array after add a new integer obj to it.
printf("The size of Matrix:%d\n",Matrix_Size);
/* JSON-OBJECT */
json_t *obj = json_object(); // Define a new json obj.
size_t obj_size = json_object_size(obj); // Get the size of the json obj.
printf("The size of obj:%d\n",obj_size);
char *key = "Hello";
integer = json_integer(52); // Set the value of integer json obj.
int back = json_object_set(obj,key,integer); // Setup a new obj named "Hello" and the mapped value is 52.
json_t *read_num_back = json_object_get(obj,key); // Get back the obj named "Hello".
int num_val = json_integer_value(read_num_back); // Get the value of the Hello obj.
cout << "The value of integer:" << num_val << endl; // Echo out the Value.
while(1);
return 0;
}
#include<stdio.h>
#include<string.h>
#include<jansson.h>
#define FILE_PATH "./temp.txt"
#define MAX_NUM 5
typedef struct _JSON_ITEM_INFO
{
json_t* string;
json_t* value;
}JSON_ITEM_INFO;
void save_info_to_file()
{
json_t* root = NULL;
json_t* item_1 = NULL;
json_t* item_2 = NULL;
json_t* item_3 = NULL;
json_t* array = NULL;
char* s_repon = NULL;
root = json_object();
item_1 = json_object();
item_2 = json_object();
item_3 = json_object();
array = json_array();
json_object_set_new(item_1,"name",json_string("xiaopeng"));
json_object_set_new(item_1,"age",json_integer(12));
json_array_append_new(array,item_1);
json_object_set_new(item_2,"name",json_string("xiaoming"));
json_object_set_new(item_2,"age",json_integer(8));
json_array_append_new(array,item_2);
json_object_set_new(item_3,"name",json_string("xiaohong"));
json_object_set_new(item_3,"age",json_integer(22));
json_array_append_new(array,item_3);
json_object_set_new(root,"root",array);
json_dump_file(root, FILE_PATH,JSON_PRESERVE_ORDER);
s_repon = json_dumps(root,JSON_INDENT(0));
printf("s_repon = %s \n",s_repon);
free(s_repon);
printf("size = %d \n", (int)json_array_size(array));
if(root)
{
json_delete(root);
}
if(array)
{
json_delete(array);
}
}
void get_file_info()
{
int i = 0;
json_t* root = NULL;
json_t* array = NULL;
json_error_t error;
char* s_repon = NULL;
json_t* add_item_1 = NULL;
char* s_get_add_item = NULL;
json_t* rec_table[MAX_NUM] = {0};
JSON_ITEM_INFO person[MAX_NUM];
memset(person,0,sizeof(person));
//get the info from file;
root = json_load_file(FILE_PATH, 0, &error);
if(!json_is_object(root))
{
printf("%s,%d\n",__FILE__,__LINE__);
}
s_repon = json_dumps(root,JSON_INDENT(0));
printf("s_repon = %s \n",s_repon);
free(s_repon);
array = json_object_get(root,"root");
if(!json_is_array(array))
{
printf("%s,%d\n",__FILE__,__LINE__);
}
for(i = 0; i < MAX_NUM ;i++)
{
rec_table[i] = json_array_get(array,i);
if(!json_is_object(rec_table[i]))
{
printf("%s,%d\n",__FILE__,__LINE__);
}
person[i].string = json_object_get(rec_table[i],"name");
printf("person[%d].string = %s \n",i,json_string_value(person[i].string));
person[i].value = json_object_get(rec_table[i],"age");
printf("person[%d].value = %d \n",i,(int)json_integer_value(person[i].value));
}
//add the new item;
add_item_1 = json_object();
json_object_set_new(add_item_1,"name",json_string("zhangsan"));
json_object_set_new(add_item_1,"age",json_integer(30));
if(json_array_size(array) >= MAX_NUM)
{
//remove the top item;
json_array_remove(array,0);
}
json_array_append_new(array,add_item_1);
//write the new array to the file;
json_dump_file(root, FILE_PATH,JSON_PRESERVE_ORDER);
//dump the date and print
s_get_add_item = json_dumps(root,JSON_INDENT(0));
printf("s_get_add_item = %s \n",s_get_add_item);
free(s_get_add_item);
}
int main()
{
save_info_to_file(); //这里将数据保存在文件 FILE_PATH 里；
get_file_info(); // 这里将文件 FILE_PATH 数据读取出来；
return 0;
}
编译：
gcc source.c -ljansson