Example of JSON Serialize and Deserialize in ESP-IDF
Example of JSON Serialize and Deserialize with ESP-IDF.
ESP-IDF includes this cJSON library.
You can use JSON components as standard.
But the documentation is very poor.
The official documentation for the JSON component is here.
Here is a example by Dave Gamble.
git clone https://github.com/nopnop2002/esp-idf-json
cd esp-idf-json/json-basic-object
idf.py flash monitor
From print_value() function, the pointer returned is allocated by cJSON_strdup() and it is returned to the caller.
Buffers returned by cJSON_Print must be freed by the caller.
Please use the proper API (cJSON_free) rather than directly calling stdlib free.
char *my_json_string = cJSON_Print(root);
ESP_LOGI(TAG, "my_json_string\n%s",my_json_string);
cJSON_Delete(root);
cJSON_free(my_json_string);
Array
Array, like this, have no name.
Array starts with [ and ends with ].
root is defined by cJSON_CreateArray.
element is added by cJSON_AddItemToArray.
["abc", 123, true, false, null]
Object
Object, like this, have name.
Object starts with { and ends with }.
root is defined by cJSON_CreateObject.
element is added by cJSON_AddItemToObject.
{
"version": "v5.0-dev-3202-ga2d5041492-dirty",
"cores": 2,
}
Object in Array
["abc", 123, true, false, null, {
"version": "v5.0-dev-3202-ga2d5041492-dirty",
"cores": 2
}]
[{
"id": 0,
"version": "v5.0-dev-3202-ga2d5041492-dirty",
"cores": 2
}, {
"id": 1,
"version": "v5.0-dev-3202-ga2d5041492-dirty",
"cores": 2
}]
Array in Array
[["abc", 120], ["abc", 121], ["abc", 122], ["abc", 123], ["abc", 124], ["abc", 125], ["abc", 126], ["abc", 127], ["abc", 128], ["abc", 129]]
Object in Object
{
"name": "Jack (\"Bee\") Nimble",
"format": {
"type": "rect",
"width": 1920,
"height": 1080,
"interlace": false,
"frame rate": 24
}
}
Array in Object
{
"version": "v5.0-dev-3202-ga2d5041492-dirty",
"cores": 2,
"array": ["abc", 123, true, false, null]
}
Object in Array in Object
{
"version": "v5.0-dev-3202-ga2d5041492-dirty",
"cores": 2,
"array": [{
"width": 1280,
"height": 720
}, {
"width": 1920,
"height": 1080
}, {
"width": 3840,
"height": 2160
}]
}
Array in Object in Array
[{
"id": 0,
"version": "v5.0-dev-3202-ga2d5041492-dirty",
"cores": 2,
"array": ["abc", 123, true, false, null]
}, {
"id": 1,
"version": "v5.0-dev-3202-ga2d5041492-dirty",
"cores": 2,
"array": ["abc", 123, true, false, null]
}]
Serialization starts from the lowest level.
No matter how complex the structure, there are only objects and arrays.
Target structure
{
"version": "v5.0-dev-3202-ga2d5041492-dirty",
"cores": 2,
"array": [{
"width": 1280,
"height": 720
}, {
"width": 1920,
"height": 1080
}, {
"width": 3840,
"height": 2160
}]
}
Create 3 objects
This is simple object.
{
"width": 1280,
"height": 720
}
{
"width": 1920,
"height": 1080
}
{
"width": 3840,
"height": 2160
}
Create array
This is object in array.
[{
"width": 1280,
"height": 720
}, {
"width": 1920,
"height": 1080
}, {
"width": 3840,
"height": 2160
}]
Create object as root
This is array in object.
{
"version": "v5.0-dev-3202-ga2d5041492-dirty",
"cores": 2,
"array": [{
"width": 1280,
"height": 720
}, {
"width": 1920,
"height": 1080
}, {
"width": 3840,
"height": 2160
}]
}
Target structure
[{
"id": 0,
"version": "v5.0-dev-3202-ga2d5041492-dirty",
"cores": 2,
"array": ["abc", 123, true, false, null]
}, {
"id": 1,
"version": "v5.0-dev-3202-ga2d5041492-dirty",
"cores": 2,
"array": ["abc", 123, true, false, null]
}]
Create 2 arrays
This is simple array.
["abc", 123, true, false, null]
["abc", 123, true, false, null]
Create 2 objects
This is array in object.
{
"id": 1,
"version": "v5.0-dev-3202-ga2d5041492-dirty",
"cores": 2,
"array": ["abc", 123, true, false, null]
}
{
"id": 0,
"version": "v5.0-dev-3202-ga2d5041492-dirty",
"cores": 2,
"array": ["abc", 123, true, false, null]
}
Create array as root
This is object in array.
[{
"id": 0,
"version": "v5.0-dev-3202-ga2d5041492-dirty",
"cores": 2,
"array": ["abc", 123, true, false, null]
}, {
"id": 1,
"version": "v5.0-dev-3202-ga2d5041492-dirty",
"cores": 2,
"array": ["abc", 123, true, false, null]
}]
This is a sample JSON data set.
https://opensource.adobe.com/Spry/samples/data_region/JSONDataSetSample.html