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Esp8266 --- JSON data exchange format
2022-07-27 01:24:00 【Paradise_ Violet】
Catalog
establish JSON Tree callback function
analysis JSON Tree callback function
Preface
Introduce 8266 How to create and parse JSON character string ---- Provided by Lexin API
JSON: JavaSeript Object Notation == JS Object harmonic ： It is essentially a data exchange format
advantage ： Completely independent of programming language 、 Convenient for us to read and write , It is also convenient for machine parsing and generation .
effect ： Store data and represent data . Communication parties can use JSON String format to transmit text information .
JSON It's made up of many elements , Elements are marked with specific symbols .
{} Curly braces denote objects [] Brackets indicate arrays "" Inside the double quotation marks are attributes ( key ) Or value： The front represents the attribute ( key ） ： The latter represents the specific value of this attribute
example : ( "temp": "30°C" } "temp” Is an attribute , It means temperature .
“30°C” Is the value of this attribute , Indicates that the current temperature is "30°C”notes ：
【" key "】 Must be " character string "
【“ value "】 It can be 【〝 character string ”、 Array []、 object {}、 Numbers 】（ The number is ASCII Code form
user_init
void ICACHE_FLASH_ATTR user_init(void)
{
uart_init(115200,115200); // Initialize the serial port baud rate
os_delay_us(10000); // Wait for the serial port to stabilize
os_printf("\r\n=================================================\r\n");
os_printf("\t Project:\t%s\r\n", ProjectName);
os_printf("\t SDK version:\t%s", system_get_sdk_version());
os_printf("\r\n=================================================\r\n");
Setup_JSON_Tree_JX(); // establish JSON Trees
Parse_JSON_Tree_JX(); // analysis JSON Trees
}establish JSON Trees
call json_ws_send((struct jsontree_value *)&Object_JOSN, "K_JOSN", A_JSON_Tree); To create JSON Tree parameters 1： The first JSON Object pointer / Parameters 2： The first JSON Object's key / Parameters 3：JSON Tree cache pointer , But call this API Before , Let's first create JSON The tree can call the following macro definition JSONTREE_OBJECT(Object_JOSN,JSONTREE_PAIR("K_JOSN", &V_JSON)); // Generate JOSN object The first of JSON Object name , Parameters 23456 All are json The key/value pair , We can call JSONTREE_PAIR("K_JOSN", &V_JSON) To create key value pairs , The first parameter is the key , The second parameter is the value , The value here can be the address of another object . His object name is Object_JOSN, Key value pairs are "K_JOSN" : { &V_JSON }
But pay attention to calling JSONTREE_OBJECT This API The first one created json Its object name and key will not be displayed, only { &V_JSON } Value
// notes ：JSONTREE_OBJECT( Parameters 1, Parameters 2, Parameters 3, ... ) //【 Parameters 1： Generated JSON The name of the tree object 】、【 Parameters 2： Key value pair 】、【 Parameters 3： Key value pair 】... //--------------------------------------------------------------------------- //【 Object name ：Object_JOSN Key value pair ："K_JOSN" : { &V_JSON } 】 //【 notes ： The first of JSON Object name 、" key " None of them . Display only ：{ &V_JSON } 】 //---------------------------------------------------------------------------------- JSONTREE_OBJECT(Object_JOSN,JSONTREE_PAIR("K_JOSN", &V_JSON)); // Generate JOSN objectNext, we are creating the value of the first object V_JSON Among them , Create three key value pairs, of which the value corresponding to the key Shanghai and Shenzhen is another object , This object is also two key value pairs , Temperature and humidity , We can call to create json Tree callback function , To set the value corresponding to the key
//【 Object name ：V_JSON Key value pair ："Shanghai":{ &V_Key_1 }, "Shenzhen":{ &V_Key_1 }, "result":{ &JSON_Tree_Set }】 //---------------------------------------------------------------------------------------------------------------- JSONTREE_OBJECT( V_JSON, JSONTREE_PAIR("Shanghai", &V_Key_1), JSONTREE_PAIR("Shenzhen", &V_Key_2), \ JSONTREE_PAIR("result", &JSON_Tree_Set) ); // Set up 【" key ":" value "】//【 Object name ：V_Key_1 Key value pair ："temp":{ &JSON_Tree_Set }, "humid":{ &JSON_Tree_Set }】 //【 Object name ：V_Key_2 Key value pair ："temp":{ &JSON_Tree_Set }, "humid":{ &JSON_Tree_Set }】 //-------------------------------------------------------------------------------------------------------------------------- JSONTREE_OBJECT(V_Key_1,JSONTREE_PAIR("temp", &JSON_Tree_Set),JSONTREE_PAIR("humid", &JSON_Tree_Set)); // Set up 【" key ":" value "】 JSONTREE_OBJECT(V_Key_2,JSONTREE_PAIR("temp", &JSON_Tree_Set),JSONTREE_PAIR("humid", &JSON_Tree_Set)); // Set up 【" key ":" value "】Let's look at creating JSON Tree callback function
// establish JSON Trees
//================================================================================
void ICACHE_FLASH_ATTR Setup_JSON_Tree_JX(void)
{
//【 establish JSON Trees 】
//【 Parameters 1： The first JSON Object pointer / Parameters 2： The first JSON Object's key / Parameters 3：JSON Tree cache pointer 】
//---------------------------------------------------------------------------
json_ws_send((struct jsontree_value *)&Object_JOSN, "K_JOSN", A_JSON_Tree);
os_printf("\r\n-------------------- establish JSON Trees -------------------\r\n");
os_printf("%s",A_JSON_Tree); // Serial printing JSON Trees
os_printf("\r\n-------------------- establish JSON Trees -------------------\r\n");
}
establish JSON Tree callback function
We can base on os_strncmp(P_Key_current, "result", os_strlen("result")) in “result” What is this key that is called later jsontree_write_string(js_ctx,"Shenzhen is too hot!"); This API To the corresponding key js_ctx Write the corresponding value
// establish JSON Tree callback function ：JSON Tree assignment
//【jsontree_path_name(...)： obtain JSON The corresponding depth of the tree 【" key "】 The pointer to 】
//【jsontree_write_string(...)： assignment JSON The corresponding depth of the tree 【" key "】( Assign values as strings )】
//【jsontree_write_atom(...)： assignment JSON The corresponding depth of the tree 【" key "】( Assign values in the form of numbers )】
//=======================================================================================================================
LOCAL int ICACHE_FLASH_ATTR JSON_AssignValue_Cb(struct jsontree_context *js_ctx) // ①： Definition generation JSON Functions of trees
{
const char * P_Key_current = jsontree_path_name(js_ctx,js_ctx->depth-1); // Gets a pointer to the current 【" key "】 The pointer to
if( os_strncmp(P_Key_current, "result", os_strlen("result")) == 0 ) // Judge the present 【" key "】 ?= "result"
{
jsontree_write_string(js_ctx,"Shenzhen is too hot!"); // take 【" value "="Shenzhen is too hot!"】 Write the corresponding position
}
else // At present 【" key "】 != "result", Judge the upper pointer
{
const char * P_Key_upper = jsontree_path_name(js_ctx,js_ctx->depth-2); // Get points to the previous layer 【" key "】 The pointer to
if(os_strncmp(P_Key_upper, "Shanghai", os_strlen("Shanghai")) == 0) // Judge the next level 【" key "】 ?= "Shanghai"
{
if(os_strncmp(P_Key_current, "temp", os_strlen("temp")) == 0) // Judge the present 【" key "】 ?= "temp"
{
jsontree_write_string(js_ctx,"30℃"); // take 【" value "="30℃"】 Write the corresponding position
}
if(os_strncmp(P_Key_current, "humid", os_strlen("humid")) == 0) // Judge the present 【" key "】 ?= "humid"
{
jsontree_write_string(js_ctx,"30%RH"); // take 【" value "="30%RH"】 Write the corresponding position
}
}
else if( os_strncmp(P_Key_upper, "Shenzhen", os_strlen("Shenzhen")) == 0 ) // Judge the next level 【" key "】 ?= "Shenzhen"
{
if(os_strncmp(P_Key_current, "temp", os_strlen("temp")) == 0) // Judge the present 【" key "】 ?= "temp"
{
jsontree_write_string(js_ctx,"35℃"); // take 【" value "="35℃"】 Write the corresponding position
}
if(os_strncmp(P_Key_current, "humid", os_strlen("humid")) == 0) // Judge the present 【" key "】 ?= "humid"
{
jsontree_write_atom(js_ctx,"50"); // take 【" value " = 50】 Write the corresponding position
}
}
}
return 0;
}When json After the tree is created , We need to parse json Trees
analysis JSON Trees
First call jsontree_setup This API Come and analyze json Connect with the tree , Then call json_parse(&js, A_JSON_Tree); This API Parsing json Trees
// analysis JSON Trees //===================================================================================================== void ICACHE_FLASH_ATTR Parse_JSON_Tree_JX(void) { struct jsontree_context js; // JSON Tree environment structure // And to be parsed JSON Connect with the tree //【 Parameters 1：JSON Tree environment structure pointer Parameters 2：JSON The second object name pointer of the tree Parameters 3：json_putchar function 】 //----------------------------------------------------------------------------------------------- jsontree_setup(&js, (struct jsontree_value *)&V_JSON, json_putchar); // analysis JSON Trees //【 Parameters 1：JSON Tree environment structure pointer Parameters 2： To parse JSON Pointer to the tree 】 json_parse(&js, A_JSON_Tree); // Execute this statement , The corresponding JSON Tree parsing callback function }
analysis JSON Tree callback function
We call
these API To set the corresponding keys to their values , Analyze it , And print with serial port
// analysis JSON Tree callback function
//========================================================================================================================================
int ICACHE_FLASH_ATTR JSON_Tree_Parse_Cb(struct jsontree_context *js_ctx, struct jsonparse_state *parser)
{
os_printf("\r\n-------------------- analysis JSON Trees -------------------\r\n");
int type; // Character type
char buffer[64] = {0}; // cache 【 value 】 Array of
type = jsonparse_next(parser); // 【{】：JSON The frame first character of the object
os_printf("%c\n", type);
type = jsonparse_next(parser); // 【 key N】： The first top key 【Shanghai】
if(type != 0) // Determine whether there is a string
{
if (type == JSON_TYPE_PAIR_NAME) // Judge whether it is 【 key N】
{
if (jsonparse_strcmp_value(parser, "Shanghai") == 0) // 【Shanghai】
{
os_printf("\t Shanghai{2} \n");
type = jsonparse_next(parser); // 【:】
type = jsonparse_next(parser); // 【{】
type = jsonparse_next(parser); // 【 key N】
if (jsonparse_strcmp_value(parser, "temp") == 0) // 【temp】
{
type = jsonparse_next(parser); // 【:】
type = jsonparse_next(parser); // 【"】
if (type == JSON_TYPE_STRING) // Judge whether it is 【"】
{
jsonparse_copy_value(parser, buffer, sizeof(buffer)); // obtain 【 key 】 Corresponding value
os_printf("\t\t temp: %s\n", buffer); // 【30℃】
}
type = jsonparse_next(parser); // 【,】
type = jsonparse_next(parser); // 【 key N】
if (jsonparse_strcmp_value(parser, "humid") == 0) // 【humid】
{
type = jsonparse_next(parser); // 【:】
type = jsonparse_next(parser); // 【"】
if (type == JSON_TYPE_STRING) // Judge whether it is 【"】
{
jsonparse_copy_value(parser, buffer, sizeof(buffer)); // obtain 【 key 】 Corresponding value
os_printf("\t\t humid: %s\n", buffer); // 【30%RH】
type = jsonparse_next(parser); // 【}】
type = jsonparse_next(parser); // 【,】
type = jsonparse_next(parser); //【 key N】： The second top key 【Shenzhen】
if (jsonparse_strcmp_value(parser, "Shenzhen") == 0) // 【Shenzhen】
{
os_printf("\t Shenzhen{2} \n");
jsonparse_next(parser); // 【:】
jsonparse_next(parser); // 【{】
jsonparse_next(parser); // 【 key N】
if (jsonparse_strcmp_value(parser, "temp") == 0) // 【temp】
{
type = jsonparse_next(parser); // 【:】
type = jsonparse_next(parser); // 【"】
if (type == JSON_TYPE_STRING) // Judge whether it is 【"】
{
jsonparse_copy_value(parser, buffer, sizeof(buffer)); // obtain 【 key 】 Corresponding value
os_printf("\t\t temp: %s\n", buffer); // 【35℃】
type = jsonparse_next(parser); // 【,】
type = jsonparse_next(parser); // 【 key N】
if (jsonparse_strcmp_value(parser, "humid") == 0) // 【humid】
{
type = jsonparse_next(parser); // 【:】
type = jsonparse_next(parser); // 【0】(" value " = The number )
if (type == JSON_TYPE_NUMBER) // Judge whether it is 【0】( The number == ASSIC Code form )
{
jsonparse_copy_value(parser, buffer, sizeof(buffer)); // obtain 【 key 】 Corresponding value
os_printf("\t\t humid: %s\n", buffer); // 【50%RH】
type = jsonparse_next(parser); // 【}】
type = jsonparse_next(parser); // 【,】
type = jsonparse_next(parser); //【 key N】： The third top key 【result】
if (jsonparse_strcmp_value(parser, "result") == 0) // 【result】
{
type = jsonparse_next(parser); // 【:】
type = jsonparse_next(parser); // 【"】
if (type == JSON_TYPE_STRING) // Judge whether it is 【"】
{
jsonparse_copy_value(parser, buffer, sizeof(buffer)); // obtain 【 key 】 Corresponding value
os_printf("\t result: %s\n", buffer); //【Shenzhen is too hot!】
type = jsonparse_next(parser); // 【}】：JSON The frame end character of the object
os_printf("%c\n", type);
}
}
}
}
}
}
}
}
}
}
}
}
}
os_printf("\r\n-------------------- analysis JSON Trees -------------------\r\n");
return 0;
} 
You can see the successful creation json Trees , And then to json The tree is parsed , explain 8266 call json dependent API Successfully created and resolved json Trees ,
Although we can use the relevant information officially provided by Lexin API To create and parse json character string , But you can see that it is very complicated , It is recommended to use c String related functions in the function library json String creation and parsing
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