String section="header";
while(client.available()){
String line = client.readStringUntil('\r');
//Serial.print(line);
// we’ll parse the HTML body here
if (section=="header") { // headers..
//Serial.print("");
if (line=="\n") { // skips the empty space at the beginning
section="json";
}
}
else if (section=="json") { // print the good stuff
section="ignore";
String result = line.substring(1);
// Parse JSON
int size = result.length() + 1;
char json[size];
result.toCharArray(json, size);
StaticJsonBuffer<500> jsonBuffer;
JsonObject& json_parsed = jsonBuffer.parseObject(json);
if (!json_parsed.success())
{
Serial.println("parseObject() failed");
return;
}
// Fetch values.
//
// Most of the time, you can rely on the implicit casts.
// In other case, you can do root["time"].as<long>();
const char* led = json_parsed["led"];
const char* stat = json_parsed["stat"];
Serial.print("Led = ");
Serial.println(led);
Serial.print("Status = ");
Serial.println(stat);
Can someone help me please..
sorry my english is not so good..
wow - never seen so much use of The String class, even yours state machine is done using Strings... hopefully you are running this code on a very large modern arduino with tons of RAM ...
especially since you duplicate your string just to get rid of the first char, then duplicate that again in a stack allocated char array and then building a huge json buffer for decoding... (c_str() on the string object would give you the pointer to the buffer, so char * result = line.c_str() +1; would be saving some memory already)
Seriously I would recommend to trash all that code with the String object, use an enum and byte for state management especially if you are on a standard arduino and use char arrays, strtok, etc for parsing. Not sure about your Json library, but this one is pretty effective
And for building up knowledge you should also read The Evils of Arduino Strings so that you understand what you do with all those Strings. (There are no good or wrong tools, just need to use them when they are appropriate, in the right context, and in full understanding of benefits/drawbacks)
Thanks for all the responses..
This takes some time for me to understand, because I am new to raduino, and this is the progress that I get..
I read why parsing fail from j-m-l .. and got a hint that if I use the array, the sample code used is like this :
[{"hello":"world"}]
JsonArray& root = jsonBuffer.parseArray(json);
const char* world = root[0]["hello"];
and this was previous led program, which has now been edited..
// Copyright Benoit Blanchon 2014-2016
// MIT License
//
// Arduino JSON library
// https://github.com/bblanchon/ArduinoJson
// If you like this project, please add a star!
#include <ArduinoJson.h>
;
void setup() {
Serial.begin(9600);
while (!Serial) {
// wait serial port initialization
}
char json[] = "[{\"led\":\"1\",\"stat\":\"on\"},{\"led\":\"2\",\"stat\":\"off\"},{\"led\":\"3\",\"stat\":\"on\"},{\"led\":\"4\",\"stat\":\"off\"}]";
//
// Step 1: Reserve memory space
//
StaticJsonBuffer<200> jsonBuffer;
//
// Step 2: Deserialize the JSON string
//
JsonArray& root = jsonBuffer.parseArray(json);
if (!root.success())
{
Serial.println("parseObject() failed");
return;
}
//
// Step 3: Retrieve the values
//
if (strcmp(root[0]["led"], "1") == 0) {
const char* led = root[0]["led"];
const char* stat = root[0]["stat"];
Serial.print ("LED = ");
Serial.println (led);
Serial.print ("Status = ");
Serial.println (stat);
}
if (strcmp(root[1]["led"], "2") == 0) {
const char* led = root[1]["led"];
const char* stat = root[1]["stat"];
Serial.print ("LED = ");
Serial.println (led);
Serial.print ("Status = ");
Serial.println (stat);
}
if (strcmp(root[2]["led"], "3") == 0) {
const char* led = root[2]["led"];
const char* stat = root[2]["stat"];
Serial.print ("LED = ");
Serial.println (led);
Serial.print ("Status = ");
Serial.println (stat);
}
if (strcmp(root[3]["led"], "4") == 0) {
const char* led = root[3]["led"];
const char* stat = root[3]["stat"];
Serial.print ("LED = ");
Serial.println (led);
Serial.print ("Status = ");
Serial.println (stat);
}
else {
Serial.println("No Data");
}
}
void loop() {
// not used in this example
}
output from serial monitor :
LED = 1
Status = on
LED = 2
Status = off
LED = 3
Status = on
LED = 4
Status = off
no, I mean I still don't understand how to pointing the order of objects in its array. so what variables should I use to pointing the order of objects in the array, and is used for looping.
here is an example on how to parse exactly your structure - IT EXPECTS YOUR STRUCTURE AS IS (number of leds can vary)
#include <ArduinoJson.h>
void setup() {
Serial.begin(115200);
char json[] = "[{\"led\":\"1\",\"stat\":\"on\"},{\"led\":\"2\",\"stat\":\"off\"},{\"led\":\"3\",\"stat\":\"on\"},{\"led\":\"4\",\"stat\":\"off\"}]";
//
// Step 1: Reserve memory space
//
StaticJsonBuffer<200> jsonBuffer;
//
// Step 2: Deserialize the JSON string
//
JsonArray& root = jsonBuffer.parseArray(json); //parseArray() returns a reference to a JsonArray
if (!root.success()) {
Serial.println("parseObject() failed");
return;
}
//
// Step 3: Retrieve the values
//
Serial.println("--------------------------");
for (int i = 0; i < sizeof(root); i++) {
Serial.println(i);
// extracting strings
Serial.print("\tled "); Serial.print(root[i]["led"].as<char*>());
Serial.print(" is "); Serial.println(root[i]["stat"].as<char*>());
// or extracting numerical data
int led = root[i]["led"].as<long>();
byte ledStatus;
if (!strcmp(root[i]["stat"].as<char*>(), "on")) ledStatus = HIGH; else ledStatus = LOW;
Serial.print ("\tled "); Serial.print (led); Serial.print (" is "); Serial.println (ledStatus);
Serial.println("--------------------------");
}
}
void loop() {}
I print things twice, one by extracting the value from a given key as a c string (char*) and the second time for the led as a number + I use the strcmp() function to build out a value if my LED is HIGH or LOW
that will print out the following: (need to set your console at 115200 bauds)
--------------------------
0
led 1 is on
led 1 is 1
--------------------------
1
led 2 is off
led 2 is 0
--------------------------
2
led 3 is on
led 3 is 1
--------------------------
3
led 4 is off
led 4 is 0
--------------------------
