示例代码：
#include <FS.h> //this needs to be first, or it all crashes and burns...
#include <ESP8266WiFi.h> //https://github.com/esp8266/Arduino
//needed for library
#include <DNSServer.h>
#include <ESP8266WebServer.h>
#include <WiFiManager.h> //https://github.com/tzapu/WiFiManager
#include <ArduinoJson.h> //https://github.com/bblanchon/ArduinoJson
//define your default values here, if there are different values in config.json, they are overwritten.
char mqtt_server[40];
char mqtt_port[6] = "8080";
char blynk_token[34] = "YOUR_BLYNK_TOKEN";
//flag for saving data
bool shouldSaveConfig = false;
//callback notifying us of the need to save config
void saveConfigCallback () {
Serial.println("Should save config");
shouldSaveConfig = true;
}
void setup() {
// put your setup code here, to run once:
Serial.begin(115200);
Serial.println();
//clean FS, for testing
//SPIFFS.format();
//read configuration from FS json
Serial.println("mounting FS...");
if (SPIFFS.begin()) {
Serial.println("mounted file system");
if (SPIFFS.exists("/config.json")) {
//file exists, reading and loading
Serial.println("reading config file");
File configFile = SPIFFS.open("/config.json", "r");
if (configFile) {
Serial.println("opened config file");
size_t size = configFile.size();
// Allocate a buffer to store contents of the file.
std::unique_ptr<char[]> buf(new char[size]);
configFile.readBytes(buf.get(), size);
DynamicJsonBuffer jsonBuffer;
JsonObject& json = jsonBuffer.parseObject(buf.get());
json.printTo(Serial);
if (json.success()) {
Serial.println("\nparsed json");
strcpy(mqtt_server, json["mqtt_server"]);
strcpy(mqtt_port, json["mqtt_port"]);
strcpy(blynk_token, json["blynk_token"]);
} else {
Serial.println("failed to load json config");
}
}
}
} else {
Serial.println("failed to mount FS");
}
//end read
// The extra parameters to be configured (can be either global or just in the setup)
// After connecting, parameter.getValue() will get you the configured value
// id/name placeholder/prompt default length
WiFiManagerParameter custom_mqtt_server("server", "mqtt server", mqtt_server, 40);
WiFiManagerParameter custom_mqtt_port("port", "mqtt port", mqtt_port, 5);
WiFiManagerParameter custom_blynk_token("blynk", "blynk token", blynk_token, 32);
//WiFiManager
//Local intialization. Once its business is done, there is no need to keep it around
WiFiManager wifiManager;
//set config save notify callback
wifiManager.setSaveConfigCallback(saveConfigCallback);
//set static ip
wifiManager.setSTAStaticIPConfig(IPAddress(10,0,1,99), IPAddress(10,0,1,1), IPAddress(255,255,255,0));
//add all your parameters here
wifiManager.addParameter(&custom_mqtt_server);
wifiManager.addParameter(&custom_mqtt_port);
wifiManager.addParameter(&custom_blynk_token);
//reset settings - for testing
//wifiManager.resetSettings();
//set minimu quality of signal so it ignores AP's under that quality
//defaults to 8%
//wifiManager.setMinimumSignalQuality();
//sets timeout until configuration portal gets turned off
//useful to make it all retry or go to sleep
//in seconds
//wifiManager.setTimeout(120);
//fetches ssid and pass and tries to connect
//if it does not connect it starts an access point with the specified name
//here "AutoConnectAP"
//and goes into a blocking loop awaiting configuration
if (!wifiManager.autoConnect("AutoConnectAP", "password")) {
Serial.println("failed to connect and hit timeout");
delay(3000);
//reset and try again, or maybe put it to deep sleep
ESP.reset();
delay(5000);
}
//if you get here you have connected to the WiFi
Serial.println("connected...yeey :)");
//read updated parameters
strcpy(mqtt_server, custom_mqtt_server.getValue());
strcpy(mqtt_port, custom_mqtt_port.getValue());
strcpy(blynk_token, custom_blynk_token.getValue());
//save the custom parameters to FS
if (shouldSaveConfig) {
Serial.println("saving config");
DynamicJsonBuffer jsonBuffer;
JsonObject& json = jsonBuffer.createObject();
json["mqtt_server"] = mqtt_server;
json["mqtt_port"] = mqtt_port;
json["blynk_token"] = blynk_token;
File configFile = SPIFFS.open("/config.json", "w");
if (!configFile) {
Serial.println("failed to open config file for writing");
}
json.printTo(Serial);
json.printTo(configFile);
configFile.close();
//end save
}
Serial.println("local ip");
Serial.println(WiFi.localIP());
}
void loop() {
// put your main code here, to run repeatedly:
}
我从这里（https://techtutorialsx.com/2017/01/08/esp8266-posting-json-data-to-a-flask-server-on-the-cloud/）得到了这段代码：
HTTPClient http; //Declare object of class HTTPClient
http.begin("http://anteph.pythonanywhere.com/postjson"); //Specify request destination
http.addHeader("Content-Type", "application/json"); //Specify content-type header
int httpCode = http.POST(JSONmessageBuffer); //Send the request
String payload = http.getString(); //Get the response payload
Serial.println(httpCode); //Print HTTP return code
Serial.println(payload); //Print request response payload
http.end(); //Close connection
但是如果我使用：
int httpCode = http.POST(JSONmessageBuffer); //Send the request
这将发送所有json数据（即mqtt_server，mqtt_port，blynk_token）。但是我只想发送“ blynk_token”而不发送其余的json数据到服务器，那么如何实现呢？
请提出建议。
答案 0 :(得分：0)
因此，要回答有关“如何使用DynamicJsonBuffer从SPIFF读取和写入有限的Json数据”的问题，您可以在此处读取数据的地方查看代码。
if (configFile) {
Serial.println("opened config file");
size_t size = configFile.size();
// Allocate a buffer to store contents of the file.
std::unique_ptr<char[]> buf(new char[size]);
configFile.readBytes(buf.get(), size);
DynamicJsonBuffer jsonBuffer;
JsonObject& json = jsonBuffer.parseObject(buf.get());
json.printTo(Serial);
if (json.success()) {
Serial.println("\nparsed json");
strcpy(mqtt_server, json["mqtt_server"]); // copy mqtt_server value
strcpy(mqtt_port, json["mqtt_port"]); // copy mqtt_port value
strcpy(blynk_token, json["blynk_token"]); // copy blynk_token value
} else {
Serial.println("failed to load json config");
}
}
在这段代码之后，您将3个变量填充为值。
它们是mqtt_server，mqtt_port和blynk_token，它们现在包含从保存在SPIFF中的json读取的值。
如果您随后要将blynk_token发送到本地服务器，则只需要将该变量放入JSONmessageBuffer中即可。
像这样：
StaticJsonBuffer<300> JSONbuffer; //Declaring static JSON buffer
JsonObject& JSONencoder = JSONbuffer.createObject();
JSONencoder["blynk_token"] = blynk_token; // add blynk_token to the values sent to the server
char JSONmessageBuffer[300];
JSONencoder.prettyPrintTo(JSONmessageBuffer, sizeof(JSONmessageBuffer));
Serial.println(JSONmessageBuffer);
HTTPClient http; //Declare object of class HTTPClient
http.begin("http://anteph.pythonanywhere.com/postjson"); //Specify request destination
http.addHeader("Content-Type", "application/json"); //Specify content-type header
int httpCode = http.POST(JSONmessageBuffer); //Send the request
String payload = http.getString(); //Get the response payload
Serial.println(httpCode); //Print HTTP return code
Serial.println(payload); //Print request response payload
http.end(); //Close connection
此行JSONencoder["blynk_token"] = blynk_token;是您要走的路。在这里，您说要发送到服务器的值。
此tutorial可能也对您有帮助：）