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Merge pull request #126 from stefanhaustein/master
Add a simple HomeAssitant friendly REST server example.
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‎src/main/java/com/pi4j/examples/server/README.md‎

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A simple REST server that reports the measurements for all
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auto-detected I2C sensors as a simple JSON object.

‎src/main/java/com/pi4j/examples/server/SensorServer.java‎

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package com.pi4j.examples.server;
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import com.pi4j.Pi4J;
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import com.pi4j.context.Context;
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import com.pi4j.drivers.sensor.Sensor;
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import com.pi4j.drivers.sensor.SensorDescriptor;
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import com.pi4j.drivers.sensor.SensorDetector;
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import java.io.*;
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import java.net.InetSocketAddress;
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import java.net.ServerSocket;
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import java.net.Socket;
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import java.util.*;
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public class SensorServer {
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private static final int BUS = 1;
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private static final int PORT = 8147;
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private final ServerSocket serverSocket;
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private final List<Sensor> sensorList;
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private final String address;
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SensorServer(int port, List<Sensor> sensorList) throws IOException {
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serverSocket = new ServerSocket(port);
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this.sensorList = sensorList;
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try (
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Socket socket = new Socket();
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) {
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// Get our own address, see https://stackoverflow.com/a/41822127/1401879
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socket.connect(new InetSocketAddress("google.com", 80));
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address = "http:/" + socket.getLocalAddress() + ":" + port;
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}
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}
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void run() {
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while(true) {
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try(Socket socket = serverSocket.accept()) {
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BufferedReader in = new BufferedReader(new InputStreamReader(socket.getInputStream()));
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String request = in.readLine();
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System.out.println(new Date() + ": Request from " + socket.getRemoteSocketAddress() + ": " + request);
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while (true) {
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String line = in.readLine();
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if (line == null || line.isEmpty()) {
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break;
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}
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}
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Writer writer = new BufferedWriter(new OutputStreamWriter(socket.getOutputStream()));
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if (request == null || !request.startsWith("GET /")) {
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writer.write("HTTP/1.0 501 Error\r\n\r\n");
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} else {
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int end = request.lastIndexOf(' ');
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String path = request.substring(5, end);
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StringBuilder builder = new StringBuilder();
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String contentType = switch (path) {
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case "" -> renderHelp(builder);
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case "measurements" -> renderData(builder);
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case "config" -> renderConfig(builder);
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default -> null;
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};
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if (contentType == null) {
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writer.write("HTTP/1.0 404 Not Found\r\n\r\n");
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} else {
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writer.write("HTTP/1.0 200 OK\r\n");
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writer.write("Content-Type: " + contentType + "; charset=utf-8\r\n\r\n");
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writer.write(builder.toString());
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}
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}
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writer.close();
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} catch (IOException e) {
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e.printStackTrace();
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}
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}
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}
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String renderData(StringBuilder sb) {
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boolean first = true;
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sb.append("{");
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Map<String, Integer> names = new HashMap<>();
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for (Sensor sensor : sensorList) {
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SensorDescriptor descriptor = sensor.getDescriptor();
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List<SensorDescriptor.Value> valueDescriptors = descriptor.getValues();
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float[] measurements = new float[valueDescriptors.size()];
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sensor.readMeasurement(measurements);
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for (SensorDescriptor.Value valueDescriptor : valueDescriptors) {
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sb.append(first ? "\n " : ",\n ");
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first = false;
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sb.append('"');
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sb.append(getUniqueName(names, valueDescriptor));
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sb.append("\": ");
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sb.append(measurements[valueDescriptor.getIndex()]);
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}
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}
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sb.append("\n}\n");
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return "application/json";
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}
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String renderConfig(StringBuilder sb) {
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// https://www.home-assistant.io/integrations/sensor.rest/
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sb.append("# Add this snippet to the 'rest:' section in your HomeAssistant config.yaml:\n");
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sb.append("# rest:\n");
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sb.append(" - resource: \"").append(address).append("/measurements\"\n");
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sb.append(" sensor:\n");
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Map<String, Integer> names = new HashMap<>();
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for (Sensor sensor : sensorList) {
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SensorDescriptor descriptor = sensor.getDescriptor();
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List<SensorDescriptor.Value> valueDescriptors = descriptor.getValues();
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float[] measurements = new float[valueDescriptors.size()];
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sensor.readMeasurement(measurements);
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for (SensorDescriptor.Value valueDescriptor : valueDescriptors) {
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String name = getUniqueName(names, valueDescriptor);
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String deviceClass = getDeviceClass(valueDescriptor.getKind());
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if (deviceClass != null) {
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sb.append(" - name: \"").append(name).append("\"\n");
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sb.append(" value_template: \"{{ value_json['").append(name).append("'] }}\"\n");
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sb.append(" device_class: ").append(deviceClass).append("\n");
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sb.append(" unit_of_measurement: \"").append(getUnit(valueDescriptor.getKind())).append("\"\n");
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}
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}
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}
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return "text/vnd.yaml";
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}
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String renderHelp(StringBuilder sb) {
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sb.append("Pi4J I2C Autodetect Sensor Server\n\n");
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sb.append("HomeAssistant YAML\n");
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sb.append("configuration snippet: ").append(address).append("/config\n");
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sb.append("Measurements: ").append(address).append("/measurements\n");
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sb.append("This help text: ").append(address).append("\n");
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return "text/plain";
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}
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static String getDeviceClass(SensorDescriptor.Kind kind) {
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return switch(kind) {
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case LIGHT, LIGHT_BLUE, LIGHT_RED, LIGHT_GREEN -> "illuminance";
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case CO2, DISTANCE, HUMIDITY, PRESSURE, TEMPERATURE -> kind.name().toLowerCase(Locale.ROOT);
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default -> null;
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};
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}
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static String getUnit(SensorDescriptor.Kind kind) {
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return switch (kind) {
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case ACCELERATION_X, ACCELERATION_Y, ACCELERATION_Z -> "m/s²";
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case ANGULAR_VELOCITY_X, ANGULAR_VELOCITY_Y, ANGULAR_VELOCITY_Z -> "°/s";
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case CO2 -> "ppm";
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case DISTANCE -> "m";
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case HUMIDITY -> "%";
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case LIGHT, LIGHT_BLUE, LIGHT_RED, LIGHT_GREEN -> "lx";
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case MAGNETIC_FIELD_X, MAGNETIC_FIELD_Y, MAGNETIC_FIELD_Z -> "G";
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case PRESSURE -> "hPa";
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case TEMPERATURE -> "°C";
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};
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}
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static String getUniqueName(Map<String, Integer> names, SensorDescriptor.Value valueDescriptor) {
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String name = valueDescriptor.getKind().toString().toLowerCase(Locale.ROOT);
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int suffix = names.getOrDefault(name, 1);
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names.put(name, suffix + 1);
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return suffix > 1 ? name + "_" + suffix : name;
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}
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public static void main(String[] args) throws InterruptedException, IOException {
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Context pi4j = Pi4J.newAutoContext();
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List<Sensor> sensorList = SensorDetector.detectI2cSensors(pi4j, BUS);
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System.out.println("Detected sensors: " + sensorList.stream().map(s -> s.getClass().getSimpleName()).toList());
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System.out.println("Starting server on port " + PORT);
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System.out.println();
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SensorServer server = new SensorServer(PORT, sensorList);
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StringBuilder sb = new StringBuilder();
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server.renderHelp(sb);
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System.out.println(sb);
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server.run();
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}
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}

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