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Improved serial port handling
By separated the connection management (connecting, reconnecting, and listening for disconnections) from command handling (sending data over the port) ConnectionManager: Handles connection and reconnection logic. This class listens for disconnection events and tries to reconnect based on exponential backoff. Event Notifications: It notifies listeners of disconnects and reconnects. Defined a ConnectionListener interface that notify on events such as disconnect and reconnect. CommandSender: Depends on ConnectionManager for the current connection state. It only sends commands if the port is connected. It listens for onReconnect events to resend the last command automatically after a reconnect.
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8 files changed

+187
-57
lines changed

8 files changed

+187
-57
lines changed

‎build.gradle‎

Lines changed: 5 additions & 5 deletions
Original file line numberDiff line numberDiff line change
@@ -8,24 +8,24 @@ application {
88
}
99

1010
group = 'org.senegas'
11-
version = '1.0.2'
11+
version = '1.1.0'
1212

1313
repositories {
1414
mavenCentral()
1515
}
1616

1717
dependencies {
18-
testImplementation platform('org.junit:junit-bom:5.9.1')
19-
testImplementation 'org.junit.jupiter:junit-jupiter'
20-
2118
// https://mvnrepository.com/artifact/com.fazecast/jSerialComm
22-
implementation group: 'com.fazecast', name: 'jSerialComm', version: '2.10.4'
19+
implementation group: 'com.fazecast', name: 'jSerialComm', version: '2.11.0'
2320

2421
// https://mvnrepository.com/artifact/com.formdev/flatlaf
2522
implementation group: 'com.formdev', name: 'flatlaf', version: '3.2.5'
2623

2724
// https://mvnrepository.com/artifact/com.miglayout/miglayout-swing
2825
implementation group: 'com.miglayout', name: 'miglayout-swing', version: '11.1'
26+
27+
testImplementation platform('org.junit:junit-bom:5.9.1')
28+
testImplementation 'org.junit.jupiter:junit-jupiter'
2929
}
3030

3131
test {

‎src/main/java/org/senegas/trafficlight/TrafficLightApp.java‎

Lines changed: 1 addition & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -18,7 +18,7 @@ public class TrafficLightApp {
1818
public static final String TITLE = "Traffic Light App";
1919
//TODO
2020
// // see https://stackoverflow.com/questions/33020069/how-to-get-version-attribute-from-a-gradle-build-to-be-included-in-runtime-swing
21-
public static final String VERSION = "1.0.2";
21+
public static final String VERSION = "1.1.0";
2222

2323
public static void main(String[] args) {
2424
EventQueue.invokeLater(() -> new TrafficLightApp().create());

‎src/main/java/org/senegas/trafficlight/serial/CommPort.java‎

Lines changed: 0 additions & 42 deletions
This file was deleted.

‎src/main/java/org/senegas/trafficlight/serial/CommPortSelector.java‎

Lines changed: 4 additions & 5 deletions
Original file line numberDiff line numberDiff line change
@@ -30,10 +30,9 @@ void dumpPorts() {
3030
}
3131
}
3232

33-
public CommPort select() throws CommPortException {
33+
public SerialPort select() throws CommPortException {
3434

3535
SerialPort[] commPorts = SerialPort.getCommPorts();
36-
3736
Optional<SerialPort> opt = Arrays.stream(commPorts)
3837
.filter(port -> port.getDescriptivePortName().contains("CH340"))
3938
.findFirst();
@@ -49,9 +48,9 @@ public CommPort select() throws CommPortException {
4948
throw new CommPortException("Could not find a connected Arduino");
5049
}
5150

52-
SerialPort port = opt.get();
53-
LOGGER.log(Level.INFO, "Arduino detected on port {0}", port.getSystemPortName());
51+
SerialPort serialPort = opt.get();
52+
LOGGER.log(Level.INFO, "Arduino detected on port {0}", serialPort.getSystemPortName());
5453

55-
return new CommPort(port);
54+
return serialPort;
5655
}
5756
}

‎src/main/java/org/senegas/trafficlight/serial/CommandSender.java‎

Lines changed: 47 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,47 @@
1+
package org.senegas.trafficlight.serial;
2+
3+
import java.util.logging.Level;
4+
import java.util.logging.Logger;
5+
6+
public class CommandSender implements ConnectionListener {
7+
private static final Logger LOGGER = Logger.getLogger(CommandSender.class.getName());
8+
9+
private final ConnectionManager connectionManager;
10+
private String lastSentCommand;
11+
12+
public CommandSender(ConnectionManager connectionManager) {
13+
this.connectionManager = connectionManager;
14+
connectionManager.addConnectionListener(this);
15+
}
16+
17+
public void send(String command) {
18+
if (connectionManager.isConnected()) {
19+
int written = connectionManager.getSerialPort().writeBytes((command + "\0").getBytes(), command.length() + 1);
20+
if (written == -1) {
21+
LOGGER.log(Level.SEVERE, "There was an error writing to the port.");
22+
}
23+
lastSentCommand = command;
24+
}
25+
26+
}
27+
28+
@Override
29+
public void onDisconnect() {
30+
LOGGER.log(Level.SEVERE, "Disconnected, will attempt to resend last command on reconnect.");
31+
}
32+
33+
@Override
34+
public void onReconnect() {
35+
if (lastSentCommand != null) {
36+
LOGGER.log(Level.INFO, "Resend last command after reconnect.");
37+
try {
38+
LOGGER.log(Level.INFO, "Wait seconds in case the Arduino board is booting...");
39+
Thread.sleep(10_000);
40+
send(lastSentCommand); // Resend last command after reconnect
41+
LOGGER.log(Level.INFO, "Last command resent.");
42+
} catch (InterruptedException e) {
43+
Thread.currentThread().interrupt();
44+
}
45+
}
46+
}
47+
}

‎src/main/java/org/senegas/trafficlight/serial/ConnectionListener.java‎

Lines changed: 6 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,6 @@
1+
package org.senegas.trafficlight.serial;
2+
3+
public interface ConnectionListener {
4+
void onDisconnect();
5+
void onReconnect();
6+
}

‎src/main/java/org/senegas/trafficlight/serial/ConnectionManager.java‎

Lines changed: 115 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,115 @@
1+
package org.senegas.trafficlight.serial;
2+
3+
import com.fazecast.jSerialComm.SerialPort;
4+
import com.fazecast.jSerialComm.SerialPortDataListener;
5+
import com.fazecast.jSerialComm.SerialPortEvent;
6+
7+
import java.io.ByteArrayOutputStream;
8+
import java.util.ArrayList;
9+
import java.util.List;
10+
import java.util.logging.Level;
11+
import java.util.logging.Logger;
12+
13+
public class ConnectionManager {
14+
15+
private static final Logger LOGGER = Logger.getLogger(ConnectionManager.class.getName());
16+
17+
private SerialPort serialPort;
18+
private final int BASE_RECONNECT_INTERVAL = 5000; // 5 seconds
19+
private final int MAX_RECONNECT_INTERVAL = 60000; // 1 minute
20+
private final int MAX_RETRIES = 10; // Max retry limit
21+
22+
private final List<ConnectionListener> listeners = new ArrayList<>();
23+
24+
public ConnectionManager(SerialPort jSerialPort) {
25+
this.serialPort = jSerialPort;
26+
27+
Runtime.getRuntime().addShutdownHook(new Thread(() -> {
28+
LOGGER.log(Level.INFO, "Closing port {0}...", jSerialPort.getSystemPortPath());
29+
boolean isPortClosed = jSerialPort.closePort();
30+
LOGGER.log(Level.INFO, "Closing port has {0}", (isPortClosed ? "been successful" : "failed"));
31+
}));
32+
33+
connect();
34+
}
35+
36+
public void addConnectionListener(ConnectionListener listener) {
37+
listeners.add(listener);
38+
}
39+
40+
private void notifyDisconnect() {
41+
for (ConnectionListener listener : listeners) {
42+
listener.onDisconnect();
43+
}
44+
}
45+
46+
private void notifyReconnect() {
47+
for (ConnectionListener listener : listeners) {
48+
listener.onReconnect();
49+
}
50+
}
51+
52+
public void connect() {
53+
if (serialPort.openPort()) {
54+
// https://fazecast.github.io/jSerialComm/javadoc/com/fazecast/jSerialComm/SerialPortDataListener.html
55+
// https://github.com/Fazecast/jSerialComm/wiki/Event-Based-Reading-Usage-Example
56+
serialPort.addDataListener(new SerialPortDataListener() {
57+
@Override
58+
public int getListeningEvents() {
59+
return SerialPort.LISTENING_EVENT_PORT_DISCONNECTED;
60+
}
61+
62+
@Override
63+
public void serialEvent(SerialPortEvent event) {
64+
switch (event.getEventType()) {
65+
// https://github.com/Fazecast/jSerialComm/wiki/Modes-of-Operation#for-port-disconnects
66+
case SerialPort.LISTENING_EVENT_PORT_DISCONNECTED:
67+
LOGGER.log(Level.INFO, "Port disconnected. Attempting to reconnect...");
68+
69+
handlePortDisconnection();
70+
break;
71+
}
72+
}
73+
});
74+
}
75+
}
76+
77+
public boolean isConnected() {
78+
return serialPort.isOpen();
79+
}
80+
81+
public SerialPort getSerialPort() {
82+
return this.serialPort;
83+
}
84+
85+
private void handlePortDisconnection() {
86+
serialPort.closePort();
87+
notifyDisconnect();
88+
int reconnectInterval = BASE_RECONNECT_INTERVAL;
89+
int attemptCount = 0;
90+
91+
while (! serialPort.isOpen() && attemptCount < MAX_RETRIES) {
92+
try {
93+
Thread.sleep(reconnectInterval);
94+
LOGGER.log(Level.INFO, "Attempting to reconnect...");
95+
if (serialPort.openPort()) {
96+
LOGGER.log(Level.INFO, "Reconnected successfully.");
97+
reconnectInterval = BASE_RECONNECT_INTERVAL; // Reset interval on success
98+
notifyReconnect();
99+
} else {
100+
reconnectInterval = Math.min(reconnectInterval * 2, MAX_RECONNECT_INTERVAL); // Exponential backoff
101+
LOGGER.log(Level.INFO, "Reconnection failed. Next attempt in " + reconnectInterval / 1000 + " seconds.");
102+
}
103+
} catch (InterruptedException e) {
104+
Thread.currentThread().interrupt();
105+
LOGGER.log(Level.SEVERE, "Reconnect attempt interrupted.", e);
106+
break;
107+
}
108+
attemptCount++;
109+
}
110+
111+
if (! serialPort.isOpen()) {
112+
LOGGER.log(Level.SEVERE, "Failed to reconnect after " + MAX_RETRIES + " attempts.");
113+
}
114+
}
115+
}

‎src/main/java/org/senegas/trafficlight/view/SerialMessageEmitter.java‎

Lines changed: 9 additions & 4 deletions
Original file line numberDiff line numberDiff line change
@@ -1,7 +1,9 @@
11
package org.senegas.trafficlight.view;
22

3+
import com.fazecast.jSerialComm.SerialPort;
34
import org.senegas.trafficlight.model.TrafficLightModel;
4-
import org.senegas.trafficlight.serial.CommPort;
5+
import org.senegas.trafficlight.serial.CommandSender;
6+
import org.senegas.trafficlight.serial.ConnectionManager;
57
import org.senegas.trafficlight.serial.CommPortException;
68
import org.senegas.trafficlight.serial.CommPortSelector;
79

@@ -13,7 +15,7 @@
1315
public class SerialMessageEmitter implements PropertyChangeListener {
1416
private static final Logger LOGGER = Logger.getLogger(SerialMessageEmitter.class.getName());
1517
private TrafficLightModel model;
16-
private CommPort port;
18+
private CommandSender commandSender;
1719

1820
public SerialMessageEmitter() {
1921
initSerialPort();
@@ -27,12 +29,15 @@ public void setModel(TrafficLightModel model) {
2729

2830
@Override
2931
public void propertyChange(PropertyChangeEvent evt) {
30-
this.port.send(this.model.toArduinoCommand());
32+
this.commandSender.send(this.model.toArduinoCommand());
3133
}
3234

3335
private void initSerialPort() {
3436
try {
35-
this.port = CommPortSelector.INSTANCE.select();
37+
SerialPort serialPort = CommPortSelector.INSTANCE.select();
38+
serialPort.setBaudRate(9600); // Set as needed
39+
40+
this.commandSender = new CommandSender(new ConnectionManager(serialPort));
3641
} catch (CommPortException e) {
3742
LOGGER.log(Level.SEVERE, e.getMessage());
3843
}

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