WebSocket API

pandalib-util/src/main/java/fr/pandacube/lib/util/ThrowableUtil.java

@@ -96,9 +96,14 @@ public class ThrowableUtil {
 	}
 
 
-
-
-	private static RuntimeException uncheck(Throwable t, boolean convertReflectionExceptionToError) {
+	/**
+	 * Makes the provided Throwable unckecked if necessary.
+	 * @param t the throwable to eventually wrap into a {@link RuntimeException}.
+	 * @param convertReflectionExceptionToError true to convert reflection related exception to their error counterpart.
+	 * @return a {@link RuntimeException}
+	 * @throws Error if one is passed as the parameter.
+	 */
+	public static RuntimeException uncheck(Throwable t, boolean convertReflectionExceptionToError) {
 		if (t instanceof Error er) {
 			throw er;
 		}

pandalib-ws-client/pom.xml

@@ -0,0 +1,24 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.0.0"
+         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <parent>
+        <artifactId>pandalib-parent</artifactId>
+        <groupId>fr.pandacube.lib</groupId>
+        <version>1.0-SNAPSHOT</version>
+        <relativePath>../pom.xml</relativePath>
+    </parent>
+    <modelVersion>4.0.0</modelVersion>
+
+    <artifactId>pandalib-ws-client</artifactId>
+    <packaging>jar</packaging>
+
+    <dependencies>
+        <dependency>
+            <groupId>fr.pandacube.lib</groupId>
+            <artifactId>pandalib-ws</artifactId>
+            <version>${project.version}</version>
+        </dependency>
+    </dependencies>
+
+</project>

pandalib-ws-client/src/main/java/fr/pandacube/lib/ws/client/AbstractClientWS.java

@@ -0,0 +1,117 @@
+package fr.pandacube.lib.ws.client;
+
+import fr.pandacube.lib.util.Log;
+import fr.pandacube.lib.util.ThrowableUtil;
+import fr.pandacube.lib.ws.AbstractWS;
+
+import java.io.IOException;
+import java.net.URI;
+import java.net.URISyntaxException;
+import java.net.http.HttpClient;
+import java.net.http.WebSocket;
+import java.net.http.WebSocket.Listener;
+import java.nio.ByteBuffer;
+import java.time.Duration;
+import java.util.concurrent.CompletionException;
+import java.util.concurrent.CompletionStage;
+import java.util.concurrent.atomic.AtomicReference;
+
+// TODO implement auto-reconnect
+/**
+ * Minimal implementation of a Websocket client endpoint using the java.net.http Websocket API.
+ */
+public abstract class AbstractClientWS implements AbstractWS {
+
+    private final URI uri;
+    private boolean autoReconnect;
+    private final AtomicReference<WebSocket> socket = new AtomicReference<>();
+
+
+    private final Listener receiveListener = new Listener() {
+        @Override
+        public void onOpen(WebSocket webSocket) {
+            AbstractClientWS.this.onConnect();
+            Listener.super.onOpen(webSocket);
+        }
+
+        @Override
+        public CompletionStage<?> onText(WebSocket webSocket, CharSequence data, boolean last) {
+            AbstractClientWS.this.handleReceivedMessage(data.toString());
+            return Listener.super.onText(webSocket, data, last);
+        }
+
+        @Override
+        public CompletionStage<?> onBinary(WebSocket webSocket, ByteBuffer data, boolean last) {
+            AbstractClientWS.this.handleReceivedBinary();
+            return Listener.super.onBinary(webSocket, data, last);
+        }
+
+        @Override
+        public CompletionStage<?> onClose(WebSocket webSocket, int statusCode, String reason) {
+            AbstractClientWS.this.onClose(statusCode, reason);
+            return Listener.super.onClose(webSocket, statusCode, reason);
+        }
+
+        @Override
+        public void onError(WebSocket webSocket, Throwable error) {
+            AbstractClientWS.this.onError(error);
+            Listener.super.onError(webSocket, error);
+        }
+    };
+
+
+    /**
+     * Creates a new Websocket client that connect to the provided url.
+     * @param uri the destination endpoint.
+     * @param autoReconnect if this websocket should automatically try to reconnect when disconnected.
+     * @throws URISyntaxException if the provided URI is invalid.
+     */
+    public AbstractClientWS(String uri, boolean autoReconnect) throws URISyntaxException {
+        this.uri = new URI(uri);
+        this.autoReconnect = autoReconnect;
+        if (autoReconnect) {
+            Log.warning("Websocket client auto-reconnect is not yet implemented.");
+        }
+        connect();
+    }
+
+
+    private void connect() {
+        synchronized (socket) {
+            socket.set(HttpClient.newHttpClient()
+                    .newWebSocketBuilder()
+                    .connectTimeout(Duration.ofSeconds(2))
+                    .buildAsync(uri, receiveListener)
+                    .join()
+            );
+        }
+    }
+
+
+    @Override
+    public final void sendString(String message) throws IOException {
+        try {
+            synchronized (socket) {
+                socket.get().sendText(message, true).join();
+            }
+        } catch (CompletionException ce) {
+            if (ce.getCause() instanceof IOException ioe)
+                throw ioe;
+            throw ThrowableUtil.uncheck(ce.getCause(), false);
+        }
+    }
+
+    @Override
+    public String getRemoteIdentifier() {
+        return uri.toString();
+    }
+
+    @Override
+    public final void sendClose(int code, String reason) throws IOException {
+        synchronized (socket) {
+            autoReconnect = false; // if we ask for closing connection, dont reconnect automatically
+            socket.get().sendClose(code, reason);
+        }
+    }
+
+}

pandalib-ws-client/src/main/java/fr/pandacube/lib/ws/client/KeyProtectedClientWS.java

@@ -0,0 +1,97 @@
+package fr.pandacube.lib.ws.client;
+
+import fr.pandacube.lib.ws.payloads.ErrorPayload;
+import fr.pandacube.lib.ws.payloads.LoginPayload;
+import fr.pandacube.lib.ws.payloads.LoginSucceedPayload;
+import fr.pandacube.lib.ws.payloads.Payload;
+
+import java.net.URISyntaxException;
+
+/**
+ * Websocket client that implements the login logic with a key protected server endpoint.
+ */
+public abstract class KeyProtectedClientWS extends AbstractClientWS {
+
+    private final String key;
+
+    private boolean loginSucceed = false;
+
+    /**
+     * Creates a new Websocket client that connect to the provided url and uses the provided key.
+     * @param uri the destination endpoint.
+     * @param autoReconnect if this websocket should automatically try to reconnect when disconnected.
+     * @param key the login key.
+     * @throws URISyntaxException if the provided URI is invalid.
+     */
+    public KeyProtectedClientWS(String uri, boolean autoReconnect, String key) throws URISyntaxException {
+        super(uri, autoReconnect);
+        this.key = key;
+    }
+
+
+    @Override
+    public final void onConnect() {
+        trySendAsJson(new LoginPayload(key));
+    }
+
+    @Override
+    public final void onReceivePayload(Payload payload) {
+        if (loginSucceed) {
+            onReceivePayloadLoggedIn(payload);
+        }
+        else if (payload instanceof LoginSucceedPayload) {
+            loginSucceed = true;
+            onLoginSucceed();
+        }
+        else if (payload instanceof ErrorPayload err){
+            logError("Received ErrorPayload instead of LoginSuccessPayload: " + err.message, err.throwable);
+            trySendClose();
+        }
+        else {
+            logError("Received unexpected Payload instead of LoginSuccessPayload: " + payload.getClass().getSimpleName());
+            trySendClose();
+        }
+    }
+
+    @Override
+    public final void onClose(int code, String reason) {
+        if (loginSucceed) {
+            loginSucceed = false;
+            onCloseLoggedIn(code, reason);
+        }
+    }
+
+    @Override
+    public final void onError(Throwable cause) {
+        if (loginSucceed) {
+            loginSucceed = false;
+            onErrorLoggedIn(cause);
+        }
+    }
+
+    /**
+     * Called when this Websocket is succesfully logged in to the server.
+     */
+    public abstract void onLoginSucceed();
+
+    /**
+     * Called on reception of a valid payload when already logged in.
+     * @param payload the received payload.
+     */
+    public abstract void onReceivePayloadLoggedIn(Payload payload);
+
+    /**
+     * Called on reception of a websocket Close packet, only if this client is already logged in.
+     * The connection is closed after this method call.
+     * @param code the close code. 1000 for a normal closure.
+     * @param reason the close reason.
+     */
+    public abstract void onCloseLoggedIn(int code, String reason);
+
+    /**
+     * Called when an error occurs with the websocket API, only if this client is already logged in.
+     * The connection is already closed when this method is called.
+     * @param cause the error cause.
+     */
+    public abstract void onErrorLoggedIn(Throwable cause);
+}

pandalib-ws-server/pom.xml

@@ -0,0 +1,29 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.0.0"
+         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <parent>
+        <artifactId>pandalib-parent</artifactId>
+        <groupId>fr.pandacube.lib</groupId>
+        <version>1.0-SNAPSHOT</version>
+        <relativePath>../pom.xml</relativePath>
+    </parent>
+    <modelVersion>4.0.0</modelVersion>
+
+    <artifactId>pandalib-ws-server</artifactId>
+    <packaging>jar</packaging>
+
+    <dependencies>
+        <dependency>
+            <groupId>fr.pandacube.lib</groupId>
+            <artifactId>pandalib-ws</artifactId>
+            <version>${project.version}</version>
+        </dependency>
+        <dependency>
+            <groupId>org.eclipse.jetty.websocket</groupId>
+            <artifactId>websocket-jetty-api</artifactId>
+            <version>10.0.5</version>
+        </dependency>
+    </dependencies>
+
+</project>

pandalib-ws-server/src/main/java/fr/pandacube/lib/ws/server/AbstractServerWS.java

@@ -0,0 +1,60 @@
+package fr.pandacube.lib.ws.server;
+
+import fr.pandacube.lib.ws.AbstractWS;
+import org.eclipse.jetty.websocket.api.Session;
+import org.eclipse.jetty.websocket.api.WebSocketAdapter;
+
+import java.io.IOException;
+
+/**
+ * Minimal implementation of a Websocket server endpoint using the Jetty Websocket API.
+ */
+public abstract class AbstractServerWS extends WebSocketAdapter implements AbstractWS {
+	
+	@Override
+	public final void onWebSocketConnect(Session sess)
+	{
+		super.onWebSocketConnect(sess);
+		onConnect();
+	}
+
+	@Override
+	public final void onWebSocketBinary(byte[] payload, int offset, int len) {
+		handleReceivedBinary();
+	}
+
+	@Override
+	public final void onWebSocketText(String message) {
+		handleReceivedMessage(message);
+	}
+
+	@Override
+	public final void onWebSocketClose(int statusCode, String reason) {
+		onClose(statusCode, reason);
+	}
+
+	@Override
+	public final void onWebSocketError(Throwable cause) {
+		onError(cause);
+	}
+
+
+
+
+
+
+
+	public final void sendString(String message) throws IOException {
+		getSession().getRemote().sendString(message);
+	}
+
+	@Override
+	public final void sendClose(int code, String reason) throws IOException {
+		getSession().close(code, reason);
+	}
+
+	@Override
+	public String getRemoteIdentifier() {
+		return getSession().getRemoteAddress().toString();
+	}
+}

pandalib-ws-server/src/main/java/fr/pandacube/lib/ws/server/KeyProtectedServerWS.java

@@ -0,0 +1,95 @@
+package fr.pandacube.lib.ws.server;
+
+import fr.pandacube.lib.ws.payloads.ErrorPayload;
+import fr.pandacube.lib.ws.payloads.LoginPayload;
+import fr.pandacube.lib.ws.payloads.LoginSucceedPayload;
+import fr.pandacube.lib.ws.payloads.Payload;
+
+import java.util.function.Supplier;
+
+/**
+ * Websocket server endpoint that is protected with a key.
+ */
+public abstract class KeyProtectedServerWS extends AbstractServerWS {
+
+	private boolean loginSucceed = false;
+
+	private final Supplier<String> keySupplier;
+
+	/**
+	 * Creates a websocket server endpoint protected by the key given by the provided {@link Supplier}.
+	 * @param keySupplier a {@link Supplier} for the key.
+	 */
+	public KeyProtectedServerWS(Supplier<String> keySupplier) {
+		this.keySupplier = keySupplier;
+	}
+
+	@Override
+	public final void onConnect() {
+		// nothing, just wait for the client to login
+	}
+
+	@Override
+	public final void onReceivePayload(Payload payload) {
+		if (loginSucceed) {
+			onReceivePayloadLoggedIn(payload);
+		}
+		else if (payload instanceof LoginPayload login) {
+			if (keySupplier.get().equals(login.key)) {
+				loginSucceed = true;
+				trySendAsJson(new LoginSucceedPayload());
+				onLoginSucceed();
+			}
+			else {
+				logAndTrySendError(new ErrorPayload("Bad key"));
+				trySendClose();
+			}
+		}
+		else {
+			logAndTrySendError(new ErrorPayload("Please use the login packet first. Received " + payload.getClass().getSimpleName() + " instead."));
+			trySendClose();
+		}
+	}
+
+	@Override
+	public final void onClose(int code, String reason) {
+		if (loginSucceed) {
+			onCloseLoggedIn(code, reason);
+		}
+	}
+
+	@Override
+	public final void onError(Throwable cause) {
+		if (loginSucceed) {
+			onErrorLoggedIn(cause);
+		}
+	}
+
+	/**
+	 * Called when the client endpoint is succesfully logged in.
+	 */
+	public abstract void onLoginSucceed();
+
+	/**
+	 * Called on reception of a valid payload from the already logged in client.
+	 * @param payload the received payload.
+	 */
+	public abstract void onReceivePayloadLoggedIn(Payload payload);
+
+	/**
+	 * Called on reception of a websocket Close packet, only if the client endpoint is already logged in.
+	 * The connection is closed after this method call.
+	 * @param code the close code. 1000 for a normal closure.
+	 * @param reason the close reason.
+	 */
+	public abstract void onCloseLoggedIn(int code, String reason);
+
+	/**
+	 * Called when an error occurs with the websocket API, only if the client endpoint is already logged in.
+	 * The connection is already closed when this method is called.
+	 * @param cause the error cause.
+	 */
+	public abstract void onErrorLoggedIn(Throwable cause);
+
+
+}

pandalib-ws/pom.xml

@@ -0,0 +1,24 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.0.0"
+         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <parent>
+        <artifactId>pandalib-parent</artifactId>
+        <groupId>fr.pandacube.lib</groupId>
+        <version>1.0-SNAPSHOT</version>
+        <relativePath>../pom.xml</relativePath>
+    </parent>
+    <modelVersion>4.0.0</modelVersion>
+
+    <artifactId>pandalib-ws</artifactId>
+    <packaging>jar</packaging>
+
+    <dependencies>
+        <dependency>
+            <groupId>fr.pandacube.lib</groupId>
+            <artifactId>pandalib-core</artifactId>
+            <version>${project.version}</version>
+        </dependency>
+    </dependencies>
+
+</project>

pandalib-ws/src/main/java/fr/pandacube/lib/ws/AbstractWS.java

@@ -0,0 +1,257 @@
+package fr.pandacube.lib.ws;
+
+import fr.pandacube.lib.util.Log;
+import fr.pandacube.lib.util.ThrowableUtil.RunnableException;
+import fr.pandacube.lib.ws.payloads.ErrorPayload;
+import fr.pandacube.lib.ws.payloads.Payload;
+
+import java.io.IOException;
+import java.util.logging.Level;
+
+/**
+ * Super interface for all websocket endpoint, either client or server, that provides minimal implementation of our
+ * custom sub-protocol.
+ */
+public interface AbstractWS {
+
+    /*
+     * Receiving
+     */
+
+    /**
+     * Handles the reception of a message, by deserializing the payloads and handling eventual deserialization errors.
+     * @param message the raw message received.
+     */
+    default void handleReceivedMessage(String message) {
+        Payload payload;
+        try {
+            payload = PayloadRegistry.fromString(message);
+        } catch (IllegalArgumentException e) {
+            logAndTrySendError(new ErrorPayload(e.getMessage())); // no need to log or send full exception stack trace
+            return;
+        }
+
+        try {
+            onReceivePayload(payload);
+        } catch (Throwable t) {
+            trySendAsJson(new ErrorPayload("Error handling payload: " + t));
+            if (t instanceof Exception)
+                logError("Error handling payload", t);
+            else
+                throw t;
+        }
+    }
+
+    /**
+     * Handles the reception of binary data. The default implementation reject any binary data by sending an
+     * {@link ErrorPayload} to the remote endpoint.
+     */
+    default void handleReceivedBinary() {
+        trySendAsJson(new ErrorPayload("Cannot accept binary payload."));
+    }
+
+    /**
+     * Called when the websocket connection is established.
+     */
+    void onConnect();
+
+    /**
+     * Called on reception of a valid {@link Payload}.
+     * @param payload the received {@link Payload}.
+     */
+    void onReceivePayload(Payload payload);
+
+    /**
+     * Called on reception of a websocket Close packet.
+     * The connection is closed after this method call.
+     * @param code the close code. 1000 for a normal closure.
+     * @param reason the close reason.
+     */
+    void onClose(int code, String reason);
+
+    /**
+     * Called when an error occurs with the websocket API.
+     * The connection is already closed when this method is called.
+     * @param cause the error cause.
+     */
+    void onError(Throwable cause);
+
+
+
+
+
+
+
+
+    /*
+     * Sending
+     */
+
+    /**
+     * Send the provided raw string to the remote endpoint.
+     * <p>
+     * <b>It is not advised for subclasses to call directly this method.
+     * Please use {@link #sendAsJson(Payload)} or {@link #sendAsJson(String, Object, boolean)} instead.</b>
+     * @param message the raw message to send.
+     * @throws IOException if an IO error occurs when sending the message.
+     */
+    void sendString(String message) throws IOException;
+
+    /**
+     * Send the provided type and object that will be serialized using
+     * {@link PayloadRegistry#arbitraryToString(String, Object, boolean)}.
+     * @param type the type.
+     * @param obj the object to Jsonify.
+     * @param serializeNulls if null propreties must be included in the json object.
+     * @throws IOException if an IO error occurs when sending the data.
+     * @see PayloadRegistry#arbitraryToString(String, Object, boolean)
+     */
+    default void sendAsJson(String type, Object obj, boolean serializeNulls) throws IOException {
+        sendString(PayloadRegistry.arbitraryToString(type, obj, serializeNulls));
+    }
+
+    /**
+     * Send the provided type and object that will be serialized using
+     * {@link PayloadRegistry#arbitraryToString(String, Object, boolean)}.
+     * @param type the type.
+     * @param obj the object to Jsonify.
+     * @param serializeNulls if null propreties must be included in the json object.
+     * @return true if the data is sent successfully, false if an IO error occurs.
+     * @see PayloadRegistry#arbitraryToString(String, Object, boolean)
+     */
+    default boolean trySendAsJson(String type, Object obj, boolean serializeNulls) {
+        return trySend(() -> sendAsJson(type, obj, serializeNulls), "Error sending object as json");
+    }
+
+    /**
+     * Send the provided {@link Payload} to the remote endpoint.
+     * @param payload the {@link Payload} to send.
+     * @throws IOException if an IO error occurs when sending the data.
+     * @see PayloadRegistry#toString(Payload)
+     */
+    default void sendAsJson(Payload payload) throws IOException {
+        sendString(PayloadRegistry.toString(payload));
+    }
+
+    /**
+     * Send the provided {@link Payload} to the remote endpoint.
+     * @param payload the {@link Payload} to send.
+     * @return true if the data is sent successfully, false if an IO error occurs.
+     * @see PayloadRegistry#toString(Payload)
+     */
+    default boolean trySendAsJson(Payload payload) {
+        return trySend(() -> sendAsJson(payload), "Error sending payload as json");
+    }
+
+    /**
+     * Gracefully closes the connection by sending the close packet with the provided data.
+     * @param code the status code.
+     * @param reason the reason.
+     * @throws IOException if an IO error occurs when sending the close packet.
+     */
+    void sendClose(int code, String reason) throws IOException;
+
+    /**
+     * Gracefully closes the connection by sending the close packet with the provided data.
+     * @param code the status code.
+     * @param reason the reason.
+     * @return true if the data is sent successfully, false if an IO error occurs.
+     */
+    default boolean trySendClose(int code, String reason) {
+        return trySend(() -> sendClose(code, reason), "Error sending close");
+    }
+
+    /**
+     * Gracefully closes the connection by sending the close packet with the default status code (1000) and an empty
+     * reason.
+     * @throws IOException if an IO error occurs when sending the close packet.
+     */
+    default void sendClose() throws IOException {
+        sendClose(1000, "");
+    }
+
+    /**
+     * Gracefully closes the connection by sending the close packet with the default status code (1000) and an empty
+     * reason.
+     * @return true if the data is sent successfully, false if an IO error occurs.
+     */
+    default boolean trySendClose() {
+        return trySend(this::sendClose, "Error sending close");
+    }
+
+    /**
+     * Logs the error from the provided {@link ErrorPayload} and sends it to the remote endpoint.
+     * @param p the {@link ErrorPayload}.
+     * @throws IOException if an IO error occurs when sending the data.
+     */
+    default void logAndSendError(ErrorPayload p) throws IOException {
+        logError(p.message, p.throwable);
+        sendAsJson(p);
+    }
+
+    /**
+     * Logs the error from the provided {@link ErrorPayload} and sends it to the remote endpoint.
+     * @param p the {@link ErrorPayload}.
+     * @return true if the data is sent successfully, false if an IO error occurs.
+     */
+    default boolean logAndTrySendError(ErrorPayload p) {
+        return trySend(() -> logAndSendError(p), "Error sending error payload as json");
+    }
+
+    /**
+     * Utility method to wrap sending operation into a try-catch.
+     * @param run the sending operation that may throw an {@link IOException}.
+     * @param errorMessage the error message to log if the runnable throws an {@link IOException}.
+     * @return true if the data if the runnable is executed successfully, false if an IO error occurs.
+     */
+    default boolean trySend(RunnableException<IOException> run, String errorMessage) {
+        try {
+            run.run();
+            return true;
+        } catch (IOException e) {
+            logError(errorMessage, e);
+            return false;
+        }
+    }
+
+
+
+    /*
+     * Log
+     */
+
+    /**
+     * Logs the provided message with logger level {@link Level#INFO}, prefixed with infos avout this web-socket.
+     * @param message the message to log.
+     */
+    default void log(String message) {
+        Log.info(formatLogMessage(message));
+    }
+
+    /**
+     * Logs the provided message with logger level {@link Level#SEVERE}, prefixed with infos avout this web-socket.
+     * @param message the message to log.
+     */
+    default void logError(String message) {
+        logError(message, null);
+    }
+
+    /**
+     * Logs the provided message and {@link Throwable} with logger level {@link Level#SEVERE}, prefixed with infos avout this web-socket.
+     * @param message the message to log.
+     * @param t the throwable to log.
+     */
+    default void logError(String message, Throwable t) {
+        Log.severe(formatLogMessage(message), t);
+    }
+
+    /**
+     * Gets an identifier for this web-socket, used for logging. May be the remote IP:port or URI.
+     * @return an identifier for this web-socket.
+     */
+    String getRemoteIdentifier();
+
+    private String formatLogMessage(String message) {
+        return "[WS/" + getClass().getSimpleName() + "] [" + getRemoteIdentifier() + "] " + message;
+    }
+}

pandalib-ws/src/main/java/fr/pandacube/lib/ws/PayloadRegistry.java

@@ -0,0 +1,101 @@
+package fr.pandacube.lib.ws;
+
+import com.google.gson.JsonParseException;
+import fr.pandacube.lib.core.json.Json;
+import fr.pandacube.lib.util.BiMap;
+import fr.pandacube.lib.ws.payloads.ErrorPayload;
+import fr.pandacube.lib.ws.payloads.LoginPayload;
+import fr.pandacube.lib.ws.payloads.LoginSucceedPayload;
+import fr.pandacube.lib.ws.payloads.MessagePayload;
+import fr.pandacube.lib.ws.payloads.Payload;
+
+import java.util.regex.Pattern;
+
+/**
+ * Handles the registration of all the {@link Payload} types, the serialization and deserialization of the payload data.
+ */
+public class PayloadRegistry {
+
+    private static final String PAYLOAD_TYPE_SEPARATOR = ":";
+
+    private static final BiMap<String, Class<? extends Payload>> payloadClasses = new BiMap<>();
+
+
+    private static boolean isTypeValid(String type) {
+        return !type.contains(PAYLOAD_TYPE_SEPARATOR);
+    }
+
+    private static String validateType(String type) {
+        if (isTypeValid(type))
+            return type;
+        throw new IllegalArgumentException("Invalid characters in type identifier '" + type + "'");
+    }
+
+    /**
+     * Register a new {@link Payload} type.
+     * @param type the id of the payload type.
+     * @param clazz the payload class to register.
+     */
+    public static void registerPayloadType(String type, Class<? extends Payload> clazz) {
+        payloadClasses.put(validateType(type), clazz);
+    }
+
+    /**
+     * Deserialize the provided String into a valid Payload.
+     * @param message the serialized data.
+     * @return the {@link Payload}.
+     * @throws IllegalArgumentException if the serialized data does not have the proper format.
+     */
+    public static Payload fromString(String message) {
+        String[] split = message.split(Pattern.quote(PAYLOAD_TYPE_SEPARATOR), 2);
+        if (split.length != 2) {
+            throw new IllegalArgumentException("Malformed message: does not respect format '<type>" + PAYLOAD_TYPE_SEPARATOR + "<jsonObject>'.");
+        }
+
+        Class<? extends Payload> detectedClass = payloadClasses.get(split[0]);
+        if (detectedClass == null) {
+            throw new IllegalArgumentException("Unrecognized data type '" + split[0] + "'.");
+        }
+
+        try {
+            return Json.gson.fromJson(split[1], detectedClass);
+        } catch (JsonParseException e) {
+            throw new IllegalArgumentException(e.toString());
+        }
+    }
+
+    /**
+     * Serialize the provided {@link Payload}.
+     * @param p the {@link Payload} to serialize. Must be of a registered type.
+     * @return the serialized data.
+     */
+    public static String toString(Payload p) {
+        String type = payloadClasses.getKey(p.getClass());
+        if (type == null)
+            throw new IllegalArgumentException(p.getClass() + " is not a registered payload type.");
+        return arbitraryToString(type, p, false);
+    }
+
+
+    /**
+     * Serialize the provided arbitrary data, that consist of a type and an object that will be converted
+     * to a Json string.
+     * @param type the type
+     * @param obj the object to Jsonify
+     * @param serializeNulls if null propreties must be included in the json object.
+     * @return the String to send through the websocket
+     */
+    public static String arbitraryToString(String type, Object obj, boolean serializeNulls) {
+        return validateType(type) + PAYLOAD_TYPE_SEPARATOR + (serializeNulls ? Json.gsonSerializeNulls : Json.gson).toJson(obj);
+    }
+
+
+
+    static {
+        registerPayloadType("error", ErrorPayload.class);
+        registerPayloadType("message", MessagePayload.class);
+        registerPayloadType("login", LoginPayload.class);
+        registerPayloadType("login-succeed", LoginSucceedPayload.class);
+    }
+
+}

pandalib-ws/src/main/java/fr/pandacube/lib/ws/payloads/ErrorPayload.java

@@ -0,0 +1,36 @@
+package fr.pandacube.lib.ws.payloads;
+
+/**
+ * Error message payload.
+ */
+public class ErrorPayload extends Payload {
+    /**
+     * The error message.
+     */
+    public String message;
+    /**
+     * The error Throwable, may be null.
+     */
+    public Throwable throwable;
+
+    /**
+     * Initialize an error payload with a message but not throwable.
+     * @param message the error message.
+     */
+    public ErrorPayload(String message) {
+        this(message, null);
+    }
+
+    /**
+     * Initialize an error payload with a message and a throwable.
+     * @param message the error message.
+     * @param throwable the error Throwable, may be null.
+     */
+    public ErrorPayload(String message, Throwable throwable) {
+        this.message = message;
+        this.throwable = throwable;
+    }
+
+    @SuppressWarnings("unused")
+    private ErrorPayload() { } // for Json deserialization
+}

pandalib-ws/src/main/java/fr/pandacube/lib/ws/payloads/LoginPayload.java

@@ -0,0 +1,22 @@
+package fr.pandacube.lib.ws.payloads;
+
+/**
+ * Payload used by the client to login to key-protected websocket endpoint.
+ */
+public class LoginPayload extends Payload {
+    /**
+     * The key to use for login.
+     */
+    public String key;
+
+    /**
+     * Create a new LoginPayload with the provided key.
+     * @param key the key to use for login.
+     */
+    public LoginPayload(String key) {
+        this.key = key;
+    }
+
+    @SuppressWarnings("unused")
+    private LoginPayload() { } // for Json deserialization
+}

pandalib-ws/src/main/java/fr/pandacube/lib/ws/payloads/LoginSucceedPayload.java

@@ -0,0 +1,7 @@
+package fr.pandacube.lib.ws.payloads;
+
+/**
+ * Payload used by the server in inform the client the login was successfull.
+ */
+public class LoginSucceedPayload extends Payload {
+}

pandalib-ws/src/main/java/fr/pandacube/lib/ws/payloads/MessagePayload.java

@@ -0,0 +1,22 @@
+package fr.pandacube.lib.ws.payloads;
+
+/**
+ * A general use message Payload.
+ */
+public class MessagePayload extends Payload {
+    /**
+     * The message.
+     */
+    public String message;
+
+    /**
+     * Initialite a new MessagePayload with the provided message.
+     * @param message the message.
+     */
+    public MessagePayload(String message) {
+        this.message = message;
+    }
+
+    @SuppressWarnings("unused")
+    private MessagePayload() { } // for Json deserialization
+}

pandalib-ws/src/main/java/fr/pandacube/lib/ws/payloads/Payload.java

@@ -0,0 +1,8 @@
+package fr.pandacube.lib.ws.payloads;
+
+/**
+ * Superclass of all payload sent through our websockets.
+ */
+public abstract class Payload {
+
+}

pom.xml

@@ -77,6 +77,9 @@
         <module>pandalib-players-permissible</module>
         <module>pandalib-reflect</module>
         <module>pandalib-util</module>
+        <module>pandalib-ws</module>
+        <module>pandalib-ws-client</module>
+        <module>pandalib-ws-server</module>
     </modules>
 
     <dependencies>