Bael 389 - Chat-like app using the Java API for WebSocket (#1265)

* Project for " A Guide to the Java API for WebSocket" article

* Setting dependencies correctly

* Formatting adjustments

* Removing tomcat7 maven plugin

* Applying formatt - No spaces

java-websocket/src/main/java/com/baeldung/model/Message.java

@@ -0,0 +1,36 @@
+package com.baeldung.model;
+
+public class Message {
+    private String from;
+    private String to;
+    private String content;
+
+    @Override
+    public String toString() {
+        return super.toString();
+    }
+
+    public String getFrom() {
+        return from;
+    }
+
+    public void setFrom(String from) {
+        this.from = from;
+    }
+
+    public String getTo() {
+        return to;
+    }
+
+    public void setTo(String to) {
+        this.to = to;
+    }
+
+    public String getContent() {
+        return content;
+    }
+
+    public void setContent(String content) {
+        this.content = content;
+    }
+}

java-websocket/src/main/java/com/baeldung/websocket/ChatEndpoint.java

@@ -0,0 +1,71 @@
+package com.baeldung.websocket;
+
+import java.io.IOException;
+import java.util.HashMap;
+import java.util.Set;
+import java.util.concurrent.CopyOnWriteArraySet;
+
+import javax.websocket.EncodeException;
+import javax.websocket.OnClose;
+import javax.websocket.OnError;
+import javax.websocket.OnMessage;
+import javax.websocket.OnOpen;
+import javax.websocket.Session;
+import javax.websocket.server.PathParam;
+import javax.websocket.server.ServerEndpoint;
+
+import com.baeldung.model.Message;
+
+@ServerEndpoint(value = "/chat/{username}", decoders = MessageDecoder.class, encoders = MessageEncoder.class)
+public class ChatEndpoint {
+    private Session session;
+    private static final Set<ChatEndpoint> chatEndpoints = new CopyOnWriteArraySet<>();
+    private static HashMap<String, String> users = new HashMap<>();
+
+    @OnOpen
+    public void onOpen(Session session, @PathParam("username") String username) throws IOException, EncodeException {
+
+        this.session = session;
+        chatEndpoints.add(this);
+        users.put(session.getId(), username);
+
+        Message message = new Message();
+        message.setFrom(username);
+        message.setContent("Connected!");
+        broadcast(message);
+    }
+
+    @OnMessage
+    public void onMessage(Session session, Message message) throws IOException, EncodeException {
+        message.setFrom(users.get(session.getId()));
+        broadcast(message);
+    }
+
+    @OnClose
+    public void onClose(Session session) throws IOException, EncodeException {
+        chatEndpoints.remove(this);
+        Message message = new Message();
+        message.setFrom(users.get(session.getId()));
+        message.setContent("Disconnected!");
+        broadcast(message);
+    }
+
+    @OnError
+    public void onError(Session session, Throwable throwable) {
+        // Do error handling here
+    }
+
+    private static void broadcast(Message message) throws IOException, EncodeException {
+        chatEndpoints.forEach(endpoint -> {
+            synchronized (endpoint) {
+                try {
+                    endpoint.session.getBasicRemote()
+                        .sendObject(message);
+                } catch (IOException | EncodeException e) {
+                    e.printStackTrace();
+                }
+            }
+        });
+    }
+
+}

java-websocket/src/main/java/com/baeldung/websocket/MessageDecoder.java

@@ -0,0 +1,32 @@
+package com.baeldung.websocket;
+
+import javax.websocket.DecodeException;
+import javax.websocket.Decoder;
+import javax.websocket.EndpointConfig;
+
+import com.baeldung.model.Message;
+import com.google.gson.Gson;
+
+public class MessageDecoder implements Decoder.Text<Message> {
+    @Override
+    public Message decode(String s) throws DecodeException {
+        Gson gson = new Gson();
+        Message message = gson.fromJson(s, Message.class);
+        return message;
+    }
+
+    @Override
+    public boolean willDecode(String s) {
+        return (s != null);
+    }
+
+    @Override
+    public void init(EndpointConfig endpointConfig) {
+        // Custom initialization logic
+    }
+
+    @Override
+    public void destroy() {
+        // Close resources
+    }
+}

java-websocket/src/main/java/com/baeldung/websocket/MessageEncoder.java

@@ -0,0 +1,27 @@
+package com.baeldung.websocket;
+
+import javax.websocket.EncodeException;
+import javax.websocket.Encoder;
+import javax.websocket.EndpointConfig;
+
+import com.baeldung.model.Message;
+import com.google.gson.Gson;
+
+public class MessageEncoder implements Encoder.Text<Message> {
+    @Override
+    public String encode(Message message) throws EncodeException {
+        Gson gson = new Gson();
+        String json = gson.toJson(message);
+        return json;
+    }
+
+    @Override
+    public void init(EndpointConfig endpointConfig) {
+        // Custom initialization logic
+    }
+
+    @Override
+    public void destroy() {
+        // Close resources
+    }
+}