var socket = new WebSocket('ws://' + window.location.host + '/my-websocket-endpoint');
 
// Add an event listener for when a connection is open
socket.onopen = function() {
 console.log('WebSocket connection opened. Ready to send messages.');
 
 // Send a message to the server
 socket.send('Hello, from WebSocket client!');
};
 
// Add an event listener for when a message is received from the server
socket.onmessage = function(message) {
 console.log('Message received from server: ' + message);
};

public class MyMessageHandler extends TextWebSocketHandler {
 
  @Override
  public void afterConnectionClosed(WebSocketSession session, CloseStatus status) throws Exception {
    // The WebSocket has been closed
  }
 
  @Override
  public void afterConnectionEstablished(WebSocketSession session) throws Exception {
    // The WebSocket has been opened
    // I might save this session object so that I can send messages to it outside of this method
 
    // Let's send the first message
    session.sendMessage(new TextMessage("You are now connected to the server. This is the first message."));
  }
 
  @Override
  protected void handleTextMessage(WebSocketSession session, TextMessage textMessage) throws Exception {
    // A message has been received
    System.out.println("Message received: " + textMessage.getPayload());
  }
}

@Configuration
@EnableWebSocket
public class WebsocketConfig implements WebSocketConfigurer {
 
  @Bean
  public WebSocketHandler myMessageHandler() {
    return new MyMessageHandler();
  }
 
  @Override
  public void registerWebSocketHandlers(WebSocketHandlerRegistry registry) {
    registry.addHandler(myMessageHandler(), "/my-websocket-endpoint");
  }
 
}