The WebSocketConfigurer interface is used to map the handler with its specific URL in the registerWebSocketHandlers() method, as shown in the following code:

@Configuration 
@EnableWebSocket 
public class WebSocketConfig implements WebSocketConfigurer { 
  @Override 
  public void registerWebSocketHandlers(WebSocketHandlerRegistry   
    registry)  
  { 
    registry.addHandler(createHandler(), "/webSocketHandler"); 
  } 
  @Bean 
  public WebSocketHandler createMyHandler() { 
    return new MyWebSocketHandler(); 
  } 
} 

Here, our WebSocketHandler interface is mapped to the /webSocketHandler URL.

The customization of WebSocketHandler for the handshake can be done as follows:

@Configuration 
@EnableWebSocket 
public class MyWebSocketConfig implements WebSocketConfigurer { 
  @Override 
  public void registerWebSocketHandlers(WebSocketHandlerRegistry 
     registry)  
  { 
    registry.addHandler(createHandler(), 
      "/webSocketHandler").addInterceptors 
      (new HttpSessionHandshakeInterceptor()); 
  } 
  @Bean 
  public WebSocketHandler createMyHandler() { 
    return new MyWebSocketHandler(); 
  } 
} 

The HandshakeInterceptor interface exposes the beforeHandshake() and afterhandshake() methods to customize the WebSocket handshake. The HttpSessionHandshakeInterceptor method facilitates binding information from the HTTP session to the handshake attributes under the name HTTP_SESSION_ID_ATTR_NAME. These attributes can be used as the WebSocketSession.getAttributes() method.