org.springframework.web.reactive.socket

Interface WebSocketHandler

public interface WebSocketHandler

Handler for a WebSocket session.

A server WebSocketHandler is mapped to requests with SimpleUrlHandlerMapping and WebSocketHandlerAdapter. A client WebSocketHandler is passed to the WebSocketClient execute method.

Use session.receive() to compose on the inbound message stream, and session.send(publisher) for the outbound message stream. Below is an example, combined flow to process inbound and to send outbound messages:

 class ExampleHandler implements WebSocketHandler {

        @Override
        public Mono<Void> handle(WebSocketSession session) {

                Flux<WebSocketMessage> input = session.receive()
                        .doOnNext(message -> {
                                // ...
                        })
                        .concatMap(message -> {
                                // ...
                        })
                        .map(value -> session.textMessage("Echo " + value));

                return session.send(output);
        }
 }
 

If processing inbound and sending outbound messages are independent streams, they can be joined together with the "zip" operator:

 class ExampleHandler implements WebSocketHandler {

        @Override
        public Mono<Void> handle(WebSocketSession session) {

                Mono<Void> input = session.receive()
                        .doOnNext(message -> {
                                // ...
                        })
                        .concatMap(message -> {
                                // ...
                        })
                        .then();

                Flux<String> source = ... ;
                Mono<Void> output = session.send(source.map(session::textMessage));

                return Mono.zip(input, output).then();
        }
 }
 

A WebSocketHandler must compose the inbound and outbound streams into a unified flow and return a Mono<Void> that reflects the completion of that flow. That means there is no need to check if the connection is open, since Reactive Streams signals will terminate activity. The inbound stream receives a completion/error signal, and the outbound stream receives receives a cancellation signal.

Since:

5.0

Author:

Rossen Stoyanchev

Method Summary

Modifier and Type	Method and Description
default java.util.List<java.lang.String>	getSubProtocols() Return the list of sub-protocols supported by this handler.
reactor.core.publisher.Mono<java.lang.Void>	handle(WebSocketSession session) Invoked when a new WebSocket connection is established, and allows handling of the session.

Method Detail

getSubProtocols

default java.util.List<java.lang.String> getSubProtocols()

Return the list of sub-protocols supported by this handler.

By default an empty list is returned.

handle

reactor.core.publisher.Mono<java.lang.Void> handle(WebSocketSession session)

Invoked when a new WebSocket connection is established, and allows handling of the session.

See the class-level doc and the reference for more details and examples of how to handle the session.

Parameters:

session - the session to handle

Returns:

indicates when appilcation handling of the session is complete, which should reflect the completion of the inbound message stream (i.e. connection closing) and possibly the completion of the outbound message stream and the writing of messages.