001/*
002 * Copyright 2002-2018 the original author or authors.
003 *
004 * Licensed under the Apache License, Version 2.0 (the "License");
005 * you may not use this file except in compliance with the License.
006 * You may obtain a copy of the License at
007 *
008 *      https://www.apache.org/licenses/LICENSE-2.0
009 *
010 * Unless required by applicable law or agreed to in writing, software
011 * distributed under the License is distributed on an "AS IS" BASIS,
012 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
013 * See the License for the specific language governing permissions and
014 * limitations under the License.
015 */
016
017package org.springframework.web.socket.messaging;
018
019import java.util.List;
020
021import org.springframework.lang.Nullable;
022import org.springframework.messaging.Message;
023import org.springframework.messaging.MessageChannel;
024import org.springframework.web.socket.CloseStatus;
025import org.springframework.web.socket.WebSocketMessage;
026import org.springframework.web.socket.WebSocketSession;
027
028/**
029 * A contract for handling WebSocket messages as part of a higher level protocol,
030 * referred to as "sub-protocol" in the WebSocket RFC specification.
031 * Handles both {@link WebSocketMessage WebSocketMessages} from a client
032 * as well as {@link Message Messages} to a client.
033 *
034 * <p>Implementations of this interface can be configured on a
035 * {@link SubProtocolWebSocketHandler} which selects a sub-protocol handler to
036 * delegate messages to based on the sub-protocol requested by the client through
037 * the {@code Sec-WebSocket-Protocol} request header.
038 *
039 * @author Andy Wilkinson
040 * @author Rossen Stoyanchev
041 * @since 4.0
042 */
043public interface SubProtocolHandler {
044
045        /**
046         * Return the list of sub-protocols supported by this handler (never {@code null}).
047         */
048        List<String> getSupportedProtocols();
049
050        /**
051         * Handle the given {@link WebSocketMessage} received from a client.
052         * @param session the client session
053         * @param message the client message
054         * @param outputChannel an output channel to send messages to
055         */
056        void handleMessageFromClient(WebSocketSession session, WebSocketMessage<?> message, MessageChannel outputChannel)
057                        throws Exception;
058
059        /**
060         * Handle the given {@link Message} to the client associated with the given WebSocket session.
061         * @param session the client session
062         * @param message the client message
063         */
064        void handleMessageToClient(WebSocketSession session, Message<?> message) throws Exception;
065
066        /**
067         * Resolve the session id from the given message or return {@code null}.
068         * @param message the message to resolve the session id from
069         */
070        @Nullable
071        String resolveSessionId(Message<?> message);
072
073        /**
074         * Invoked after a {@link WebSocketSession} has started.
075         * @param session the client session
076         * @param outputChannel a channel
077         */
078        void afterSessionStarted(WebSocketSession session, MessageChannel outputChannel) throws Exception;
079
080        /**
081         * Invoked after a {@link WebSocketSession} has ended.
082         * @param session the client session
083         * @param closeStatus the reason why the session was closed
084         * @param outputChannel a channel
085         */
086        void afterSessionEnded(WebSocketSession session, CloseStatus closeStatus, MessageChannel outputChannel)
087                        throws Exception;
088
089}