001/* 002 * Copyright 2002-2016 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.messaging.simp.user; 018 019import org.springframework.lang.Nullable; 020import org.springframework.messaging.Message; 021 022/** 023 * A strategy for resolving a "user" destination by translating it to one or more 024 * actual destinations one per active user session. When sending a message to a 025 * user destination, the destination must contain the user name so it may be 026 * extracted and used to look up the user sessions. When subscribing to a user 027 * destination, the destination does not have to contain the user's own name. 028 * We simply use the current session. 029 * 030 * <p>See implementation classes and the documentation for example destinations. 031 * 032 * @author Rossen Stoyanchev 033 * @since 4.0 034 * 035 * @see org.springframework.messaging.simp.user.DefaultUserDestinationResolver 036 * @see UserDestinationMessageHandler 037 */ 038@FunctionalInterface 039public interface UserDestinationResolver { 040 041 /** 042 * Resolve the given message with a user destination to one or more messages 043 * with actual destinations, one for each active user session. 044 * @param message the message to try to resolve 045 * @return 0 or more target messages (one for each active session), or 046 * {@code null} if the source message does not contain a user destination. 047 */ 048 @Nullable 049 UserDestinationResult resolveDestination(Message<?> message); 050 051}