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.messaging.simp;
018
019import java.util.Map;
020
021import org.apache.commons.logging.Log;
022
023import org.springframework.lang.Nullable;
024import org.springframework.messaging.Message;
025import org.springframework.messaging.MessageHeaders;
026import org.springframework.util.Assert;
027import org.springframework.util.StringUtils;
028
029/**
030 * A wrapper class for access to attributes associated with a SiMP session
031 * (e.g. WebSocket session).
032 *
033 * @author Rossen Stoyanchev
034 * @since 4.1
035 */
036public class SimpAttributes {
037
038        /** Key for the mutex session attribute. */
039        public static final String SESSION_MUTEX_NAME = SimpAttributes.class.getName() + ".MUTEX";
040
041        /** Key set after the session is completed. */
042        public static final String SESSION_COMPLETED_NAME = SimpAttributes.class.getName() + ".COMPLETED";
043
044        /** Prefix for the name of session attributes used to store destruction callbacks. */
045        public static final String DESTRUCTION_CALLBACK_NAME_PREFIX =
046                        SimpAttributes.class.getName() + ".DESTRUCTION_CALLBACK.";
047
048        private static final Log logger = SimpLogging.forLogName(SimpAttributes.class);
049
050
051        private final String sessionId;
052
053        private final Map<String, Object> attributes;
054
055
056        /**
057         * Constructor wrapping the given session attributes map.
058         * @param sessionId the id of the associated session
059         * @param attributes the attributes
060         */
061        public SimpAttributes(String sessionId, Map<String, Object> attributes) {
062                Assert.notNull(sessionId, "'sessionId' is required");
063                Assert.notNull(attributes, "'attributes' is required");
064                this.sessionId = sessionId;
065                this.attributes = attributes;
066        }
067
068
069        /**
070         * Return the value for the attribute of the given name, if any.
071         * @param name the name of the attribute
072         * @return the current attribute value, or {@code null} if not found
073         */
074        @Nullable
075        public Object getAttribute(String name) {
076                return this.attributes.get(name);
077        }
078
079        /**
080         * Set the value with the given name replacing an existing value (if any).
081         * @param name the name of the attribute
082         * @param value the value for the attribute
083         */
084        public void setAttribute(String name, Object value) {
085                this.attributes.put(name, value);
086        }
087
088        /**
089         * Remove the attribute of the given name, if it exists.
090         * <p>Also removes the registered destruction callback for the specified
091         * attribute, if any. However it <i>does not</i> execute the callback.
092         * It is assumed the removed object will continue to be used and destroyed
093         * independently at the appropriate time.
094         * @param name the name of the attribute
095         */
096        public void removeAttribute(String name) {
097                this.attributes.remove(name);
098                removeDestructionCallback(name);
099        }
100
101        /**
102         * Retrieve the names of all attributes.
103         * @return the attribute names as String array, never {@code null}
104         */
105        public String[] getAttributeNames() {
106                return StringUtils.toStringArray(this.attributes.keySet());
107        }
108
109        /**
110         * Register a callback to execute on destruction of the specified attribute.
111         * The callback is executed when the session is closed.
112         * @param name the name of the attribute to register the callback for
113         * @param callback the destruction callback to be executed
114         */
115        public void registerDestructionCallback(String name, Runnable callback) {
116                synchronized (getSessionMutex()) {
117                        if (isSessionCompleted()) {
118                                throw new IllegalStateException("Session id=" + getSessionId() + " already completed");
119                        }
120                        this.attributes.put(DESTRUCTION_CALLBACK_NAME_PREFIX + name, callback);
121                }
122        }
123
124        private void removeDestructionCallback(String name) {
125                synchronized (getSessionMutex()) {
126                        this.attributes.remove(DESTRUCTION_CALLBACK_NAME_PREFIX + name);
127                }
128        }
129
130        /**
131         * Return an id for the associated session.
132         * @return the session id as String (never {@code null})
133         */
134        public String getSessionId() {
135                return this.sessionId;
136        }
137
138        /**
139         * Expose the object to synchronize on for the underlying session.
140         * @return the session mutex to use (never {@code null})
141         */
142        public Object getSessionMutex() {
143                Object mutex = this.attributes.get(SESSION_MUTEX_NAME);
144                if (mutex == null) {
145                        mutex = this.attributes;
146                }
147                return mutex;
148        }
149
150        /**
151         * Whether the {@link #sessionCompleted()} was already invoked.
152         */
153        public boolean isSessionCompleted() {
154                return (this.attributes.get(SESSION_COMPLETED_NAME) != null);
155        }
156
157        /**
158         * Invoked when the session is completed. Executed completion callbacks.
159         */
160        public void sessionCompleted() {
161                synchronized (getSessionMutex()) {
162                        if (!isSessionCompleted()) {
163                                executeDestructionCallbacks();
164                                this.attributes.put(SESSION_COMPLETED_NAME, Boolean.TRUE);
165                        }
166                }
167        }
168
169        private void executeDestructionCallbacks() {
170                this.attributes.forEach((key, value) -> {
171                        if (key.startsWith(DESTRUCTION_CALLBACK_NAME_PREFIX)) {
172                                try {
173                                        ((Runnable) value).run();
174                                }
175                                catch (Throwable ex) {
176                                        logger.error("Uncaught error in session attribute destruction callback", ex);
177                                }
178                        }
179                });
180        }
181
182
183        /**
184         * Extract the SiMP session attributes from the given message and
185         * wrap them in a {@link SimpAttributes} instance.
186         * @param message the message to extract session attributes from
187         */
188        public static SimpAttributes fromMessage(Message<?> message) {
189                Assert.notNull(message, "Message must not be null");
190                MessageHeaders headers = message.getHeaders();
191                String sessionId = SimpMessageHeaderAccessor.getSessionId(headers);
192                Map<String, Object> sessionAttributes = SimpMessageHeaderAccessor.getSessionAttributes(headers);
193                if (sessionId == null) {
194                        throw new IllegalStateException("No session id in " + message);
195                }
196                if (sessionAttributes == null) {
197                        throw new IllegalStateException("No session attributes in " + message);
198                }
199                return new SimpAttributes(sessionId, sessionAttributes);
200        }
201
202}