RedisOperationsSessionRepository

1. uml 圖
   

   MessageListener是redis訊息訂閱的監聽介面，SessionMessageListener 是過時的，已經被
   RedisOperationsSessionRepository所代替，可以從原始碼中看到

2. 原始碼分析

   public class RedisOperationsSessionRepository implements
           FindByIndexNameSessionRepository<RedisOperationsSessionRepository.RedisSession
    
   >,
           MessageListener {
       private static final Log logger = LogFactory
               .getLog(RedisOperationsSessionRepository.class);
   
       private static final String SPRING_SECURITY_CONTEXT = "SPRING_SECURITY_CONTEXT";
   
       static PrincipalNameResolver PRINCIPAL_NAME_RESOLVER = new PrincipalNameResolver();
   
       /**
        * The default prefix for each key and channel in Redis used by Spring Session.
        * 預設key和channel的字首
        */
    
   
       static final String DEFAULT_SPRING_SESSION_REDIS_PREFIX = "spring:session:";
   
       /**
        * The key in the Hash representing
        * {@link org.springframework.session.ExpiringSession#getCreationTime()}.
        */
       static final String CREATION_TIME_ATTR = "creationTime";
   
       /**
        * The key in the Hash representing
        * {@link org.springframework.session.ExpiringSession#getMaxInactiveIntervalInSeconds()}
        * .
        */
    
   
       static final String MAX_INACTIVE_ATTR = "maxInactiveInterval";
   
       /**
        * The key in the Hash representing
        * {@link org.springframework.session.ExpiringSession#getLastAccessedTime()}.
        */
       static final String LAST_ACCESSED_ATTR = "lastAccessedTime";
   
       /**
        * The prefix of the key for used for session attributes. The suffix is the name of
        * the session attribute. For example, if the session contained an attribute named
        * attributeName, then there would be an entry in the hash named
        * sessionAttr:attributeName that mapped to its value.
        * session屬性sessionAttr:attributeName
        */
       static final String SESSION_ATTR_PREFIX = "sessionAttr:";
   
       /**
        * The prefix for every key used by Spring Session in Redis.
        */
       private String keyPrefix = DEFAULT_SPRING_SESSION_REDIS_PREFIX;
       //從uml圖中可以看出這是redis模板操作的介面
       private final RedisOperations<Object, Object> sessionRedisOperations;
       /**
       redis session過期策略處理類。RedisSessionExpirationPolicy與RedisOperationsSessionRepository相互引用，    RedisOperationsSessionRepository去通知RedisSessionExpirationPolicy做相關的操作，同時RedisSessionExpirationPolicy從RedisOperationsSessionRepository拉取相關的資訊。特別像觀察者模式中的“拉操作”，可以認為是簡版的觀察者模式
       **/
       private final RedisSessionExpirationPolicy expirationPolicy;
       /**
       * 事件釋出
       **/
       private ApplicationEventPublisher eventPublisher = new ApplicationEventPublisher() {
           public void publishEvent(ApplicationEvent event) {
           }
   
           public void publishEvent(Object event) {
           }
       };
   
       /**
        * If non-null, this value is used to override the default value for
        * {@link RedisSession#setMaxInactiveIntervalInSeconds(int)}.
        */
       private Integer defaultMaxInactiveInterval;
       //預設redis序列化使用的jdk序列化方式
       private RedisSerializer<Object> defaultSerializer = new JdkSerializationRedisSerializer();
   
       private RedisFlushMode redisFlushMode = RedisFlushMode.ON_SAVE;
   
       /**
        * Allows creating an instance and uses a default {@link RedisOperations} for both
        * managing the session and the expirations.
        *
        * @param redisConnectionFactory the {@link RedisConnectionFactory} to use.
        */
       public RedisOperationsSessionRepository(
               RedisConnectionFactory redisConnectionFactory) {
           this(createDefaultTemplate(redisConnectionFactory));
       }
   
       /**
        * Creates a new instance. For an example, refer to the class level javadoc.
        *
        * @param sessionRedisOperations The {@link RedisOperations} to use for managing the
        * sessions. Cannot be null.
        */
       public RedisOperationsSessionRepository(
               RedisOperations<Object, Object> sessionRedisOperations) {
           Assert.notNull(sessionRedisOperations, "sessionRedisOperations cannot be null");
           this.sessionRedisOperations = sessionRedisOperations;
           this.expirationPolicy = new RedisSessionExpirationPolicy(sessionRedisOperations,
                   this);
       }
   
       /**
        * Sets the {@link ApplicationEventPublisher} that is used to publish
        * {@link SessionDestroyedEvent}. The default is to not publish a
        * {@link SessionDestroyedEvent}.
        *
        * @param applicationEventPublisher the {@link ApplicationEventPublisher} that is used
        * to publish {@link SessionDestroyedEvent}. Cannot be null.
        */
       public void setApplicationEventPublisher(
               ApplicationEventPublisher applicationEventPublisher) {
           Assert.notNull(applicationEventPublisher,
                   "applicationEventPublisher cannot be null");
           this.eventPublisher = applicationEventPublisher;
       }
   
       /**
        * Sets the maximum inactive interval in seconds between requests before newly created
        * sessions will be invalidated. A negative time indicates that the session will never
        * timeout. The default is 1800 (30 minutes).
        *
        * @param defaultMaxInactiveInterval the number of seconds that the {@link Session}
        * should be kept alive between client requests.
        */
       public void setDefaultMaxInactiveInterval(int defaultMaxInactiveInterval) {
           this.defaultMaxInactiveInterval = defaultMaxInactiveInterval;
       }
   
       /**
        * Sets the default redis serializer. Replaces default serializer which is based on
        * {@link JdkSerializationRedisSerializer}.
        *
        * @param defaultSerializer the new default redis serializer
        */
       public void setDefaultSerializer(RedisSerializer<Object> defaultSerializer) {
           Assert.notNull(defaultSerializer, "defaultSerializer cannot be null");
           this.defaultSerializer = defaultSerializer;
       }
   
       /**
        * Sets the redis flush mode. Default flush mode is {@link RedisFlushMode#ON_SAVE}.
        *
        * @param redisFlushMode the new redis flush mode
        */
       public void setRedisFlushMode(RedisFlushMode redisFlushMode) {
           Assert.notNull(redisFlushMode, "redisFlushMode cannot be null");
           this.redisFlushMode = redisFlushMode;
       }
   
       public void save(RedisSession session) {
           session.saveDelta();
           if (session.isNew()) {
               String sessionCreatedKey = getSessionCreatedChannel(session.getId());
               this.sessionRedisOperations.convertAndSend(sessionCreatedKey, session.delta);
               session.setNew(false);
           }
       }
   
       /*
       清理session
       */
       @Scheduled(cron = "0 * * * * *")
       public void cleanupExpiredSessions() {
           this.expirationPolicy.cleanExpiredSessions();
       }
   
       public RedisSession getSession(String id) {
           return getSession(id, false);
       }
   
       public Map<String, RedisSession> findByIndexNameAndIndexValue(String indexName,
               String indexValue) {
           if (!PRINCIPAL_NAME_INDEX_NAME.equals(indexName)) {
               return Collections.emptyMap();
           }
           String principalKey = getPrincipalKey(indexValue);
           Set<Object> sessionIds = this.sessionRedisOperations.boundSetOps(principalKey)
                   .members();
           Map<String, RedisSession> sessions = new HashMap<String, RedisSession>(
                   sessionIds.size());
           for (Object id : sessionIds) {
               RedisSession session = getSession((String) id);
               if (session != null) {
                   sessions.put(session.getId(), session);
               }
           }
           return sessions;
       }
   
       /**
        * Gets the session.
        * @param id the session id
        * @param allowExpired if true, will also include expired sessions that have not been
        * deleted. If false, will ensure expired sessions are not returned.
        * @return the Redis session
        */
       private RedisSession getSession(String id, boolean allowExpired) {
           Map<Object, Object> entries = getSessionBoundHashOperations(id).entries();
           if (entries.isEmpty()) {
               return null;
           }
           MapSession loaded = loadSession(id, entries);
           if (!allowExpired && loaded.isExpired()) {
               return null;
           }
           RedisSession result = new RedisSession(loaded);
           result.originalLastAccessTime = loaded.getLastAccessedTime();
           return result;
       }
   
       private MapSession loadSession(String id, Map<Object, Object> entries) {
           MapSession loaded = new MapSession(id);
           for (Map.Entry<Object, Object> entry : entries.entrySet()) {
               String key = (String) entry.getKey();
               if (CREATION_TIME_ATTR.equals(key)) {
                   loaded.setCreationTime((Long) entry.getValue());
               }
               else if (MAX_INACTIVE_ATTR.equals(key)) {
                   loaded.setMaxInactiveIntervalInSeconds((Integer) entry.getValue());
               }
               else if (LAST_ACCESSED_ATTR.equals(key)) {
                   loaded.setLastAccessedTime((Long) entry.getValue());
               }
               else if (key.startsWith(SESSION_ATTR_PREFIX)) {
                   loaded.setAttribute(key.substring(SESSION_ATTR_PREFIX.length()),
                           entry.getValue());
               }
           }
           return loaded;
       }
   
       public void delete(String sessionId) {
           RedisSession session = getSession(sessionId, true);
           if (session == null) {
               return;
           }
   
           cleanupPrincipalIndex(session);
           this.expirationPolicy.onDelete(session);
   
           String expireKey = getExpiredKey(session.getId());
           this.sessionRedisOperations.delete(expireKey);
   
           session.setMaxInactiveIntervalInSeconds(0);
           save(session);
       }
   
       public RedisSession createSession() {
           RedisSession redisSession = new RedisSession();
           if (this.defaultMaxInactiveInterval != null) {
               redisSession.setMaxInactiveIntervalInSeconds(this.defaultMaxInactiveInterval);
           }
           return redisSession;
       }
   
       @SuppressWarnings("unchecked")
       public void onMessage(Message message, byte[] pattern) {
           byte[] messageChannel = message.getChannel();
           byte[] messageBody = message.getBody();
           if (messageChannel == null || messageBody == null) {
               return;
           }
   
           String channel = new String(messageChannel);
   
           if (channel.startsWith(getSessionCreatedChannelPrefix())) {
               // TODO: is this thread safe?
               Map<Object, Object> loaded = (Map<Object, Object>) this.defaultSerializer
                       .deserialize(message.getBody());
               handleCreated(loaded, channel);
               return;
           }
   
           String body = new String(messageBody);
           if (!body.startsWith(getExpiredKeyPrefix())) {
               return;
           }
   
           boolean isDeleted = channel.endsWith(":del");
           if (isDeleted || channel.endsWith(":expired")) {
               int beginIndex = body.lastIndexOf(":") + 1;
               int endIndex = body.length();
               String sessionId = body.substring(beginIndex, endIndex);
   
               RedisSession session = getSession(sessionId, true);
   
               if (logger.isDebugEnabled()) {
                   logger.debug("Publishing SessionDestroyedEvent for session " + sessionId);
               }
   
               cleanupPrincipalIndex(session);
   
               if (isDeleted) {
                   handleDeleted(sessionId, session);
               }
               else {
                   handleExpired(sessionId, session);
               }
   
               return;
           }
       }
   
       private void cleanupPrincipalIndex(RedisSession session) {
           if (session == null) {
               return;
           }
           String sessionId = session.getId();
           String principal = PRINCIPAL_NAME_RESOLVER.resolvePrincipal(session);
           if (principal != null) {
               this.sessionRedisOperations.boundSetOps(getPrincipalKey(principal))
                       .remove(sessionId);
           }
       }
   
       public void handleCreated(Map<Object, Object> loaded, String channel) {
           String id = channel.substring(channel.lastIndexOf(":") + 1);
           ExpiringSession session = loadSession(id, loaded);
           publishEvent(new SessionCreatedEvent(this, session));
       }
   
       private void handleDeleted(String sessionId, RedisSession session) {
           if (session == null) {
               publishEvent(new SessionDeletedEvent(this, sessionId));
           }
           else {
               publishEvent(new SessionDeletedEvent(this, session));
           }
       }
   
       private void handleExpired(String sessionId, RedisSession session) {
           if (session == null) {
               publishEvent(new SessionExpiredEvent(this, sessionId));
           }
           else {
               publishEvent(new SessionExpiredEvent(this, session));
           }
       }
   
       private void publishEvent(ApplicationEvent event) {
           try {
               this.eventPublisher.publishEvent(event);
           }
           catch (Throwable ex) {
               logger.error("Error publishing " + event + ".", ex);
           }
       }
   
       public void setRedisKeyNamespace(String namespace) {
           this.keyPrefix = DEFAULT_SPRING_SESSION_REDIS_PREFIX + namespace + ":";
       }
   
       /**
        * Gets the Hash key for this session by prefixing it appropriately.
        *
        * @param sessionId the session id
        * @return the Hash key for this session by prefixing it appropriately.
        */
       String getSessionKey(String sessionId) {
           return this.keyPrefix + "sessions:" + sessionId;
       }
   
       String getPrincipalKey(String principalName) {
           return this.keyPrefix + "index:"
                   + FindByIndexNameSessionRepository.PRINCIPAL_NAME_INDEX_NAME + ":"
                   + principalName;
       }
   
       String getExpirationsKey(long expiration) {
           return this.keyPrefix + "expirations:" + expiration;
       }
   
       private String getExpiredKey(String sessionId) {
           return getExpiredKeyPrefix() + sessionId;
       }
   
       private String getSessionCreatedChannel(String sessionId) {
           return getSessionCreatedChannelPrefix() + sessionId;
       }
   
       /**
       *過期key的字首
       **/
       private String getExpiredKeyPrefix() {
           return this.keyPrefix + "sessions:" + "expires:";
       }
   
       /**
        * Gets the prefix for the channel that SessionCreatedEvent are published to. The
        * suffix is the session id of the session that was created.
        *
        * @return the prefix for the channel that SessionCreatedEvent are published to
        */
       public String getSessionCreatedChannelPrefix() {
           return this.keyPrefix + "event:created:";
       }
   
       /**
        * Gets the {@link BoundHashOperations} to operate on a {@link Session}.
        * @param sessionId the id of the {@link Session} to work with
        * @return the {@link BoundHashOperations} to operate on a {@link Session}
        */
       private BoundHashOperations<Object, Object, Object> getSessionBoundHashOperations(
               String sessionId) {
           String key = getSessionKey(sessionId);
           return this.sessionRedisOperations.boundHashOps(key);
       }
   
       /**
        * Gets the key for the specified session attribute.
        *
        * @param attributeName the attribute name
        * @return the attribute key name
        */
       static String getSessionAttrNameKey(String attributeName) {
           return SESSION_ATTR_PREFIX + attributeName;
       }
   
       private static RedisTemplate<Object, Object> createDefaultTemplate(
               RedisConnectionFactory connectionFactory) {
           Assert.notNull(connectionFactory, "connectionFactory cannot be null");
           RedisTemplate<Object, Object> template = new RedisTemplate<Object, Object>();
           template.setKeySerializer(new StringRedisSerializer());
           template.setHashKeySerializer(new StringRedisSerializer());
           template.setConnectionFactory(connectionFactory);
           template.afterPropertiesSet();
           return template;
       }
   
       /**
        * A custom implementation of {@link Session} that uses a {@link MapSession} as the
        * basis for its mapping. It keeps track of any attributes that have changed. When
        * {@link org.springframework.session.data.redis.RedisOperationsSessionRepository.RedisSession#saveDelta()}
        * is invoked all the attributes that have been changed will be persisted.
        *
        * @author Rob Winch
        * @since 1.0
        */
       final class RedisSession implements ExpiringSession {
           private final MapSession cached;
           private Long originalLastAccessTime;
           private Map<String, Object> delta = new HashMap<String, Object>();
           private boolean isNew;
           private String originalPrincipalName;
   
           /**
            * Creates a new instance ensuring to mark all of the new attributes to be
            * persisted in the next save operation.
            */
           RedisSession() {
               this(new MapSession());
               this.delta.put(CREATION_TIME_ATTR, getCreationTime());
               this.delta.put(MAX_INACTIVE_ATTR, getMaxInactiveIntervalInSeconds());
               this.delta.put(LAST_ACCESSED_ATTR, getLastAccessedTime());
               this.isNew = true;
               flushImmediateIfNecessary();
           }
   
           /**
            * Creates a new instance from the provided {@link MapSession}.
            *
            * @param cached the {@MapSession} that represents the persisted session that was
            * retrieved. Cannot be null.
            */
           RedisSession(MapSession cached) {
               Assert.notNull("MapSession cannot be null");
               this.cached = cached;
               this.originalPrincipalName = PRINCIPAL_NAME_RESOLVER.resolvePrincipal(this);
           }
   
           public void setNew(boolean isNew) {
               this.isNew = isNew;
           }
   
           public void setLastAccessedTime(long lastAccessedTime) {
               this.cached.setLastAccessedTime(lastAccessedTime);
               this.delta.put(LAST_ACCESSED_ATTR, getLastAccessedTime());
               flushImmediateIfNecessary();
           }
   
           public boolean isExpired() {
               return this.cached.isExpired();
           }
   
           public boolean isNew() {
               return this.isNew;
           }
   
           public long getCreationTime() {
               return this.cached.getCreationTime();
           }
   
           public String getId() {
               return this.cached.getId();
           }
   
           public long getLastAccessedTime() {
               return this.cached.getLastAccessedTime();
           }
   
           public void setMaxInactiveIntervalInSeconds(int interval) {
               this.cached.setMaxInactiveIntervalInSeconds(interval);
               this.delta.put(MAX_INACTIVE_ATTR, getMaxInactiveIntervalInSeconds());
               flushImmediateIfNecessary();
           }
   
           public int getMaxInactiveIntervalInSeconds() {
               return this.cached.getMaxInactiveIntervalInSeconds();
           }
   
           @SuppressWarnings("unchecked")
           public Object getAttribute(String attributeName) {
               return this.cached.getAttribute(attributeName);
           }
   
           public Set<String> getAttributeNames() {
               return this.cached.getAttributeNames();
           }
   
           public void setAttribute(String attributeName, Object attributeValue) {
               this.cached.setAttribute(attributeName, attributeValue);
               this.delta.put(getSessionAttrNameKey(attributeName), attributeValue);
               flushImmediateIfNecessary();
           }
   
           public void removeAttribute(String attributeName) {
               this.cached.removeAttribute(attributeName);
               this.delta.put(getSessionAttrNameKey(attributeName), null);
               flushImmediateIfNecessary();
           }
   
           private void flushImmediateIfNecessary() {
               if (RedisOperationsSessionRepository.this.redisFlushMode == RedisFlushMode.IMMEDIATE) {
                   saveDelta();
               }
           }
   
           /**
            * Saves any attributes that have been changed and updates the expiration of this
            * session.
            */
           private void saveDelta() {
               if (this.delta.isEmpty()) {
                   return;
               }
               String sessionId = getId();
               getSessionBoundHashOperations(sessionId).putAll(this.delta);
               String principalSessionKey = getSessionAttrNameKey(
                       FindByIndexNameSessionRepository.PRINCIPAL_NAME_INDEX_NAME);
               String securityPrincipalSessionKey = getSessionAttrNameKey(
                       SPRING_SECURITY_CONTEXT);
               if (this.delta.containsKey(principalSessionKey)
                       || this.delta.containsKey(securityPrincipalSessionKey)) {
                   if (this.originalPrincipalName != null) {
                       String originalPrincipalRedisKey = getPrincipalKey(
                               this.originalPrincipalName);
                       RedisOperationsSessionRepository.this.sessionRedisOperations
                               .boundSetOps(originalPrincipalRedisKey).remove(sessionId);
                   }
                   String principal = PRINCIPAL_NAME_RESOLVER.resolvePrincipal(this);
                   this.originalPrincipalName = principal;
                   if (principal != null) {
                       String principalRedisKey = getPrincipalKey(principal);
                       RedisOperationsSessionRepository.this.sessionRedisOperations
                               .boundSetOps(principalRedisKey).add(sessionId);
                   }
               }
   
               this.delta = new HashMap<String, Object>(this.delta.size());
   
               Long originalExpiration = this.originalLastAccessTime == null ? null
                       : this.originalLastAccessTime + TimeUnit.SECONDS
                               .toMillis(getMaxInactiveIntervalInSeconds());
               RedisOperationsSessionRepository.this.expirationPolicy
                       .onExpirationUpdated(originalExpiration, this);
           }
       }
   
       /**
        * Principal name resolver helper class.
        */
       static class PrincipalNameResolver {
           private SpelExpressionParser parser = new SpelExpressionParser();
   
           public String resolvePrincipal(Session session) {
               String principalName = session.getAttribute(PRINCIPAL_NAME_INDEX_NAME);
               if (principalName != null) {
                   return principalName;
               }
               Object authentication = session.getAttribute(SPRING_SECURITY_CONTEXT);
               if (authentication != null) {
                   Expression expression = this.parser
                           .parseExpression("authentication?.name");
                   return expression.getValue(authentication, String.class);
               }
               return null;
           }
   
       }
   }

3. 儲存結構