spring session源码解析

<bean class="org.springframework.session.data.redis.config.annotation.web.http.RedisHttpSessionConfiguration"/>

public abstract class AbstractHttpSessionApplicationInitializer
		implements WebApplicationInitializer {

	/**
	 * The default name for Spring Session's repository filter.
	 */
	public static final String DEFAULT_FILTER_NAME = "springSessionRepositoryFilter";
  	public void onStartup(ServletContext servletContext) throws ServletException {

			......

		insertSessionRepositoryFilter(servletContext);
		afterSessionRepositoryFilter(servletContext);
	}

	/**
	 * Registers the springSessionRepositoryFilter.
	 * @param servletContext the {@link ServletContext}
	 */
	private void insertSessionRepositoryFilter(ServletContext servletContext) {
		String filterName = DEFAULT_FILTER_NAME;
		DelegatingFilterProxy springSessionRepositoryFilter = new DelegatingFilterProxy(
				filterName);
		String contextAttribute = getWebApplicationContextAttribute();
		if (contextAttribute != null) {
			springSessionRepositoryFilter.setContextAttribute(contextAttribute);
		}
		registerFilter(servletContext, true, filterName, springSessionRepositoryFilter);
	}
}

/**
* 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;
	this.flushImmediateIfNecessary();
}

public MapSession() {
	this(UUID.randomUUID().toString());
}

@Override
public HttpSessionWrapper getSession(boolean create) {
	HttpSessionWrapper currentSession = getCurrentSession();
	if (currentSession != null) {
		return currentSession;
	}
	// 从request请求中得到sessionId
	String requestedSessionId = getRequestedSessionId();
	if (requestedSessionId != null
			&& getAttribute(INVALID_SESSION_ID_ATTR) == null) {
		S session = getSession(requestedSessionId);
		if (session != null) {
			this.requestedSessionIdValid = true;
			currentSession = new HttpSessionWrapper(session, getServletContext());
			currentSession.setNew(false);
			setCurrentSession(currentSession);
			return currentSession;
		}
		else {
			// This is an invalid session id. No need to ask again if
			// request.getSession is invoked for the duration of this request
			setAttribute(INVALID_SESSION_ID_ATTR, "true");
		}
	}
	if (!create) {
		return null;
	}

	S session = SessionRepositoryFilter.this.sessionRepository.createSession();
	session.setLastAccessedTime(System.currentTimeMillis());
	currentSession = new HttpSessionWrapper(session, getServletContext());
	setCurrentSession(currentSession);
	return currentSession;
}

@Scheduled(cron = "${spring.session.cleanup.cron.expression:0 * * * * *}")
public void cleanupExpiredSessions() {
	this.expirationPolicy.cleanExpiredSessions();
}

public void cleanExpiredSessions() {
	long now = System.currentTimeMillis();
	long prevMin = roundDownMinute(now);

	// preMin时间到，将spring:session:expirations:[min], set集合中members包括了这一分钟之内需要过期的所有
	// expire key删掉, member元素为expires:[sessionId]
	String expirationKey = getExpirationKey(prevMin);
	Set<Object> sessionsToExpire = this.redis.boundSetOps(expirationKey).members();
	this.redis.delete(expirationKey);
	for (Object session : sessionsToExpire) {
		// sessionKey为spring:session:sessions:expires:[sessionId]
		String sessionKey = getSessionKey((String) session);
		//利用redis的惰性删除策略
		touch(sessionKey);
	}
}

public void onExpirationUpdated(Long originalExpirationTimeInMilli,
			ExpiringSession session) {
	String keyToExpire = "expires:" + session.getId();
	long toExpire = roundUpToNextMinute(expiresInMillis(session));

	if (originalExpirationTimeInMilli != null) {
		long originalRoundedUp = roundUpToNextMinute(originalExpirationTimeInMilli);
		// 更新expirations:[min],两个分钟数之内都有这个session，将前一个set中的成员删除
		if (toExpire != originalRoundedUp) {
			String expireKey = getExpirationKey(originalRoundedUp);
			this.redis.boundSetOps(expireKey).remove(keyToExpire);
		}
	}

	long sessionExpireInSeconds = session.getMaxInactiveIntervalInSeconds();
	String sessionKey = getSessionKey(keyToExpire);

	if (sessionExpireInSeconds < 0) {
		this.redis.boundValueOps(sessionKey).append("");
		this.redis.boundValueOps(sessionKey).persist();
		this.redis.boundHashOps(getSessionKey(session.getId())).persist();
		return;
	}

	String expireKey = getExpirationKey(toExpire);
	BoundSetOperations<Object, Object> expireOperations = this.redis
			.boundSetOps(expireKey);
	expireOperations.add(keyToExpire);

	long fiveMinutesAfterExpires = sessionExpireInSeconds
			+ TimeUnit.MINUTES.toSeconds(5);

	// expirations:[min] key的过期时间加5分钟
	expireOperations.expire(fiveMinutesAfterExpires, TimeUnit.SECONDS);
	if (sessionExpireInSeconds == 0) {
		this.redis.delete(sessionKey);
	}
	else {
		// expires:[sessionId] 值为“”，过期时间为MaxInactiveIntervalInSeconds
		this.redis.boundValueOps(sessionKey).append("");
		this.redis.boundValueOps(sessionKey).expire(sessionExpireInSeconds,
				TimeUnit.SECONDS);
	}
	// sessions:[sessionId]的过期时间 加5分钟
	this.redis.boundHashOps(getSessionKey(session.getId()))
			.expire(fiveMinutesAfterExpires, TimeUnit.SECONDS);
}