public void setCacheManager(CacheManager cacheManager) {
        this.cacheManager = cacheManager;
    }
Sets the cacheManager to use for acquiring the {@link #getActiveSessionsCache() activeSessionsCache} if
one is not configured.

@param cacheManager the manager to use for constructing the session cache.
core/src/main/java/org/apache/shiro/session/mgt/eis/CachingSessionDAO.java