public void clear() throws CacheException {
        if (LOGGER.isTraceEnabled()) {
            LOGGER.trace("Clearing all objects from cache [" + cache.getName() + "]");
        }
        try {
            cache.removeAll();
        } catch (Throwable t) {
            throw new CacheException(t);
        }
    }
Removes all elements in the cache, but leaves the cache in a useable state.
support/ehcache/src/main/java/org/apache/shiro/cache/ehcache/EhCache.java