Application error ------ Message: cache_dir "" must be a directory ------ Build: 3.1.8 20150226 PHP Version: 5.4.14 User Agent: Mozilla/5.0 (Windows NT 6.1) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/45.0.2454.101 Safari/537.36 ------ exception 'Zend_Cache_Exception' with message 'cache_dir "" must be a directory' in /ace/app/webroot/system/Zend/Cache.php:209 Stack trace: #0 /ace/app/webroot/system/Zend/Cache/Backend/File.php(177): Zend_Cache::throwException('cache_dir "" mu...') #1 /ace/app/webroot/system/Zend/Cache/Backend/File.php(128): Zend_Cache_Backend_File->setCacheDir(false) #2 /ace/app/webroot/system/Zend/Cache.php(153): Zend_Cache_Backend_File->__construct(Array) #3 /ace/app/webroot/system/Zend/Cache.php(94): Zend_Cache::_makeBackend('File', Array, false, false) #4 /ace/app/webroot/system/core/cache.php(74): Zend_Cache::factory('Core', 'File', Array, Array) #5 /ace/app/webroot/system/functions.inc.php(543): core_cache->__construct() #6 /ace/app/webroot/system/aws_app.inc.php(390): load_class('core_cache') #7 /ace/app/webroot/models/account.php(1191): AWS_APP::cache() #8 /ace/app/webroot/models/account.php(1305): account_class->get_user_group_by_id(1) #9 /ace/app/webroot/system/aws_controller.inc.php(36): account_class->get_user_group(1, 5) #10 /ace/app/webroot/system/aws_app.inc.php(215): AWS_CONTROLLER->__construct() #11 /ace/app/webroot/system/aws_app.inc.php(60): AWS_APP::create_controller('main', '/ace/app/webroo...') #12 /ace/app/webroot/index.php(23): AWS_APP::run() #13 {main}   缓存的问题？怎么解决？