* @param key
* 分类键
* @return 日志输出器, 后验条件: 不返回null.
*/
public static Logger getLogger(Class<?> key) {
FailsafeLogger logger = LOGGERS.get(key.getName());
if (logger == null) {
LOGGERS.putIfAbsent(key.getName(), new FailsafeLogger(LOGGER_ADAPTER.getLogger(key)));
logger = LOGGERS.get(key.getName());
}
return logger;
}