Logback is intended as a successor to the popular log4j project,picking up where log4j leaves off.

请参阅Sifting Appender的文档

The SiftingAppender is unique in its capacity to reference and configure nested appenders. In the above example,within the SiftingAppender there will be nested FileAppender instances,each instance identified by the value associated with the “userid” MDC key. Whenever the “userid” MDC key is assigned a new value,a new FileAppender instance will be built from scratch. The SiftingAppender keeps track of the appenders it creates. Appenders unused for 30 minutes will be automatically closed and discarded.

在该示例中,它们基于MDC值为每个用户生成单独的日志文件.可以根据您的需要使用其他MDC值.