[logback-user] Logback Spring Extension

I follow the configuration described at: https://github.com/qos-ch/logback-extensions/wiki/Spring but the one piece i don't understand is: <bean class="ch.qos.logback.classic.encoder.PatternLayoutEncoder" init-method="start" destroy-method="stop"> <property name="context" value="#{ T(org.slf4j.LoggerFactory).getILoggerFactory() }"/> <property name="pattern" value="%date %-5level [%thread] %logger{36} %m%n"/> </bean> The result of org.slf4j.LoggerFactory.getILoggerFactory() is a an ILoggerFactory which shares no class hierarchy with a ch.qos.logback.core.Context. What is happening here?