从日志框架转到SLF4J

jul-to-slf4j：jdk-logging到slf4j的桥梁
log4j-over-slf4j：log4j1到slf4j的桥梁
jcl-over-slf4j：commons-logging到slf4j的桥梁

从SLF4J转向具体的日志框架

slf4j-jdk14：slf4j到jdk-logging的桥梁
slf4j-log4j12：slf4j到log4j1的桥梁
log4j-slf4j-impl：slf4j到log4j2的桥梁
logback-classic：slf4j到logback的桥梁
slf4j-jcl：slf4j到commons-logging的桥梁

SLF4J 充当中介

Log4J  转 LogBack  实例 

加入 log4j-over-slf4j.jar 将 Log4J 转成 SLF4J
再加入 logback-classic.jar 将 SLF4J 转成 LogBack


log4j-over-slf4j.jar    log4j >> SLF4J
logback-classic.jar     slf4j >> LogBack