slf4j是一系列的日志接口，而log4j、logback是具体实现了的日志框架。
log4j：是apache实现的一个开源日志组件。
logback：同样是由log4j的作者设计完成的，拥有更好的特性，用来取代log4j的一个日志框架。是slf4j的原生实现，也就是说logback实现slf4j是不消耗内存和计算开销的。
Logback是SpringBoot内置的日志处理框架,spring-boot-starter其中包含了spring-boot-starter-logging，该依赖内容就是 Spring Boot 默认的日志框架 logback。
Logback相比log4j的优势，
比log4j更快，重写了内核，在一些关键路径上性能提升10倍，内存占用也更少。
经过大量的测试，和log4j测试不在一个量级。
logback-classic是SLF4J的实现，切换其他日志框架非常方便，
文档丰富并且不断更新，支持Groovy风格的配置文件
配置文件自动重新加载，如果更新了配置文件，logback-classic可以自动重新加载。
自动压缩归档的日志文件，压缩文件是异步进行，不影响应用。
配置文件可以处理不同的环境开发，测试，生产，这样一个配置文件就可以适应多个环境。
官方文档：http://logback.qos.ch/manual/
logback有5种日志级别，等级从低到高分别是TRACE < DEBUG < INFO < WARN < ERROR
Trace:是追踪，就是程序推进以下
Debug:指出细粒度信息事件对调试应用程序是非常有帮助的.
Info:消息在粗粒度级别上突出强调应用程序的运行过程.
Warn:输出警告及warn以下级别的日志.
Error:输出错误信息日志.
OFF表示关闭全部日志
ALL表示开启全部日志。
@Slf4j
Log.debug() / log.info()/ log.warn() / log.error()
<?xml version="1.0" encoding="UTF-8"?>
<configuration
????????xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
????????xsi:noNamespaceSchemaLocation="http://www.padual.com/java/logback.xsd"
????????debug="false" scan="true" scanPeriod="30 second">
????<property name="PROJECT" value="iorder" />
????<property name="ROOT" value="logs/${PROJECT}/" />
????<property name="FILESIZE" value="50MB" />
????<property name="MAXHISTORY" value="100" />
????<timestamp key="DATETIME" datePattern="yyyy-MM-dd HH:mm:ss" />
????<appender name="STDOUT" class="ch.qos.logback.core.ConsoleAppender">
????????<encoder charset="utf-8">
????????????<pattern>[%-5level] %d{${DATETIME}} [%thread] %logger{36} - %m%n
????????????</pattern>
????????</encoder>
????</appender>
????<appender name="ERROR" class="ch.qos.logback.core.rolling.RollingFileAppender">
????????<encoder charset="utf-8">
????????????<pattern>[%-5level] %d{${DATETIME}} [%thread] %logger{36} - %m%n
????????????</pattern>
????????</encoder>
????????<filter class="ch.qos.logback.classic.filter.LevelFilter">
????????????<level>ERROR</level>
????????????<onMatch>ACCEPT</onMatch>
????????????<onMismatch>DENY</onMismatch>
????????</filter>
????????<rollingPolicy class="ch.qos.logback.core.rolling.TimeBasedRollingPolicy">
????????????<fileNamePattern>${ROOT}%d/error.%i.log</fileNamePattern>
????????????<maxHistory>${MAXHISTORY}</maxHistory>
????????????<timeBasedFileNamingAndTriggeringPolicy
????????????????????class="ch.qos.logback.core.rolling.SizeAndTimeBasedFNATP">
????????????????<maxFileSize>${FILESIZE}</maxFileSize>
????????????</timeBasedFileNamingAndTriggeringPolicy>
????????</rollingPolicy>
????</appender>
????<appender name="WARN" class="ch.qos.logback.core.rolling.RollingFileAppender">
????????<encoder charset="utf-8">
????????????<pattern>[%-5level] %d{${DATETIME}} [%thread] %logger{36} - %m%n
????????????</pattern>
????????</encoder>
????????<filter class="ch.qos.logback.classic.filter.LevelFilter">
????????????<level>WARN</level>
????????????<onMatch>ACCEPT</onMatch>
????????????<onMismatch>DENY</onMismatch>
????????</filter>
????????<rollingPolicy class="ch.qos.logback.core.rolling.TimeBasedRollingPolicy">
????????????<fileNamePattern>${ROOT}%d/warn.%i.log</fileNamePattern>
????????????<maxHistory>${MAXHISTORY}</maxHistory>
????????????<timeBasedFileNamingAndTriggeringPolicy class="ch.qos.logback.core.rolling.SizeAndTimeBasedFNATP">
????????????????<maxFileSize>${FILESIZE}</maxFileSize>
????????????</timeBasedFileNamingAndTriggeringPolicy>
????????</rollingPolicy>
????</appender>
????<appender name="INFO" class="ch.qos.logback.core.rolling.RollingFileAppender">
????????<encoder charset="utf-8">
????????????<pattern>[%-5level] %d{${DATETIME}} [%thread] %logger{36} - %m%n
????????????</pattern>
????????</encoder>
????????<filter class="ch.qos.logback.classic.filter.LevelFilter">
????????????<level>INFO</level>
????????????<onMatch>ACCEPT</onMatch>
????????????<onMismatch>DENY</onMismatch>
????????</filter>
????????<rollingPolicy class="ch.qos.logback.core.rolling.TimeBasedRollingPolicy">
????????????<fileNamePattern>${ROOT}%d/info.%i.log</fileNamePattern>
????????????<maxHistory>${MAXHISTORY}</maxHistory>
????????????<timeBasedFileNamingAndTriggeringPolicy class="ch.qos.logback.core.rolling.SizeAndTimeBasedFNATP">
????????????????<maxFileSize>${FILESIZE}</maxFileSize>
????????????</timeBasedFileNamingAndTriggeringPolicy>
????????</rollingPolicy>
????</appender>
????<appender name="DEBUG" class="ch.qos.logback.core.rolling.RollingFileAppender">
????????<encoder charset="utf-8">
????????????<pattern>[%-5level] %d{${DATETIME}} [%thread] %logger{36} - %m%n
????????????</pattern>
????????</encoder>
????????<filter class="ch.qos.logback.classic.filter.LevelFilter">
????????????<level>DEBUG</level>
????????????<onMatch>ACCEPT</onMatch>
????????????<onMismatch>DENY</onMismatch>
????????</filter>
????????<rollingPolicy class="ch.qos.logback.core.rolling.TimeBasedRollingPolicy">
????????????<fileNamePattern>${ROOT}%d/debug.%i.log</fileNamePattern>
????????????<maxHistory>${MAXHISTORY}</maxHistory>
????????????<timeBasedFileNamingAndTriggeringPolicy
????????????????????class="ch.qos.logback.core.rolling.SizeAndTimeBasedFNATP">
????????????????<maxFileSize>${FILESIZE}</maxFileSize>
????????????</timeBasedFileNamingAndTriggeringPolicy>
????????</rollingPolicy>
????</appender>
????<appender name="TRACE" class="ch.qos.logback.core.rolling.RollingFileAppender">
????????<encoder charset="utf-8">
????????????<pattern>[%-5level] %d{${DATETIME}} [%thread] %logger{36} - %m%n
????????????</pattern>
????????</encoder>
????????<filter class="ch.qos.logback.classic.filter.LevelFilter">
????????????<level>TRACE</level>
????????????<onMatch>ACCEPT</onMatch>
????????????<onMismatch>DENY</onMismatch>
????????</filter>
????????<rollingPolicy
????????????????class="ch.qos.logback.core.rolling.TimeBasedRollingPolicy">
????????????<fileNamePattern>${ROOT}%d/trace.%i.log</fileNamePattern>
????????????<maxHistory>${MAXHISTORY}</maxHistory>
????????????<timeBasedFileNamingAndTriggeringPolicy
????????????????????class="ch.qos.logback.core.rolling.SizeAndTimeBasedFNATP">
????????????????<maxFileSize>${FILESIZE}</maxFileSize>
????????????</timeBasedFileNamingAndTriggeringPolicy>
????????</rollingPolicy>
????</appender>
????<logger name="org.apache.ibatis" level="INFO" additivity="false" />
????<logger name="org.mybatis.spring" level="INFO" additivity="false" />
????<logger name="com.github.miemiedev.mybatis.paginator" level="INFO" additivity="false" />
????<root level="DEBUG">
????????<appender-ref ref="STDOUT" />
????????<appender-ref ref="DEBUG" />
????????<appender-ref ref="ERROR" />
????????<appender-ref ref="WARN" />
????????<appender-ref ref="INFO" />
????????<appender-ref ref="TRACE" />
????</root>
</configuration>