由于SpringBoot默认整合了Logback依赖，因此不需要额外地添加依赖
</dependencies>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter</artifactId>
</dependency>
</dependencies>
SpringBoot提供了logback的默认配置，位于spring-boot.jar的org/springframework/boot/logging/logback/base.xml，包含配置如下：可以看见default.xml提供了默认转换规则、全局属性以及logger的配置；console-appender.xml中定义了console输出的具体配置；在file-appender.xml中定义了文件输出的具体配置。
base.xml：
<?xml version="1.0" encoding="UTF-8"?>
<included>
<include resource="org/springframework/boot/logging/logback/defaults.xml" />
<property name="LOG_FILE" value="${LOG_FILE:-${LOG_PATH:-${LOG_TEMP:-${java.io.tmpdir:-/tmp}}}/spring.log}"/>
<include resource="org/springframework/boot/logging/logback/console-appender.xml" />
<include resource="org/springframework/boot/logging/logback/file-appender.xml" />
<root level="INFO">
<appender-ref ref="CONSOLE" />
<appender-ref ref="FILE" />
</root>
</included>
default.xml配置如下:
<?xml version="1.0" encoding="UTF-8"?>
<included>
<conversionRule conversionWord="clr" converterClass="org.springframework.boot.logging.logback.ColorConverter" />
<conversionRule conversionWord="wex" converterClass="org.springframework.boot.logging.logback.WhitespaceThrowableProxyConverter" />
<conversionRule conversionWord="wEx" converterClass="org.springframework.boot.logging.logback.ExtendedWhitespaceThrowableProxyConverter" />
<property name="CONSOLE_LOG_PATTERN" value="${CONSOLE_LOG_PATTERN:-%clr(%d{${LOG_DATEFORMAT_PATTERN:-yyyy-MM-dd HH:mm:ss.SSS}}){faint} %clr(${LOG_LEVEL_PATTERN:-%5p}) %clr(${PID:- }){magenta} %clr(---){faint} %clr([%15.15t]){faint} %clr(%-40.40logger{39}){cyan} %clr(:){faint} %m%n${LOG_EXCEPTION_CONVERSION_WORD:-%wEx}}"/>
<property name="FILE_LOG_PATTERN" value="${FILE_LOG_PATTERN:-%d{${LOG_DATEFORMAT_PATTERN:-yyyy-MM-dd HH:mm:ss.SSS}} ${LOG_LEVEL_PATTERN:-%5p} ${PID:- } --- [%t] %-40.40logger{39} : %m%n${LOG_EXCEPTION_CONVERSION_WORD:-%wEx}}"/>
<logger name="org.apache.catalina.startup.DigesterFactory" level="ERROR"/>
<logger name="org.apache.catalina.util.LifecycleBase" level="ERROR"/>
<logger name="org.apache.coyote.http11.Http11NioProtocol" level="WARN"/>
<logger name="org.apache.sshd.common.util.SecurityUtils" level="WARN"/>
<logger name="org.apache.tomcat.util.net.NioSelectorPool" level="WARN"/>
<logger name="org.eclipse.jetty.util.component.AbstractLifeCycle" level="ERROR"/>
<logger name="org.hibernate.validator.internal.util.Version" level="WARN"/>
</included>
console-appender.xml：
<?xml version="1.0" encoding="UTF-8"?>
<included>
<appender name="CONSOLE" class="ch.qos.logback.core.ConsoleAppender">
<encoder>
<pattern>${CONSOLE_LOG_PATTERN}</pattern>
</encoder>
</appender>
</included>
file-appender.xml
<?xml version="1.0" encoding="UTF-8"?>
<included>
<appender name="FILE"
class="ch.qos.logback.core.rolling.RollingFileAppender">
<encoder>
<pattern>${FILE_LOG_PATTERN}</pattern>
</encoder>
<file>${LOG_FILE}</file>
<rollingPolicy class="ch.qos.logback.core.rolling.SizeAndTimeBasedRollingPolicy">
<fileNamePattern>${LOG_FILE}.%d{yyyy-MM-dd}.%i.gz</fileNamePattern>
<maxFileSize>${LOG_FILE_MAX_SIZE:-10MB}</maxFileSize>
<maxHistory>${LOG_FILE_MAX_HISTORY:-0}</maxHistory>
</rollingPolicy>
</appender>
</included>
除了使用SpringBoot默认的配置，还可以自定义logback配置文件，并且放在项目类路径下就能生效。具体的配置文件如下：下面的配置文件还使用了springProfile对不同运行环境使用不同的日志输出，这是SpringBoot对logback特别提供的。
logback-spring.xml
<?xml version="1.0" encoding="UTF-8"?>
<configuration scan="true">
<!--定义上下文名称-->
<contextName>logback-demo</contextName>
<!--引用了默认配置default.xml-->
<include resource="org/springframework/boot/logging/logback/defaults.xml"/>
<!--定义变量LOG_FILE FILE_LOG_PATTERN-->
<property name="LOG_FILE" value="D:/"/>
<property name="FILE_LOG_PATTERN" value="${FILE_LOG_PATTERN:-%d{${LOG_DATEFORMAT_PATTERN:-yyyy-MM-dd HH:mm:ss.SSS}} ${LOG_LEVEL_PATTERN:-%5p} ${PID:- } --- [%t] %-40.40logger{39} : %m%n${LOG_EXCEPTION_CONVERSION_WORD:-%wEx}}"/>
<!--springboot 支持springProfile 针对不同环境可以配置不同的输出-->
<springProfile name="default">
<include resource="org/springframework/boot/logging/logback/console-appender.xml"/>
<logger name="com.mamba.logback" level="DEBUG"/>
<root level="info">
<appender-ref ref="CONSOLE"/>
</root>
</springProfile>
<!--配置dev环境输出配置-->
<springProfile name="dev">
<appender name="CONSOLE" class="ch.qos.logback.core.ConsoleAppender">
<encoder>
<pattern>"${CONSOLE_LOG_PATTERN:-%clr(%d{${LOG_DATEFORMAT_PATTERN:-yyyy-MM-dd HH:mm:ss}}){faint}
%clr(${LOG_LEVEL_PATTERN:-%5p}) %clr(${PID:- }){magenta} %clr(---){faint} %clr([%15.15t]){faint}
%clr(%-40.40logger{39}){red} %clr(:){faint} %m%n${LOG_EXCEPTION_CONVERSION_WORD:-%wEx}}
</pattern>
</encoder>
</appender>
<root level="info">
<appender-ref ref="CONSOLE"/>
</root>
</springProfile>
<!--配置prod环境输出配置-->
<springProfile name="prod">
<include resource="org/springframework/boot/logging/logback/console-appender.xml"/>
<appender name="FILE"
class="ch.qos.logback.core.rolling.RollingFileAppender">
<encoder>
<pattern>${FILE_LOG_PATTERN}</pattern>
</encoder>
<file>${LOG_FILE}springboot.log</file>
<rollingPolicy class="ch.qos.logback.core.rolling.SizeAndTimeBasedRollingPolicy">
<fileNamePattern>${LOG_FILE}.%d{yyyy-MM-dd}.%i.gz</fileNamePattern>
<maxFileSize>${LOG_FILE_MAX_SIZE:-10MB}</maxFileSize>
<maxHistory>${LOG_FILE_MAX_HISTORY:-0}</maxHistory>
</rollingPolicy>
</appender>
<logger name="com.mamba.logback" level="INFO"/>
<root level="DEBUG">
<appender-ref ref="CONSOLE"/>
<appender-ref ref="FILE"/>
</root>
</springProfile>
</configuration>
需要注意的是，SpringBoot本身提供的日志相关配置属性是独立于logback的，如果要测试这些属性，需要将logback-spring移除，不然SpringBoot会覆盖掉这些属性。