Here are a few logback.xml examples that are used in my projects, just for sharing.

P.S Tested with Logback 1.2.3

1. Send logs to Console

All logging will be redirected to console.

logback.xml

<configuration>

    <appender name="CONSOLE" class="ch.qos.logback.core.ConsoleAppender">
        <layout class="ch.qos.logback.classic.PatternLayout">
            <Pattern>
                %d{HH:mm:ss.SSS} [%t] %-5level %logger{36} - %msg%n
            </Pattern>
        </layout>
    </appender>

    <logger name="com.mkyong" level="debug" additivity="false">
        <appender-ref ref="CONSOLE"/>
    </logger>

    <root level="error">
        <appender-ref ref="CONSOLE"/>
    </root>

</configuration>

2. Send logs to File + Rotate File

2.1 All logging will be redirected to a file logs/app.log. Furthermore, this log file will be archived daily or when the file size is larger than 10MB.

logback.xml

<configuration>

    <property name="HOME_LOG" value="logs/app.log"/>

    <appender name="FILE-ROLLING" class="ch.qos.logback.core.rolling.RollingFileAppender">
        <file>${HOME_LOG}</file>

        <rollingPolicy class="ch.qos.logback.core.rolling.SizeAndTimeBasedRollingPolicy">
            <fileNamePattern>logs/archived/app.%d{yyyy-MM-dd}.%i.log.gz</fileNamePattern>
            <!-- each archived file, size max 10MB -->
            <maxFileSize>10MB</maxFileSize>
            <!-- total size of all archive files, if total size > 20GB, it will delete old archived file -->
            <totalSizeCap>20GB</totalSizeCap>
            <!-- 60 days to keep -->
            <maxHistory>60</maxHistory>
        </rollingPolicy>

        <encoder>
            <pattern>%d %p %c{1.} [%t] %m%n</pattern>
        </encoder>
    </appender>

    <logger name="com.mkyong" level="debug" additivity="false">
        <appender-ref ref="FILE-ROLLING"/>
    </logger>

    <root level="error">
        <appender-ref ref="FILE-ROLLING"/>
    </root>

</configuration>

2.2 Below SizeAndTimeBasedFNATP example is deprecated, it may still work, but it is better to use the above new SizeAndTimeBasedRollingPolicy example.

logback.xml

<?xml version="1.0" encoding="UTF-8"?>
<configuration>

	<property name="DEV_HOME" value="c:/logs" />

	<appender name="FILE-AUDIT"
		class="ch.qos.logback.core.rolling.RollingFileAppender">
		<file>${DEV_HOME}/debug.log</file>
		<encoder class="ch.qos.logback.classic.encoder.PatternLayoutEncoder">
			<Pattern>
				%d{yyyy-MM-dd HH:mm:ss} - %msg%n
			</Pattern>
		</encoder>

		<rollingPolicy class="ch.qos.logback.core.rolling.TimeBasedRollingPolicy">
			<!-- rollover daily -->
			<fileNamePattern>${DEV_HOME}/archived/debug.%d{yyyy-MM-dd}.%i.log</fileNamePattern>
			<timeBasedFileNamingAndTriggeringPolicy
				class="ch.qos.logback.core.rolling.SizeAndTimeBasedFNATP">
				<maxFileSize>10MB</maxFileSize>
			</timeBasedFileNamingAndTriggeringPolicy>
		</rollingPolicy>

	</appender>

	<logger name="com.mkyong" level="debug"
		additivity="false">
		<appender-ref ref="FILE-AUDIT" />
	</logger>

	<root level="error">
		<appender-ref ref="FILE-AUDIT" />
	</root>

</configuration>

3. Send error logs to email

logback.xml

<configuration>

    <appender name="CONSOLE" class="ch.qos.logback.core.ConsoleAppender">
        <layout class="ch.qos.logback.classic.PatternLayout">
            <Pattern>
                %d{HH:mm:ss.SSS} [%t] %-5level %logger{36} - %msg%n
            </Pattern>
        </layout>
    </appender>

    <appender name="EMAIL" class="ch.qos.logback.classic.net.SMTPAppender">
        <smtpHost>smtp.mailgun.org</smtpHost>
        <smtpPort>25</smtpPort>
        <username>123</username>
        <password>123</password>
        <to>TO_EMAIL</to>
        <to>RO_ANOTHER_EMAIL</to>
        <from>FROM_EMAIL</from>
        <subject>TESTING: %logger{20} - %m</subject>

        <layout class="ch.qos.logback.classic.html.HTMLLayout"/>
    </appender>

    <logger name="com.mkyong" level="error" additivity="false">
        <appender-ref ref="EMAIL"/>
    </logger>

    <root level="error">
        <appender-ref ref="CONSOLE"/>
    </root>

</configuration>

To send email, we need this javax.mail

pom.xml

	<dependency>
		<groupId>com.sun.mail</groupId>
		<artifactId>javax.mail</artifactId>
		<version>1.6.2</version>
	</dependency>

5. Logs Asynchronously

This make logging faster.

logback.xml

<configuration>
   
    <appender name="FILE-ROLLING" class="ch.qos.logback.core.rolling.RollingFileAppender">
        <!-- //... -->
    </appender>

    <appender name="ASYNC" class="ch.qos.logback.classic.AsyncAppender">
        <appender-ref ref="FILE-ROLLING" />
    </appender>

    <root level="debug">
        <appender-ref ref="ASYNC"/>
    </root>

</configuration>

6. SiftingAppender

Send logs to a separate log file, the log file name is defined at runtime, via MDC.

logback.xml

<configuration>

	<property name="DEV_HOME" value="c:/logs" />

	<appender name="FILE-THREAD" class="ch.qos.logback.classic.sift.SiftingAppender">

		<discriminator>
			<key>logFileName</key>
			<defaultValue>head0</defaultValue>
		</discriminator>

	    <sift>

			<appender name="FILE-${logFileName}"
				class="ch.qos.logback.core.rolling.RollingFileAppender">
				<file>${DEV_HOME}/${logFileName}.log</file>
				<encoder class="ch.qos.logback.classic.encoder.PatternLayoutEncoder">
					<Pattern>
						%d{yyyy-MM-dd HH:mm:ss} [%thread] %level %logger{35} - %msg%n
					</Pattern>
				</encoder>

				<rollingPolicy
					class="ch.qos.logback.core.rolling.FixedWindowRollingPolicy">
					<FileNamePattern>${DEV_HOME}/${logFileName}.%i.log.zip</FileNamePattern>
					<MinIndex>1</MinIndex>
					<MaxIndex>10</MaxIndex>
				</rollingPolicy>

				<triggeringPolicy
					class="ch.qos.logback.core.rolling.SizeBasedTriggeringPolicy">
					<MaxFileSize>10MB</MaxFileSize>
				</triggeringPolicy>

			</appender>

	    </sift>
		
	</appender>

	<logger name="com.mkyong.web" level="debug"
		additivity="false">
		<appender-ref ref="FILE-THREAD" />
	</logger>

	<root level="error">
		<appender-ref ref="FILE-THREAD" />
	</root>

</configuration>

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.slf4j.MDC;

//...
public void run() {
 
	MDC.put('logFileName', "head1");
 
	logger.debug("hello");
 
	MDC.remove('logFileName');
 
}
Note
Please refer to this complete Logback SiftingAppender example

7. Set log file name programmatically

Set the log file name ${log.name} programmatically, via System.setProperty

logback.xml

<configuration>

	<property name="USER_HOME" value="/home/mkyong/ant/logs" />

	<appender name="FILE-ENGINE-ERROR" class="ch.qos.logback.core.FileAppender">
		<file>${USER_HOME}/${log.name}.error</file>
		<encoder>
			<pattern>%d{yyyy-MM-dd HH:mm:ss} [%thread] %-5level %logger{36} - %msg%n</pattern>
		</encoder>
	</appender>
	
	<appender name="FILE-ENGINE" class="ch.qos.logback.core.FileAppender">
		<file>${USER_HOME}/${log.name}.log</file>
		<encoder>
			<pattern>%d{yyyy-MM-dd HH:mm:ss} [%thread] %-5level %logger{35} - %msg%n</pattern>
		</encoder>
	</appender>

	<logger name="com.mkyong.core" level="debug" additivity="false">
		<appender-ref ref="FILE-ENGINE" />
	</logger>

	<root level="error">
		<appender-ref ref="FILE-ENGINE-ERROR" />
	</root>

</configuration>
TestRunApp.java

package com.mkyong.core;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

public class TestRunApp {

    //No static, else log.name.IS_UNDEFINED.log
    private final Logger logger = LoggerFactory.getLogger(TestRunApp.class);

	public static void main(String[] args) {

		//Set this before the logger start.
		System.setProperty("log.name", "abcdefg");

		TestRunApp obj = new TestRunApp();
		obj.start();

	}

	private void start() {

        logger.debug("------ Starting Ant------");
     	//...
	}

}

Output


Debug log file path
/home/mkyong/ant/logs/abcdefg.log

Error log file path
/home/mkyong/ant/logs/abcdefg.error
Note
Please refer to this complete example Logback – Set log file name programmatically

References