73.1 Configure Logback for logging

If you put a logback.xml in the root of your classpath it will be picked up from there (or logback-spring.xml to take advantage of the templating features provided by Boot). Spring Boot provides a default base configuration that you can include if you just want to set levels, e.g.

<?xml version="1.0" encoding="UTF-8"?>
<configuration>
    <include resource="org/springframework/boot/logging/logback/base.xml"/>
    <logger name="org.springframework.web" level="DEBUG"/>
</configuration>

If you look at that base.xml in the spring-boot jar, you will see that it uses some useful System properties which the LoggingSystem takes care of creating for you. These are:

• ${PID} the current process ID.
• ${LOG_FILE} if logging.file was set in Boot’s external configuration.
• ${LOG_PATH} if logging.path was set (representing a directory for log files to live in).
• ${LOG_EXCEPTION_CONVERSION_WORD} if logging.exception-conversion-word was set in Boot’s external configuration.

Spring Boot also provides some nice ANSI colour terminal output on a console (but not in a log file) using a custom Logback converter. See the default base.xml configuration for details.

If Groovy is on the classpath you should be able to configure Logback with logback.groovy as well (it will be given preference if present).

73.1.1 Configure logback for file only output

If you want to disable console logging and write output only to a file you need a custom logback-spring.xml that imports file-appender.xml but not console-appender.xml:

<?xml version="1.0" encoding="UTF-8"?>
<configuration>
    <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/file-appender.xml" />
    <root level="INFO">
        <appender-ref ref="FILE" />
    </root>
</configuration>

You also need to add logging.file to your application.properties:

logging.file=myapplication.log