How to clear log file before executing spring boot app? - spring-boot

Question

I have been using the default spring logging configuration where I only specify filename in the application.properties file.
logging.file.name=app.log
But this by default appends logs when I start the application from cmd line "java -jar abc.jar"
I tried to search for the property which clears the file before starting application every time but couldn't find it. How should I clear the log file before starting the app?

Answer 1

Spring Boot uses Logback framework as as a default Logger.
You can use environnement variable via application.properties file to set some logging properties but logback xml configuration provides more powerfull features.
When a file in the classpath has one of the following names, Spring Boot will automatically load it over the default configuration:
logback-spring.xml
logback.xml
logback-spring.groovy
logback.groovy
So You can just put the code snippet below in src/main/resources/logback-spring.xml file
<?xml version="1.0" encoding="UTF-8"?>
<configuration>
<appender name="Console"
class="ch.qos.logback.core.ConsoleAppender">
<layout class="ch.qos.logback.classic.PatternLayout">
<Pattern>
%black(%d{ISO8601}) %highlight(%-5level) [%blue(%t)] %yellow(%C{1.}): %msg%n%throwable
</Pattern>
</layout>
</appender>
<appender name="FILE" class="ch.qos.logback.core.FileAppender">
<file>app.log</file>
<append>false</append>
<encoder>
<pattern>%-4relative [%thread] %-5level %logger{35} - %msg%n</pattern>
</encoder>
</appender>
<!-- LOG everything at INFO level -->
<root level="info">
<appender-ref ref="FILE" />
<appender-ref ref="Console" />
</root>
</configuration>
The line <append>false</append> does the job.
if you wanna log more information than those avaible with the encoder pattern <pattern>%-4relative [%thread] %-5level %logger{35} - %msg%n</pattern> please check logback documention https://logback.qos.ch/manual/layouts.html#logback-access