Is there a way in logback.xml to specify file log destination through classpath:, without absolute path?

Question

I've in my logback.xml configuration file this appender:

<appender name="FILE"
            class="ch.qos.logback.core.rolling.RollingFileAppender">
    <file>classpath:addressbookLog.log</file>
    <encoder class="ch.qos.logback.classic.encoder.PatternLayoutEncoder">
      <Pattern>%d{dd MMM yyyy;HH:mm:ss} %-5level %logger{36} - %msg%n
      </Pattern>
    </encoder>
    <rollingPolicy class="ch.qos.logback.core.rolling.FixedWindowRollingPolicy">
      <FileNamePattern>classpath:addressbookLog.%i.log.zip</FileNamePattern>
      <MinIndex>1</MinIndex>
      <MaxIndex>10</MaxIndex>
    </rollingPolicy>

    <triggeringPolicy
      class="ch.qos.logback.core.rolling.SizeBasedTriggeringPolicy">
      <MaxFileSize>2MB</MaxFileSize>
    </triggeringPolicy>
  </appender>

so that I specify path to file in which to print logs in a relative way through classpath, but it doesn't work, no file addressbookLog.log is created and written. It only works with absolute paths like /home/andrea/.../resources/addressbookLog.log Have you any ideas on how to make it work with classpath?

Answer 1

The Chapter 3: Logback configuration: Variable substitution told us the various ways to refer to the variable defined outside, e.g. system properties and classpath.

The significant configuration is creating a separate file that will contain all the variables. We can make a reference to a resource on the class path instead of a file as well. e.g.

The logback.xml

<configuration>

  <property resource="resource1.properties" />

  <appender name="FILE" class="ch.qos.logback.core.FileAppender">
     <!-- Here we can refer to the variable 
      defined at the resource1.properties -->
     <file>${USER_HOME}/myApp.log</file>
     <encoder>
       <pattern>%msg%n</pattern>
     </encoder>
   </appender>

   <root level="debug">
     <appender-ref ref="FILE" />
   </root>
</configuration>

The external properties file (resource1.properties)

USER_HOME=/path/to/somewhere

Please note that the resource1.properties is a resource which available at the classpath.

You may refer to the full version at Chapter 3: Logback configuration: Variable substitution. I hope this may help.