Read environment variables from logback configuration file

Pablo_Fernandez_7595 0
Viewed 115771

I have this logback.xml file:

<configuration debug="true" scan="true" scanPeriod="60 seconds">

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

  <appender name="FILE" class="ch.qos.logback.core.rolling.RollingFileAppender">
    <File>${MY_HOME}/logs/mylog.log</File>

    <rollingPolicy class="ch.qos.logback.core.rolling.TimeBasedRollingPolicy">
      <FileNamePattern>logs/my.%d{yyyy-MM-dd}.log</FileNamePattern>
      <MaxHistory>30</MaxHistory>
    </rollingPolicy>

    <layout class="ch.qos.logback.classic.PatternLayout">
      <Pattern>%d{HH:mm:ss.SSS} [%thread] %-5level - %msg%n</Pattern>
    </layout>

  </appender> 

  <root level="TRACE">
    <appender-ref ref="FILE"/>
  </root>

</configuration>

And ${MY_HOME} is a defined system variable (echo $MY_HOME on linux shows the correct path).

The thing is that logback doesnt seem to read it properly, it stores the logs under MY_HOME_IS_UNDEFINED/logs/my.log

What am I doing wrong? Thanks a lot!

EDIT: I made a mistake and put OSC_HOME where I really meant MY_HOME. Sorry about that

logback environment-variables logging java
6 Answers

Contrary to what the others have said, the logback documentation explicitly states that "During substitution, properties are looked up in the local scope first, in the context scope second, in the system properties scope third, and in the OS environment fourth and last". So if the property is defined in the environment, logback will find it.

I was having the same issue when running my project in Eclipse. If that's the issue you're having, it can be fixed by going to Run Configurations -> Environment and adding MY_HOME to the environment variables.

Not really sure why it isn't loading the native environment by default. There's even an option called "Append environment to native environment" which doesn't seem to have any effect for me.

user_8367380

You perhaps mean MY_HOME. In your config file there is reference for OSC_HOME. See Variable substitution rules of Logback for details.

You can pass environment variable as a Java System property and then Logback will perform the variable substitution. You can pass this as JVM option in your command line. For example:

java -DMY_HOME=${MY_HOME} -cp ... MainClass

Or You can define MY_HOME in your config file itself.

<configuration debug="true" scan="true" scanPeriod="60 seconds">
  <property name="MY_HOME" value="/home/my" />
  <appender name="FILE" class="ch.qos.logback.core.rolling.RollingFileAppender">
    <File>${MY_HOME}/logs/mylog.log</File>
  </appender> 
</configuration>
user_2231960

Things are actually working as designed: logback doesn't read environment variables at all when doing variable substitution. Quoting the documentation:

The value of the substituted variable can be defined in the configuration file itself, in an external properties file or as a system property.

So, either use one of the mentioned solutions or get OSC_HOME_IS_UNDEFINED :)

user_706040
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