Configure logback with HOCON

application.conf

app {
  name: logstash-hocon-gist
}

gistfile1.txt

<configuration>
  
  <!--read properties from application.conf-->
  <newRule pattern="*/load" actionClass="mypackage.LoadFromApplicationConf"/>
  <load key="app.name" as="APP_NAME"/>
  
  <appender name="application" class="ch.qos.logback.core.rolling.RollingFileAppender">
    <file>logs/${APP_NAME}.log</file>
    <rollingPolicy class="ch.qos.logback.core.rolling.TimeBasedRollingPolicy">
      <fileNamePattern>logs/${APP_NAME}.%d{yyyy-MM-dd}.log.gz</fileNamePattern>
      <maxHistory>10</maxHistory>
    </rollingPolicy>
    <encoder>
      <pattern>%date{MM/dd HH:mm:ss} %-5level[%thread] %logger{1} - %msg%n</pattern>
    </encoder>
  </appender>
  
  <root level="warn">
    <appender-ref ref="application"/>
  </root>
  
</configuration>

LoadFromApplicationConf.scala

package mypackage

import ch.qos.logback.core.joran.action.Action
import ch.qos.logback.core.joran.spi.InterpretationContext
import com.typesafe.config.ConfigFactory
import org.xml.sax.Attributes

/**
 * Make properties defined in application.conf available to logback
 */
class LoadFromApplicationConf extends Action {
  val config = ConfigFactory.load
  override def begin(ic: InterpretationContext, body: String, attributes: Attributes): Unit = {
    ic.addSubstitutionProperty(attributes.getValue("as"), config.getString(attributes.getValue("key")))
  }
  override def end(ic: InterpretationContext, body: String): Unit = ()
}