<appender name="NEW-APPENDER-FOR-JETTY" class="ch.qos.logback.core.rolling.RollingFileAppender">

    <file>../log/jetty_ERR_WARN.log</file>

    <rollingPolicy class="ch.qos.logback.core.rolling.FixedWindowRollingPolicy">

        <fileNamePattern>../log/jetty_ERR_WARN_%i.log</fileNamePattern>

        <minIndex>1</minIndex>

        <maxIndex>3</maxIndex>

    </rollingPolicy>

    <triggeringPolicy class="ch.qos.logback.core.rolling.SizeBasedTriggeringPolicy">

        <maxFileSize>200KB</maxFileSize>

    </triggeringPolicy>

    <encoder>

        <pattern>%d{yyyy-MM-dd HH:mm:ss.SSS} %-5level [%thread] %logger{36} - %msg%n</pattern>

    </encoder>

</appender>

  

<logger name="org.eclipse.jetty" additivity="false"> ​<!--additivity makes sure its using only this appender and not other parent appenders-->​

    <level value="WARN" />  <!-- Will include warn and error logs -->

    <appender-ref ref="NEW-APPENDER-FOR-JETTY"/>   

</logger> 

Thanks,

Nazila