Is it possible to suppress only Warn messages in Log4j2 while allowing all others

Question

I am using log4j2 to log messages in console and in a file. I am getting a lot of Warn message which I do not want. I only want to see Debug and other messages. is it possib

Answer 1

You can use the LevelRangeFilter to reject the log events.

Here's a simple class that generates some logs:

import org.apache.logging.log4j.LogManager;
import org.apache.logging.log4j.Logger;

public class SomeClass {

    private static final Logger log = LogManager.getLogger();   

    public static void main(String[] args){

        if(log.isDebugEnabled())
            log.debug("This is some debug!");
        log.info("Here's some info!");
        log.warn("Warning will be rejected.");
        log.error("Some error happened!");
    }
}

Here's a basic configuration that just sends all events to console:

<?xml version="1.0" encoding="UTF-8"?>
<Configuration status="WARN">
    <Appenders>
        <Console name="Console" target="SYSTEM_OUT">
            <PatternLayout pattern="%d{HH:mm:ss.SSS} [%t] %-5level %logger{36} - %msg%n" />
        </Console>
    </Appenders>

    <Loggers>
        <Root level="ALL">
            <AppenderRef ref="Console" />
        </Root>
    </Loggers>
</Configuration>

The output generated by the above is:

21:08:42.215 [main] DEBUG example.SomeClass - This is some debug!
21:08:42.217 [main] INFO  example.SomeClass - Here's some info!
21:08:42.217 [main] WARN  example.SomeClass - Warning will be rejected.
21:08:42.217 [main] ERROR example.SomeClass - Some error happened!

Now we add the LevelRangeFilter to the Console appender:

    <Console name="Console" target="SYSTEM_OUT">
        <PatternLayout pattern="%d{HH:mm:ss.SSS} [%t] %-5level %logger{36} - %msg%n" />
        <LevelRangeFilter minLevel="WARN" maxLevel="WARN" onMatch="DENY" onMismatch="NEUTRAL"/>
    </Console>

Now the output is:

21:15:26.987 [main] DEBUG example.SomeClass - This is some debug!
21:15:26.989 [main] INFO  example.SomeClass - Here's some info!
21:15:26.989 [main] ERROR example.SomeClass - Some error happened!

As you can see the WARN message is not logged to console.

Answer 2

Try threshold filters as follows:

<Configuration status="error">
    <Appenders>
        <Console name="Console" target="SYSTEM_OUT">
          <Filters>
                 <!-- Accept error and fatal messages -->
                 <ThresholdFilter level="error"  onMatch="ACCEPT"   onMismatch="NEUTRAL"/>

                 <!-- Reject Warn messages -->
                 <ThresholdFilter level="warn"  onMatch="DENY"   onMismatch="NEUTRAL"/>

                 <!-- This filter accepts debug, trace, info, error, fatal  -->
                 <ThresholdFilter level="trace"  onMatch="ACCEPT" onMismatch="DENY"/>
            </Filters>      
            <PatternLayout pattern="[%d{DEFAULT}][%5p][%t][%c{1}] - %m%n" />
        </Console>
        <File name="MyFile" fileName="logs/java.log" immediateFlush="false" append="true">
          <Filters>
                 <!-- Accept error and fatal messages -->
                 <ThresholdFilter level="error"  onMatch="ACCEPT"   onMismatch="NEUTRAL"/>

                 <!-- Reject Warn messages -->
                 <ThresholdFilter level="warn"  onMatch="DENY"   onMismatch="NEUTRAL"/>

                 <!-- This filter accepts debug, trace, info, error, fatal  -->
                 <ThresholdFilter level="trace"  onMatch="ACCEPT" onMismatch="DENY"/>
            </Filters>      
            <PatternLayout pattern="[%d{DEFAULT}][%5p][%t][%c{1}] - %m%n"/>
        </File>
    </Appenders>
    <Loggers>
        <Root level="debug">
            <AppenderRef ref="Console" />
            <AppenderRef ref="MyFile"/>
        </Root>
    </Loggers>
</Configuration>