How do I not log a particular type of Exception in Logback?

Question

How do I configure Logback to ignore logging on exceptions of a particular type?

Answer 1

This is an additional example of the response of @palacsint that apply when the error is not an exception using JaninoEventEvaluator:

<filter class="ch.qos.logback.core.filter.EvaluatorFilter">
  <evaluator>
    <expression>logger.equals("org.docx4j.fonts.GlyphCheck") &amp;&amp; level == ERROR</expression>
  </evaluator>
  <onMatch>DENY</onMatch>
</filter>

Answer 2

You can do it with a simple EvaluatorFilter:

<filter class="ch.qos.logback.core.filter.EvaluatorFilter">
    <evaluator>
        <expression>java.lang.RuntimeException.class.isInstance(throwable)</expression>
    </evaluator>
    <onMatch>DENY</onMatch>
</filter>

Please note that you need the following dependency in your pom.xml as well:

<dependency>
    <groupId>org.codehaus.janino</groupId>
    <artifactId>janino</artifactId>
    <version>2.5.16</version>
</dependency>

Another possible solution is a custom Filter implementation:

import ch.qos.logback.classic.spi.ILoggingEvent;
import ch.qos.logback.classic.spi.IThrowableProxy;
import ch.qos.logback.classic.spi.ThrowableProxy;
import ch.qos.logback.core.filter.Filter;
import ch.qos.logback.core.spi.FilterReply;

public class SampleFilter extends Filter<ILoggingEvent> {

    private Class<?> exceptionClass;

    public SampleFilter() {
    }

    @Override
    public FilterReply decide(final ILoggingEvent event) {
        final IThrowableProxy throwableProxy = event.getThrowableProxy();
        if (throwableProxy == null) {
            return FilterReply.NEUTRAL;
        }

        if (!(throwableProxy instanceof ThrowableProxy)) {
            return FilterReply.NEUTRAL;
        }

        final ThrowableProxy throwableProxyImpl = 
            (ThrowableProxy) throwableProxy;
        final Throwable throwable = throwableProxyImpl.getThrowable();
        if (exceptionClass.isInstance(throwable)) {
            return FilterReply.DENY;
        }

        return FilterReply.NEUTRAL;
    }

    public void setExceptionClassName(final String exceptionClassName) {
        try {
            exceptionClass = Class.forName(exceptionClassName);
        } catch (final ClassNotFoundException e) {
            throw new IllegalArgumentException("Class is unavailable: "
                    + exceptionClassName, e);
        }
    }
}

With a proper config:

<filter class="hu.palacsint.logbacktest.SampleFilter">
    <exceptionClassName>java.lang.Exception</exceptionClassName>
</filter>

In a TurboFilter you get the thrown Throwable instance directly, so you can call the isInstance method without manually casting the IThrowableProxy to ThrowableProxy.

Further documentation

Answer 3

This question is 5 years old, but I'm supplying the solution I found just to keep it up to date.

I found a solution in the offical docs: http://logback.qos.ch/manual/layouts.html

For my particular situation, which is a 17 year old web site running plain old servlets (ah, the days), the servlet is now throwing an exception if the user was not logged in. So here's my code snippets:

Servlet

  try {
    InvalidLoginException.throwIfBadLogin(webUser);

    // main logic here

  } catch (InvalidLoginException e) {
    throw e;
  } catch (Throwable t) {
    log.error(t);
    throw new UnhandledException(t);
  }

web.xml

<error-page>
    <exception-type>com.mycompany.servlet.exception.InvalidLoginException</exception-type>
    <location>/servlet/Login</location>
</error-page>

From the setup above, I didn't want to log this exception as it's not really an exception, but rather a break in logic to redirect to login.

So, the start of my logback.xml file is this:

  <configuration packagingData="true" scan="true" debug="true" scanPeriod="30 seconds">
    <evaluator name="InvalidLoginExceptionSuppressor">
      <expression>throwable != null &amp;&amp; throwable instanceof com.mycompany.servlet.exception.InvalidLoginException</expression>
    </evaluator>

and further down in the logback.xml file, my appenders:

  <appender name="STDOUT" class="ch.qos.logback.core.ConsoleAppender">
    <encoder>
      <pattern>%d{MM-dd HH:mm:ss.SSS} %-5level %logger{36} - %msg %ex{full,InvalidLoginExceptionSuppressor}%n</pattern>
      <immediateFlush>false</immediateFlush>
    </encoder>

Also note, in order to this work, I had to include janino to handle the expression parsing.