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

Answer: 
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](http://mvnrepository.com/artifact/org.codehaus.janino/janino) to handle the expression parsing.
This is an additional example of the response of [@palacsint](https://stackoverflow.com/a/7368873/984838) that apply when the error is not an exception using [JaninoEventEvaluator](https://logback.qos.ch/manual/filters.html#JaninoEventEvaluator):

```xml
<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>

```