How do I filter certain lines from a log4j stack trace?

Use this filtering layout log4j add-on: http://www.openmindlab.com/lab/tools/openutilslog4j/layout.html

They have an example with log4j.xml on that page. Just use the it.openutils.log4j.FilteredPatternLayout instead of the log4j PatternLayout, and then put some entries like

    <param name="Filter" value="net.sf.cglib"/>
    <param name="Filter" value="org.springframework"/>

below.