log4j: different category priority than appender threshold

Question

I've been trying to get this simple use case to work but can't: Define a default Threshold of INFO on a FILE Appender, but define a category with DEBUG level. This is a jboss 4.2.1.GA log4j.xml file that I am using where I just want to log java.sql calls.

   <appender name="SQL_FILE" class="org.jboss.logging.appender.DailyRollingFileAppender">
      <errorHandler class="org.jboss.logging.util.OnlyOnceErrorHandler"/>
      <param name="File" value="${jboss.server.log.dir}/sql.log"/>
      <param name="Append" value="false"/>
      <param name="Threshold" value="INFO"/>

      <param name="DatePattern" value="'.'yyyy-MM-dd"/>

      <layout class="org.apache.log4j.PatternLayout">
         <param name="ConversionPattern" value="%d %-5p [%c] %C %m%n"/>
      </layout>
   </appender>

  <category name="java.sql">
    <priority value="DEBUG"/>
    <appender-ref ref="SQL_FILE"/>
  </category>

   <root>
      <appender-ref ref="SQL_FILE"/>
   </root>

Instead of logging just java.sql it logs INFO and above and does not include any java.sql information. If there is no easy solution then I am left with setting the appender Threshold to DEBUG and turning off all logging for the multiple categories that get included, which seems a waste of time.

I tried the following but couldn't get it to work: Configuring multiple log files in log4j while using categories.

Solution

I soon found the solution. Basically the use case is described in the jboss wiki here: http://docs.jboss.org/process-guide/en/html/logging.html Section 10.3.5 Redirecting Category Output. This blog article was helpful as well: ptth://ourcraft.wordpress.com/2008/10/23/customizing-log4j-logging-on-jboss/#comment-796.

Ultimately here is what I used that worked:

   <appender name="SQL_FILE" class="org.jboss.logging.appender.DailyRollingFileAppender">
      <errorHandler class="org.jboss.logging.util.OnlyOnceErrorHandler"/>
      <param name="File" value="${jboss.server.log.dir}/sql.log"/>
      <param name="Append" value="false"/>

      <param name="DatePattern" value="'.'yyyy-MM-dd"/>

      <layout class="org.apache.log4j.PatternLayout">
         <param name="ConversionPattern" value="%d %-5p [%c] %C %m%n"/>
      </layout>

   </appender>

<category name="java.sql.Connection"  additivity="false">
    <priority value="DEBUG"/>
    <appender-ref ref="SQL_FILE"/>
</category>  

   <root>
      <appender-ref ref="CONSOLE"/>
      <appender-ref ref="FILE"/>
   </root>

Note that you do not want to define the SQL_FILE appender in root; for some reason. That was the final piece.