Conditionally Print Stack Trace on Error Page Depending on Log Level using Facelets, Seam, and Logback

Question

I would like to print the stack trace for the exception that was caught by pages.xml, but I only want to do so if the most granular logging level is more granular than warn. This way, testers can copy/paste the stack trace, but end users will never see it.

Environment details:

• IBM WebSphere Application Server 7 (logging level details)
• JBoss Seam 2.2.0.GA
• JSF Facelets 1.1.15
• Logback 0.9.21
  • SLF4J 1.6.0
    • Log4j over SLF4J
    • JCL over SLF4J

Here's how exceptions are currently being handled...

From pages.xml:

<?xml version="1.0" encoding="UTF-8"?>
<pages xmlns="http://jboss.com/products/seam/pages" 
        xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
        xsi:schemaLocation="http://jboss.com/products/seam/pages http://jboss.com/products/seam/pages-2.2.xsd"&gt;

    <!-- ... -->

    <exception class="javax.faces.application.ViewExpiredException">
        <end-conversation />
        <redirect view-id="/exceptionSessionTimeout.xhtml" />
    </exception>

    <!--
         Prevent the Facelets error page from appearing.
         This is where I want to conditionally print the stack trace.
         Currently it's more or less just a generic error page.
    -->
    <exception>
        <end-conversation />
        <redirect view-id="/exception.xhtml" />
    </exception>
</pages>

From web.xml:

<?xml version="1.0" encoding="UTF-8"?>
<web-app id="WebApp_ID" version="2.5" 
        xmlns="http://java.sun.com/xml/ns/javaee" 
        xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
        xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd"&gt;

    <!-- ... -->

    <!-- Fallback static HTML page -->
    <error-page>
        <exception-type>java.lang.Exception</exception-type>
        <location>/unhandledException.html</location>
    </error-page>
</web-app>

From logback.xml:

<?xml version="1.0" encoding="UTR-8"?>
<configuration scan="true">
    <appender name="CONSOLE" class="ch.qos.logback.core.ConsoleAppender">
        <encoder>
            <pattern>[%date] [%thread] [%level] [%mdc] [%logger:%method:%line]: %msg%n</pattern>
        </encoder>
    </appender>

    <appender name="FILE" class="ch.qos.logback.core.rolling.RollingFileAppender">
        <file>/path/to/app-logs-dir/AppName.log</file>
        <rollingPolicy class="ch.qos.logback.core.rolling.TimeBasedRollingPolicy">
            <fileNamePattern>/path/to/app-logs-dir/AppName.%d{yyyy-MM-dd-a}.gz</fileNamePattern>
        </rollingPolicy>
        <encoder>
            <pattern>[%date] [%thread] [%level] [%mdc] [%logger:%method:%line]: %msg%n</pattern>
        </encoder>
    </appender>

    <logger name="com.example" level="trace" />
    <logger name="com.example.auth" level="error" />

    <root level="warn">
        <appender-ref ref="FILE" />
        <appender-ref ref="CONSOLE" />
    </root>
</configuration>

With the ideal solution to this problem, this would cause a stack trace to be printed on /error.xhtml (from pages.xml):

<logger name="com.example" level="trace" />

Whereas this would not:

<logger name="com.example" level="warn" />

Using Facelets with Seam, is there a way to determine Logback's log levels?