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7.12.4. Using XML for exception handling

Since annotations cannot be added to all exception classes, Seam also lets us specify this functionality in pages.xml. 
<pages>
  <exception class="javax.persistence.EntityNotFoundException">
    <http-error error-code="404"/>
  </exception>
  
  <exception class="javax.persistence.PersistenceException">
    <end-conversation/>
    <redirect view-id="/error.xhtml">
      <message>Database access failed</message>
    </redirect>
  </exception>
  
  <exception>
    <end-conversation/>
    <redirect view-id="/error.xhtml">
      <message>Unexpected failure</message>
    </redirect>
  </exception>   
</pages>
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The final <exception> declaration does not specify a class, and acts as catch-all for any exception without specified handling via annotations or in pages.xml.
You can also use EL to specify the view-id to redirect to.
You can also access the handled exception instance through EL. Seam places it in the conversation context. For example, to access the exception message: 
...
  throw new AuthorizationException("You are not allowed to do this!");

<pages>
  <exception class="org.jboss.seam.security.AuthorizationException">
    <end-conversation/>
    <redirect view-id="/error.xhtml">
      <message severity="WARN">
        #{org.jboss.seam.handledException.message}
      </message>
    </redirect>
  </exception>
</pages>
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org.jboss.seam.handledException holds the nested exception that was handled by an exception handler. The outermost (wrapper) exception is also available as org.jboss.seam.caughtException.

7.12.4.1. Suppressing exception logging
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For the exception handlers defined in pages.xml, it is possible to declare the level at which the exception will be logged, or to suppress exception logging altogether. The log and log-level attributes are used to control exception logging. No log message will be generated when the specified exception occurs when log="false" is set, as shown here: 
<exception class="org.jboss.seam.security.NotLoggedInException" 
           log="false"> 
  <redirect view-id="/register.xhtml">
    <message severity="warn">
      You must be a member to use this feature
    </message> 
  </redirect> 
</exception>
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If the log attribute is not specified, then it defaults to true — that is, the exception will be logged. Alternatively, you can specify the log-level to control the level at which the exception will be logged: 
<exception class="org.jboss.seam.security.NotLoggedInException" 
           log-level="info"> 
  <redirect view-id="/register.xhtml"> 
    <message severity="warn">
      You must be a member to use this feature
    </message> 
  </redirect> 
</exception>
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The acceptable values for log-level are: fatal, error, warn, info, debug, and trace. If the log-level is not specified, or if an invalid value is configured, log-level will default to error.
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