/**
* Logback: the reliable, generic, fast and flexible logging framework.
* Copyright (C) 1999-2009, QOS.ch. All rights reserved.
*
* This program and the accompanying materials are dual-licensed under
* either the terms of the Eclipse Public License v1.0 as published by
* the Eclipse Foundation
*
* or (per the licensee's choosing)
*
* under the terms of the GNU Lesser General Public License version 2.1
* as published by the Free Software Foundation.
*/
package ch.qos.logback.classic.pattern;
import ch.qos.logback.classic.spi.ILoggingEvent;
import ch.qos.logback.core.pattern.Converter;
import ch.qos.logback.core.pattern.ConverterUtil;
import ch.qos.logback.core.pattern.PostCompileProcessor;
public class EnsureExceptionHandling implements
PostCompileProcessor<ILoggingEvent> {
/**
* This implementation checks if any of the converters in the chain handles
* exceptions. If not, then this method adds a
* {@link ExtendedThrowableProxyConverter} instance to the end of the chain.
* <p>
* This allows appenders using this layout to output exception information
* event if the user forgets to add %ex to the pattern. Note that the
* appenders defined in the Core package are not aware of exceptions nor
* LoggingEvents.
* <p>
* If for some reason the user wishes to NOT print exceptions, then she can
* add %nopex to the pattern.
*
*
*/
public void process(Converter<ILoggingEvent> head) {
if (!chainHandlesThrowable(head)) {
Converter<ILoggingEvent> tail = ConverterUtil.findTail(head);
Converter<ILoggingEvent> exConverter = new ExtendedThrowableProxyConverter();
if (tail == null) {
head = exConverter;
} else {
tail.setNext(exConverter);
}
}
}
/**
* This method computes whether a chain of converters handles exceptions or
* not.
*
* @param head
* The first element of the chain
* @return true if can handle throwables contained in logging events
*/
public boolean chainHandlesThrowable(Converter head) {
Converter c = head;
while (c != null) {
if (c instanceof ThrowableHandlingConverter) {
return true;
}
c = c.getNext();
}
return false;
}
}