package loggerbug;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

public class Loggerbug
{
private static final Logger logger = LoggerFactory.getLogger(Loggerbug.class);

static class ThrowsToString {
@Override
public String toString()

{ throw new RuntimeException("from toString"); }

}

public static void main(String[] args)
{
ThrowsToString probe = new ThrowsToString();
logger.info("probe is {}", probe);
System.out.println("no exception");
}
}

prints "no exception" with logback-classic, but with slf4j-simple output is:

Exception in thread "main" java.lang.RuntimeException: from toString
at loggerbug.Loggerbug$ThrowsToString.toString(Loggerbug.java:13)
at java.lang.String.valueOf(String.java:2827)
at java.lang.StringBuffer.append(StringBuffer.java:219)
at org.slf4j.helpers.MessageFormatter.deeplyAppendParameter(MessageFormatter.java:237)
at org.slf4j.helpers.MessageFormatter.arrayFormat(MessageFormatter.java:196)
at org.slf4j.helpers.MessageFormatter.format(MessageFormatter.java:138)
at org.slf4j.impl.SimpleLogger.formatAndLog(SimpleLogger.java:222)
at org.slf4j.impl.SimpleLogger.info(SimpleLogger.java:258)
at loggerbug.Loggerbug.main(Loggerbug.java:20)