You could easyly write your own discriminator class combining
JNDIBasedContextDiscriminator and MDCBasedDiscriminator. Here is an example:

public class CombinedDiscriminator extends ContextAwareBase implements
Discriminator<ILoggingEvent> {

private String defaultMDCVal = "default";

public String getDiscriminatingValue(ILoggingEvent event) {
String mdcValue = defaultMDCVal;
Map<String, String> mdcMap = event.getMdc();
if (mdcMap != null) {
mdcValue = mdcMap.get(key);
}
String contextName = event.getLoggerContextVO().getName();
return contextName + mdcValue;
}
..etc
}

Thanks for reply, i started to implement, but i noticed that maybe i don't explain well, i dont need "sumValue = contextName + mdcValue" value to use in <FileNamePattern>${newValue}.log</FileNamePattern>

That i really need is two values... contextName and mdcValue...

The aprox, maybe something like <FileNamePattern>${newValue.substring(0,x)}/${newValue.substring(x,n)}.log</FileNamePattern>

or something like

<appender ... class="ch.qos.logback.classic.sift.SiftingAppender">
    <discriminator class="ch.qos.logback.classic.sift.JNDIBasedContextDiscriminator">
    ...
        <sift>
            <appender ... class="ch.qos.logback.classic.sift.SiftingAppender">
                <discriminator>
                ...
                <sift>
                    <appender class="ch.qos.logback.core.rolling.RollingFileAppender">