Does scala have that many third party libraries ala java ? Because these days for web application most of us use Java with Spring or apache commons.
This is not entirely dissimilar from the way that JSP gets converted into a Servlet.
Scala/AlternateLanguageRunningOnJVM fans please provide corrections as appropriate, but be gentle, I'm making some broad generalisations here with all the flaws implied by that methodology. :D
Another issue is using scala code from java. As long as the code implements a plain java interface, everything is fine, but if you try to use something impemented with some of the features that java doesn't have, you will soon see some very stange mangled names. trö_%¿ is not a valid java fuction name, after all.
You can easily use any Java libraries from Scala and Scala provides a number of tools including JavaConversions and JavaConverters to automatically convert to and from Scala and Java collection objects for easy interop.