2. JNI debug is a bit of pain probably. But Java/Groovy/etc much easier to debug, compared to, say, Python
3. IMO there're no much reason to use pure Java in webdev. Only if you have well defined project, maybe already written in JVM language, that you want to optimize
4. Depends on language. Clojure have one. Groovy/Grails too.
I was never managed to debug python code :( Maybe i'm doing something wrong. Never mind, I didn't want to offend python, it's only language I like besides jvm languages.
On other hand on JVM you don't even need such line, all works out of box, w/o code modification, never had any problem. At least with java and groovy
2. stacktraces != debug. I don't actually see any difference with java stacktrace (only that it contains groovy classes, but it's still exactly same format). I mean tools for debug, like debug in IDE (look at Intellij IDEA, very powerful in debug), or JMX, take a look at VisualVM and profiling tools. There're many different tools. It's not just stacktrace.
5. Agree, not so popular that plain Spring maybe. But still, we're talking about features, right? not amount of projects on prod. Grails is pretty comparable to Rails/Django, in terms of features. Also, version 3 is too new, it requires to rewrite a lot of stuff to migrate. It takes time.
3. IMO there're no much reason to use pure Java in webdev. Only if you have well defined project, maybe already written in JVM language, that you want to optimize
4. Depends on language. Clojure have one. Groovy/Grails too.
5. check Grails