I'm not big on making predictions, but this one seems pretty obvious to me. The reason there are so many Java web frameworks is that they all suck at being web frameworks. There is no clear winner in the Java space. We started with Servlets, which were terrible for web development because you couldn't tell what the heck the final HTML would look like. Then we had JSP, which is better, but once you start trying to apply DRY, get into a templating system and tag libraries, you're suddenly just as removed from the final result as you were with Servlets. In both cases, if I want to know what is being produced, I have to fire up my JEE container and do a request. Not to mention that creating templates and tags requires some lovely combination of XML and Java code. I don't know about you, but that feels off to me.
Why? XML doesn't give me much flexibility. DRY gets violated all the time because there is no mechanism in the design of XML for reasonable reuse. Java on the other hand lets me refactor and reuse to my heart's content, but as we've already established, it's crap for actually producing HTML.
And what about Ajax? JSP is fine if your site uses tables for layout and all links result in a full page refresh or occasional popup window, but if you want to build a responsive, dynamic site (using say, Ext) you'll end up having rendering logic in two places, WhateverCrapFramework and JavaScript. The best possible outcome is that you hardly use JSP (or whatever your 'controller' is) and rely on your Ajax toolkits.
Again why? Because static typing everything is not appropriate for user interfaces. A user only has one input type available to them: text. They can't enter
FooBarDtos directly, they don't even know what one is. You have to take some text and convert and validate it. Granted, they can also click things, but HTTP seals the deal for the web because all data submitted must be in text form. Your types cannot help you until you have already converted and validated the data, at which point it's ready to pass on to your service layer. So why the heck do you need types everywhere in your controller? You don't, but Java forces them on you anyways.I think Java is great for web applications by the way. Spring+Hibernate remains my first choice for implementing a solid service and data access layer (I like Guice too). Static typing is great for helping ensure that your services are solid, and your data remains valid.
Back to Ajax. I made a big investment in JSF in graduate school. I nearly killed myself and my wife building a framework for creating Ajax enabled components for JSF. It took me a few months after finishing to realize that JSF still doesn't make Java web development any less like wearing plate mail while figure skating.
When you get right down to it, the best language for developing a web UI is the language that was always meant for the web: JavaScript. DWR completely bridges the gap between Java and JavaScript. It converts all that pesky string data into nice typed data for your Java service layer and then turns around and converts those types that the user doesn't know about into pleasant little strings for web browsers to gobble up. You can expose your Spring service beans directly, secure them with Acegi (you better be doing that anyway, if you're relying on your controller to secure access, you're using a sieve as an umbrella), and call them from JavaScript without even having to know how HTTP requests work, much less Ajax.
In conclusion, we need real developers on the client side. Good designers/UX folk don't usually make the best technical developers, and the dynamic web (especially for enterprise) requires a solid, coherent client side codebase, and things like DWR make that easy. If you're a Java web application developer that's still afraid of JavaScript, you'd better learn to face your fears.
