With all of the buzz about the Play vs Grails Smackdown
at Devoxx last week, and this framework benchmark comparison from TechEmpower, I thought it would be interesting to look again at Rossen Stoyanchev’s demo project that integrates Spring MVC with Netty. He had mentioned it on the SpringSource internal developer list and I bookmarked it for later since I was curious about Netty.
I spent the weekend converting Rossen’s code to work with Grails, and created a plugin, borrowing some code from the Spring mock Servlet API classes and also from Tomcat. It’s a weird plugin in that it runs concurrently with the regular web app on a different port. I’m currently taking advantage of the work that Grails does, e.g. creating the Spring ApplicationContext, compiling GSPs in production WARs, etc. But it should be easy enough to get it to run standalone. It’s similar to the Dropwizard plugin, which also adds an alternative and higher-performance request path within a Grails application.
Netty is a generic (but high-performance) network library, so it doesn’t have extensive support for the Servlet API. But it does support HTTP, and that’s what Rossen’s code and my version add – a bridging layer between the lower-level Netty approach and the Servlet API. Ideally this provides a performance and scalability boost from Netty’s non-blocking IO, with the familiarity of the request/response/session approach in the Servlet API.
Most everything works in the plugin, but there are some omissions. There’s no support for SSL, and file upload isn’t implemented. You can do all of the usual Grails stuff, i.e. use controllers, services, GORM, etc. There is support for HTTP Sessions, although they’re not serialized to disk at shutdown and there’s no support for distributed sessions. But other than these items, making requests on the Netty port should work pretty much the same as requests on the servlet container port.
You can install the plugin in the usual way, i.e. add this to BuildConfig.groovy
compile ':nettymvc:0.1'
It will start a server socket on port 8080 by default, but you can configure that in Config.groovy, e.g.
grails.plugin.nettymvc.port = 8090
The plugin page is here and the source is here. Please try it out and let me know if there are issues or if you have suggestions for improvements, ideally in the form of pull requests of course 
