Simple RESTful URLs with JSPs

Bill de hOra posted an interesting question the other day, that has to do with mapping views to requests, cleanly, in a RESTful way, as Sam Ruby framed it:

it’s easy to forget that Servlets were Java’s response to CGI, way back when. Here’s is the link for Stefan’s entry:

I’m wondering how would one produce a URL space for a blog style archive, using Servlets+JSP, and do so in a way that isn’t a CGI/RPC explicit call? That is, the URLs don’t end up like this:

with one constraint – “just a servlet” that pulls java_web_frameworks.html direct from a “2007/08/15” folder on the filesystem and byapsses JSP is out. All the response is to be generated via JSP. Would we need to a create framework, however ‘micro’?

In Django world, answering such a question is rather easy. And for PHP hackers, you’re probably saying, hey, use .htaccess to route requests, but in Java, this question becomes a bit more complicated.

A Java developer would want solve two problems here: enable “clean” RESTful URLs, and do as little Java coding as possible by distributing responsibility for defining views to a templating language. Hopefully empowering someone who knows just HTML/CSS to work their magic. The benefits to such an approach can’t be underestimated. We we went down such a path at Knight Ridder with the Cofax CMS and it empowered a lot of creativity with little resources on hand (lots of folks know HTML/CSS/JS, few know Java).

Carbon Five discusses an approach that decomposes path info into parameters for Spring MVC controllers: Parameterized REST URLs with Spring MVC. This solves problem one. It still routes requests to a Controller defined in Java, and I’ve seen far too many not solve problem two, which leaves a design where you have a Request, that maps to a Controller that maps to a single View. But this leaves you with an *excellent* foundation to solve the second problem.

Sam Ruby points to URLRewriteFilter as one possible solution. This potentially solves both problems.

Stefan Tilkov explains how to decompose path info and use RequestDispatcher as a solution. In Sam Ruby’s comments, I suggested just such an approach and it’s worked great for me in previous (and current) projects. This potentially solves both problems.

BTW, if you’re interested in a templating language, outside of JSP (and who isn’t?), consider FreeMarker. A huge project I’m helping design and develop is having terrific success with it and Spring MVC. Real magic starts to happen when you decouple Requests from Views. A shortcut to this in Spring MVC is implementing a RequestToViewNameTranslator.