Web File Extensions are Bad

I hate file extensions on websites.  It is an unnecessary leaky abstraction, and is discouraged by the W3C.  All file extensions are not necessarily bad, but any file extension that exposes the underlying technology implementation is.  Any .pl, .php, .asp, .aspx, .jsp, .do, *.struts, etc extensions are B A D.

I've talked about this before, and come up with some workarounds to build extension-less java web applications before.

However, I've come across what I think is a better way, thanks to a post a couple years ago by Matt Raible.

I came across the issue using the Spring WebMVC DispatcherServlet.  I want all dynamic URLs handled by the Spring Controllers, using Annotations.  However, mapping the DispatcherServlet to /* means that every URL will be processed by the DispatcherServlet, including the .jsp views returned by the Controller.  As I mentioned in the previous post, you can 'unmap' content and have it handled by a default or jsp servlet in some app servers, but not all.

You can also try to map specific subsets of URLs to spring.  However, this is harder than it sounds.  By default, Spring will map the wildcard portion of the URL matched, not the entire URL.  So if you have /foo/* as your url-pattern, the controller with a mapping of /foo/one will not match /foo/one, but instead matches /foo/foo/one.

It appears that you can use the property alwaysUseFullPath to change this behavior, but it did not seem to work as expected for me.

Instead, there is a more generalized solution, as Matt suggested.  URL Rewriting.

The URL Rewrite Filter project provides a Filter that you easily define rewrite rules for, just like in Apache.  So I setup my DispatcherServlet to match *.spring, I setup a rule to rewrite all extension-less requests to .spring, and I setup my annotations to have the .spring extension.

Now my web application can handle the odd html, png, or other static files if necessary, but does not expose any implementation details in the URLs.  Perfect.

For reference, here are the relevant portions of my config:

Web.xml

<?xml version="1.0" encoding="UTF-8"?>
<web-app version="2.5" xmlns="http://java.sun.com/xml/ns/javaee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd">

  <filter>
    <filter-name>UrlRewriteFilter</filter-name>
    <filter-class>org.tuckey.web.filters.urlrewrite.UrlRewriteFilter</filter-class>
  </filter>
  
  <filter-mapping>
    <filter-name>UrlRewriteFilter</filter-name>
    <url-pattern>/*</url-pattern>
  </filter-mapping>
  
  <servlet>
    <servlet-name>SpringMVCServlet</servlet-name>
    <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
      <init-param>
        <param-name>contextConfigLocation</param-name>
        <param-value>/WEB-INF/your.config.file.location.xml</param-value>
      </init-param>
    <load-on-startup>1</load-on-startup>
  </servlet>
  
  <servlet-mapping>
    <servlet-name>SpringMVCServlet</servlet-name>
    <url-pattern>*.spring</url-pattern>
  </servlet-mapping>
  
</web-app>

urlrewrite.xml

<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE urlrewrite PUBLIC "-//tuckey.org//DTD UrlRewrite 3.0//EN"
  "http://tuckey.org/res/dtds/urlrewrite3.0.dtd">

<urlrewrite>
  <rule>
    <from>/$</from>
    <to type="forward">home</to>
  </rule>

  <rule>
    <from>^([^?]*)/([^?/\.]+)(\?.*)?$</from>
    <to last="true">$1/$2.spring$3</to>
  </rule>
  
</urlrewrite>

Sample Controller

@Controller
@RequestMapping("/foo")
public class SimpleDataController {

  @RequestMapping("/bar.spring")
  public ModelAndView bar() {
    ...
  }
}