Raible Designs

Implementing Extensionless URLs with Tapestry, Spring MVC, Struts 2 and JSF

For the past couple of weeks, I've spent several evening hours implementing extensionless URLs in AppFuse. I've been wanting to do this ever since I wrote about how to do it a few years ago. This article details my experience and will hopefully help others implement this feature in their webapps.

First of all, I used the UrlRewriteFilter, one of my favorite Java open source projects. Then I followed a pattern I found in Spring's "mvc-basic" sample app from MVC Simplifications in Spring 3.0. The app has since changed (because SpringSource integrated UrlRewriteFilter-type functionality in Spring MVC), but the pattern was basically path-matching instead of extension-mapping. That is, the "dispatcher" for the web framework was mapped to /app/* instead of *.html.

Prior to the move to extensionless URLs, AppFuse used *.html for its mapping and this seemed to cause users problems when they wanted to serve up static HTML files. To begin with, I removed all extensions from URLs in tests (Canoo WebTest is used for testing the UI). I also did this for any links in the view pages and redirects in the Java code. This provided a decent foundation to verify my changes worked. Below are details about each framework I did this for, starting with the one that was easiest and moving to hardest.

Tapestry 5
Tapestry was by far the easiest to integrate extensionless URLs into. This is because it's a native feature of the framework and was already integrated as part of Serge Eby's Tapestry 5 implementation. In the end, the only things I had to do where 1) add a couple entries for CXF (mapped to /services/*) and DWR (/dwr/*) to my urlrewrite.xml and 2) change the UrlRewriteFilter so it was only mapped to REQUEST instead of both REQUEST and FORWARD. Below are the mappings I added for CXF and DWR.

<urlrewrite default-match-type="wildcard">
    ...
    <rule>
        <from>/dwr/**</from>
        <to>/dwr/$1</to>
    </rule>
    <rule>
        <from>/services/**</from>
        <to>/services/$1</to>
    </rule>
</urlrewrite>

Spring MVC
I had a fair amount of experience with Spring MVC and extensionless URLs. Both the Spring MVC applications we developed last year at Time Warner Cable used them. To change from a *.html mapping to /app/* was pretty easy and involved removing more code than I added. Previously, I had a StaticFilter that looked for HTML files and if it didn't find them, it dispatched to Spring's DispatcherServlet. I was able to remove this class and make the web.xml file quite a bit cleaner.

To make UrlRewriteFilter and Spring Security play well together, I had to move the securityFilter so it came after the rewriteFilter and add an INCLUDE dispatcher so included JSPs would have a security context available to them.

<filter-mapping>
    <filter-name>rewriteFilter</filter-name>
    <url-pattern>/*</url-pattern>
</filter-mapping>
<filter-mapping>
    <filter-name>securityFilter</filter-name>
    <url-pattern>/*</url-pattern>
    <dispatcher>REQUEST</dispatcher>
    <dispatcher>FORWARD</dispatcher>
    <dispatcher>INCLUDE</dispatcher>
</filter-mapping>

The only other things I had to change were security.xml and dispatcher-servlet.xml to remove the .html extensions. The urlrewrite.xml file was fairly straightforward. I used the following at the bottom as a catch-all for dispatching to Spring MVC.

<rule>
    <from>/**</from>
    <to>/app/$1</to>
</rule>
<outbound-rule>
    <from>/app/**</from>
    <to>/$1</to>
</outbound-rule>

Then I added a number of other rules for j_security_check, DWR, CXF and static assets (/images, /scripts, /styles, /favicon.ico). You can view the current urlrewrite.xml in FishEye. The only major issue I ran into was that Spring Security recorded protected URLs as /app/URL so I had to add a rule to redirect when this happened after logging in.

<rule>
    <from>/app/**</from>
    <to last="true" type="redirect">%{context-path}/$1</to>
</rule>

Struts 2
Using extensionless URLs with Struts 2 is likely pretty easy thanks to the Convention Plugin. Even though this plugin is included in AppFuse, it's not configured with the proper constants and I have struts.convention.action.disableScanning=true in struts.xml. It looks like I had to do this when I upgraded from Struts 2.0.x to Struts 2.1.6. It's true AppFuse's Struts 2 support could use a bit of love to be aligned with Struts 2's recommended practices, but I didn't want to spend the time doing it as part of this exercise.

With Struts 2, I tried the path-mapping like I did with Spring MVC, but ran into issues. Instead, I opted to use an ".action" extension by changing struts.action.extension from "html" to "action," in struts.xml. Then I had to do a bunch of filter re-ordering and dispatcher changes. Before, with a .html extension, I had all filters mapped to /* and in the following order.

Similar to Spring MVC, I had to remove the rewriteFilter in front of the securityFilter and I was able to remove the staticFilter. I also had to map the struts filter to *.action instead of /* to stop Struts from trying to catch static asset and DWR/CXF requests. Below is the order of filters and their dispatchers that seems to work best.

From there, it was a matter of modifying urlrewrite.xml to have the following catch-all and rules for static assets, j_security_check and DWR/CXF.

<rule match-type="regex">
    <from>^([^?]*)/([^?/\.]+)(\?.*)?$</from>
    <to last="true">$1/$2.action$3</to>
</rule>
<outbound-rule match-type="regex">
    <from>^(.*)\.action(\?.*)?$</from>
    <to last="false">$1$2</to>
</outbound-rule>

JSF
JSF was by far the most difficult to get extensionless URLs working with. I'm not convinced it's impossible, but I spent a several hours over a few days and was unsuccessful in completely removing them. I was able to make things work so I could request pages without an extension, but found when clicking buttons and links, the extension would often show up in the URL. I'm also still using JSF 1.2, so it's possible that upgrading to 2.0 would solve many of the issues I encountered.

For the time being, I've changed my FacesServlet mapping from *.html to *.jsf. As with Struts, I had issues when I tried to map it to /app/*. Other changes include changing the order of dispatchers and filters, the good ol' catch-all in urlrewrite.xml and modifying security.xml. For some reason, I wasn't able to get file upload working without adding an exception to the outbound-rule.

<rule match-type="regex">
    <from>^([^?]*)/([^?/\.]+)(\?.*)?$</from>
    <to last="true">$1/$2.jsf</to>
</rule>
<outbound-rule match-type="regex">
  <!-- TODO: Figure out how to make file upload work w/o using *.jsf -->
    <condition type="path-info">selectFile</condition>
    <from>^(.*)\.jsf(\?.*)?$</from>
    <to last="false">$1$2</to>
</outbound-rule>

I also spent a couple hours trying to get Pretty Faces to work. I wrote about my issues on the forums. I tried writing a custom Processor to strip the extension, but found that I'd get into an infinite loop where the processor kept getting called. To workaround this, I tried using Spring's RequestContextHolder to ensure the processor only got invoked once, but that proved fruitless. Finally, I tried inbound and outbound custom processors, but failed to get those working. The final thing I tried was url-mappings for each page in pretty-config.xml.

<url-mapping>
  <pattern value="/admin/users"/>
  <view-id value="/admin/users.jsf"/>
</url-mapping>
<url-mapping>
  <pattern value="/mainMenu"/>
  <view-id value="/mainMenu.jsf"/>
</url-mapping>

The issue with doing this was that some of the navigation rules in my faces-config.xml stopped working. I didn't spend much time trying to diagnose the problem because I didn't like having to add an entry for each page in the application. The one nice thing about Pretty Faces is it did allow me to do things like the following, which I formerly did with a form that auto-submitted when the page loaded.

<url-mapping>
  <pattern value="/passwordHint/#{username}"/>
  <view-id value="/passwordHint.jsf"/>
  <action>#{passwordHint.execute}</action>
</url-mapping>

Conclusion
My journey implementing extensionless URLs was an interesting one, and I solidified my knowledge about ordering of filters, dispatchers and the UrlRewriteFilter. I still think I have more to learn about properly implementing extensionless URLs in Struts 2 and JSF and I hope to do that in the near future. I believe Struts' Convention Plugin will help me and JSF 2 + Pretty Faces will hopefully work nicely too. Of course, it'd be great if all Java Web Frameworks had an easy mechanism for producing and consuming extensionless URLs. In the meantime, thank goodness for the UrlRewriteFilter.

If you'd like to try AppFuse and its shiny new URLs, see the QuickStart Guide and choose the 2.1.0-SNAPSHOT version.