This weekend I decided to give Leopard a shot and so far, so good. However, if you’re an Eclipse fan you will be disappointed. I should also add folks who use ANY Eclipse-based product including Flex Builder 3 Beta 2 and apparently Zend Neon as well, according to the commenter’s over at The Job of Flex blog. The long of the short is that anytime you try and use the Open Resource dialog and make your selection an hit “Ok”, Eclipse will crash.

Since Eclipse uses it’s own SWT, it’s hard to say if this is an Apple issue or an Eclipse issue. Seeing as how, Swing applications seem to be much more stable and perform better, I’m thinking this is an Eclipse bug. Even though Mac OS X is still a minority platform for the Eclipse group, it’s issues like this back up my prior assertion regarding SWT vs. Swing. But with all of that said, I have filed 2 bugs: one for the Eclipse IDE here and another for Flex Builder here. If you’re having the same issues I am experiencing, please vote for these bugs. In the meantime, I’m giving the latest Netbeans RC 2 a good hard look. So far, I’m very impressed with how it runs under Leopard.

Thanks to several commenter’s who pointed out several issues with in my URI vs. URL post, I have made several revisions that post to be more correct. If you happen to be linking to that post, or citing comments from it in a post of your own, you may want update it.

Updated (8/27/2009): I’ve created another post that attempts to make the distinctions a bit more clear. The new post is here.

What is the difference between a URL and URI and why does it matter? This topic is confusing to some (myself included) and I thought I’d share my understanding of the two concepts. I’m hoping this post will give you a better understanding about how the two differ and why it matters to some.

Note: The goal of this post is to simplify the distinction between URI and URI. If you feel that in the summarization process something was lost, or it’s simply just correct, please post a comment and the information will be corrected. I only ask for any comments/criticism to be constructive.

Update: Thanks some constructive, and not-so constructive, feedback from some readers I have updated this post to correct many of my own misunderstandings. Of which, there were many.

URI

A URI identifies a resource either by location, or a name, or both. More often than not, most of us use URIs that defines a location to a resource. The fact that a URI can identify a resources by both name and location has lead to a lot of the confusion in my opionion. A URI has two specializations known as URL and URN.

URN

A URI identifies a resource by name in a given namespace but not define how the resource maybe obtained. This type of URI is called a URN. You may see URNs used in XML Schema documents to define a namespace, usually using a syntax such as:

<xsd:schema xmlns="http://www.w3.org/2001/XMLSchema"
            xmlns:xsd="http://www.w3.org/2001/XMLSchema"
            targetNamespace="urn:example"

Here the targetNamespace use a URN. It defines an identifier to the namespace, but it does not define a location.

URL

A URL is a specialization of URI that defines the network location of a specific resource. Unlike a URN, the URL defines how the resource can be obtained. We use URLs every day in the form of http://damnhandy.com, etc. But a URL doesn’t have to be an HTTP URL, it can be ftp://damnhandy.com, smb://damnhandy.com, etc.

The Difference Between Them

So what is the difference between URI and URL? It’s not as clear cut as I would like, but here’s my stab at it:

A URI is an identifier for some resource, but a URL gives you specific information as to obtain that resource. A URI is a URL and as one commenter pointed out, it is now considered incorrect to use URL when describing applications. Generally, if the URL describes both the location and name of a resource, the term to use is URI. Since this is generally the case most of us encounter everyday, URI is the correct term.

For the misinformed, there is no re-release of of the Java 6 preview on the ADC site. This “preview release 6″ merely updates Java 5. 1.5.0_13 and Java 1.4 to 1.4.2_16. Basically, it brings Java in Tiger up to he same versions that is in Leopard.

I just came across a quick article on The Server Side about a JSF framework called RESTFaces. My initial reaction was “oh cool, a JSF framework that might adhere to RESTful principals.” Sadly, there isn’t much more than HTTP GET support that is “RESTful” about RESTFaces. RESTFaces touts itself as being a

RESTfaces for JavaServer™ Faces Technology make it possible to write bookmarkable pages using JavaServer™ Faces.

In a nut shell: RESTFaces allows you to invoke actions via HTTP GET as opposed to just POST actions. JBoss Seam has a similar feature and their docs describes it as a means of making RESTFul applications that can be bookmarked. To be fair, Seam does not claim to be a full-on REST framework. Now I am a huge fan of JBoss Seam, so I don’t mean to come off as pooh-poohing that effort. But I wonder, is just providing GET support enough enough to be considered RESTful? At a low level, probably yes. But there could be so much more.

This could all change as the specifications for JSF and Web Beans matures. JSR-311 is a thriving work in progress and JSR-314 is also still getting ramped up as well. As these spec mature, some nice integration points might be:

Support for URI templates.

JSR-311 is currently defining support for this, but if this were integrated into JSF URIs would not be just bookmarkable, but also human readable. For example, instead of:

http://somehost/blog/entry.action?id=1234

You could have something a bit cleaner

http://somehost/blog/entries/1234

Your entry ID is now a component of the URI, which makes it a lot easier on the eyes. If you ever have had to deal with marketing applications, you can appreciate the value of this.

Support for multiple representations via HTTP Content Negotiation

Again this is something that JSR-311 is defining, but if this is integrated into JSF, or Web Beans for that matter, it would allow a single URI to deliver different media types. Using the example above, the same URI:

http://somehost/blog/entries/1234

Could deliver the content as a PDF, or an HTML format that is more suitable for a mobile device and the decision is made by the framework. The user would not have to execute a specific URL for each type:

http://somehost/blog/entries/1234.html

http://somehost/blog/entries/1234.pdf

http://somehost/blog/entries/1234.wml

Or worse:

http://somehost/blog/entry.action?id=1234&type=application/pdf

http://somehost/blog/entry.action?id=1234&type=text/html

Through content negotiation, the user just needs the URI and the application will take care of delivering the proper response. If you’re looking for an example of a present day implementation, look no further than Apache HTTPD. JBoss Seam already supports a number of ways to generate other media types such as PDF, charts and graphs, and other, so I think they’re in a great position to deliver this kind of functionality. On the plus side, at least these two frameworks do allow one to use HTTP GET which is a big help.