Raible Designs

[CSS] Mule - A Detailed Look at an Enterprise Service Bus by Tom Bender

Below are notes I took while attending Tom Bender's talk on Mule at the Colorado Software Summit:

SOA: A collection of services with well-defined interfaces and a shared communication model is called a service-oriented architecture.

ESB: Provides a light weight, loosely coupled, event-driven SAO with a highly distributed universe of naming routing destinations across a multi-protocol message bus.

Four Tenets of SAO (as proposed by Don Box):

• Boundaries are Explicit
• Services are Autonomous
• Services share Schema and Contract, not Class
• Compatibility is based upon Policy

Properties of an ESB: Light Weight, Loosely Coupled, Event-Driven, Transactional, Securable, Distributed Network Topologies, Abstract Endpoints, Intelligent Routing, Message Transformation (inbound/outbound), Multi-Protocol Message Bus.

One of the main differences between application servers and ESBs is appservers are traditionally integrated with a hub-and-spoke architecture. ESBs, on the other hand, use a distributed integration architecture.

Mule - What is it?

Ross Mason is the founder and primary developer of Mule. From its homepage:

Mule is an Enterprise Service Bus (ESB) messaging framework. It is a scalable, highly distributable object broker that can seamlessly handle interactions with services and applications using disparate transport and messaging technologies.

Mule is an event-based architecture. Actions within a Mule network are triggered by either events occurring in Mule or in external systems. It's a light-weight messaging framework that's highly distributable and very pluggable (i.e. for multiple transports and protocols). Mule supports Web Services using Axis or Glue.

A Closer Look at Mule

The basic building block is a "UMO Component". This component is used to wire applications together - it's basically a POJO that can optionally implement interfaces if it wants to hook into lifecycle events. An application communicates with the UMO component through a channel (i.e. TCP/IP or JMS). This channel talks to a message receiver that works with a connector that's backed by a transformer and formats it for the UMO component (whoa, that's a mouthful - and that's only inbound!). When going to the receiving application, the process starts from the UMO component, goes though the outbound router - and plows through the whole transformer » connector » message dispatch » channel » application process again. Here's a diagram of this process that I found on Mule's website:

Mule supports many different endpoints: POP3/SMTP, JMS Topic or Queue, HTTP, File, VM (w/in the JVM), SOAP, RMI and EJB. Each of these have their own URI prefix.

I tuned out for the rest of Tom's talk (sorry Tom). The whole ESB topic is pretty dry IMO, but Tom seemed to do a good job of keeping the audience interested.

What's a good DVI KVM?

I'm looking to get a KVM Switch for my home office. I used to have one when I had 2 19" Dell Monitors and it worked quite well. However, since I got a 23" Cinema Display, I haven't had one. This means that if I ever work on my PowerBook, I don't get to enjoy the comfort of a keyboard, mouse and huge monitor. This needs to change.

I bought a DVI KVM switch when I first got the monitor a year ago, and it didn't work. Apple's DVI connector was too big and didn't fit in the switch. So now I'm looking again - do you know of any that work well with a Cinema Display?

What's the best way to integrate Ajax into a Java webapp?

I received an e-mail over the weekend asking how to integrating Ajax into into the various web frameworks covered in my Java Web Framework Comparison Whitepaper. Below is my reply:

The best thing that I've seen is to use DWR, Prototype and Scriptaculous.
These will work with all web frameworks, and if you're using Spring on the backend -
DWR makes it easy to expose your beans as JavaScript objects.

Also, there's a number of tag library solutions that greatly simplify things:

  http://javawebparts.sf.net
  http://ajaxanywhere.sf.net
  http://ajaxtags.sf.net

I haven't used the first one, but I have used AjaxAnywhere and saw a demo of
AjaxTags from its developers.  They both look like they could be very useful.

For those of you using Ajax in your Java webapps - what's your advice? Do you use these same libraries or other ones?

This post was partially motivated by my desire to reiterate things that are so obvious.

Roller gets some respect

From A Baggins Under the Hill (nice looking theme BTW):

There's a surprising (or perhaps not so surprising) number of PHP programs, intricate ones at that, that have developers who didn't bother to abstract away the database layer, and wrote DB-vendor-dependent queries. That's a pretty horrible thing to do, since it ties you quite firmly down to one DB (in many cases MySQL). The SQL code is often very tightly integrate with the display code; it's bad enough in the business layer, but the view layer as well? Good gods.
...
Roller, on the other hand, uses things like Hibernate to abstract away queries from the underlying DB implementations, and Velocity to separate out the display logic from the business logic. And blogging software does have business logic, or a model; blog entries and categories and tags and authentication and the manipulation thereof are not simple. As a result, I see features being added to Roller that I'm surprised to see happening so quickly.

As far as solving the issue with Tomcat 5.5, that's just a matter of updating your $CATALINA_HOME/conf/Catalina/localhost/roller.xml file. Here's what I use for Roller on PostgreSQL:

<Context path="/roller" docBase="roller" debug="99" reloadable="false"
    antiJARLocking="true" antiResourceLocking="false">

    <Realm className="org.apache.catalina.realm.JDBCRealm" debug="99"
          driverName="org.postgresql.Driver"
       connectionURL="jdbc:postgresql://localhost/roller"
      connectionName="postgres" connectionPassword="postgres"
           userTable="rolleruser" userNameCol="username" userCredCol="passphrase"
       userRoleTable="userrole" roleNameCol="rolename" />

    <Resource name="jdbc/rollerdb" auth="Container" type="javax.sql.DataSource"
              maxActive="20" maxIdle="10" maxWait="100"
              driverClassName="org.postgresql.Driver"
              username="postgres" password="postgres"
              url="jdbc:postgresql://localhost/roller"/>

    <Resource name="mail/Session" auth="Container" type="javax.mail.Session"
              mail.smtp.host="localhost" />
</Context>

Maven 2's Transitive Dependencies

I spent a few hours this week integrating Maven 2's Ant tasks into Equinox. Here's a things I discovered in the process.

• The JAR you need to include to use the Maven Tasks is quite large, weighing in at a hefty 833K. Regardless, it's easier to include a ~1MB JAR in CVS than it is 10MB of JARs. Equinox (w/o the extras directory) weighs in at 10.2MB before, 1.3MB after.
• The transitive dependencies feature needs to be cleaned up a fair bit. There are a *lot* of unnecessary dependencies downloaded for many libraries. For example, Hibernate downloads a bunch of JBoss JARs and the Display Tag downloads all the various web framework JARs. I found myself excluding almost as many dependencies as I added.
• Using in-line dependencies (where you specify each one in your build.xml) is cleaner and requires less XML (b/c of attributes vs. elements). I went this route at first and it worked well, but to allow greater flexibility (for those who might want to use Maven 2), I ended up creating a pom.xml. 48 lines in build.xml turned into 195 lines in pom.xml.
• The Maven Developer team provides fantastic support - both on the mailing list and IRC. Thanks Brett!
• Maven 2.0 RC was released today.
• I need to figure out a way to "install" the persistence/web framework options in Equinox. The easiest way from a maintenance perspective is to parse pom.xml to add new dependencies. Entity includes might make the project more extensible though - and easier to upgrade.
• Once you have pom.xml in place, it's pretty easy to make the build/test/package process M2 friendly.
• Maven 2 is faster than Ant.

Overall, it was a pretty frustrating experience, with lots of trail-and-error. In the end, I got it all figured out and the only "hack" I had to do was delete servlet-api-2.4.jar after copying dependencies into my WAR. This is b/c Ant is not smart enough to know that dependencies with a "provided" scope shouldn't be copied. I could probably have a 4th dependencies path to solve this, but deleting sounded easier at the time.

I'm not going to check anything in yet b/c I still have to modify all the installers to specify their dependencies. The main advantage I can see in using a download-dependencies feature is easier upgrading of dependencies. It'll also make a lot more sense in AppFuse b/c certain parts of project (i.e. appfuse-dao.jar) can be published as re-usable modules.

In the meantime, if you'd like to try out Equinox with this feature (works with both Maven 2 or Ant), you can integrate it into a CVS version with the following steps:

• In the equinox directory, create a lib directory and download maven-artifact-ant-2.0-dep.jar into it.
• Replace your build.xml with this build.xml (view diff against current).
• Download pom.xml and put it in the equinox directory.
• Delete web/WEB-INF/lib.

That's it! I'm sure some things can be improved - please let me know if you find any issues.

DWR and Script.aculo.us now included in AppFuse and Equinox

Last night, I integrated DWR into both AppFuse and Equinox. AppFuse has had Script.aculo.us integrated since 1.8.2 and it's been great to work with - so I added it to Equinox as well. I added these with the philosophy that it's easier to remove them than to add them.

Thanks to Joe Walker (DWR), Thomas Fuchs (Script.aculo.us) and Sam Stephenson (Prototype) for authoring (and supporting) these great open source projects.

Next up: integrating Ivy (or Maven 2's Ant Tasks) for downloading dependencies. Hopefully both will still allow bundling JARs in a release so both AppFuse and Equinox can stick with the 1-download-to-get-everything philosophy. The main reason I'd like to integrate a dependency downloading tool is to reduce AppFuse's size in CVS, as well as make it easier to upgrade dependencies.

Trackback Spam

Roller seems to have done a pretty good job of suppressing comment spammers. The math question seems to trip up automated scripts and I only get about 1 or 2 spam comments per month. At least, I only see 1 or 2 per month - many get marked as spam and just sit in the database - never to be displayed. However, recently I've started to notice a lot of Trackback spam.

I dive into my "comment" table a few times a week to format comments so they look like their author intended them to look (I never alter wording). In the past couple of weeks, I've noticed a buttload of spam trackbacks (up to 10-20 per day). Here is an example. How do we go about stopping trackback spam? I'm guessing the easiest way is to disable trackbacks.

How do we get good designs for the CSS Framework?

I love the idea of Mike Stenhouse's CSS Framework. It's so simple: name the elements in your XHTML with a specific set of names, and then create your CSS to match that. The only problem with this framework is I haven't seen any good-looking designs on top of it. For good-looking design examples, see the CSS Zen Garden or Open Source Web Design.

While the CSS Zen Garden is nice, most of the designs are not useable for web applications. They're more of a showcase of what CSS can do, and often contain too many images for a real-world application or website. The designs from oswd.org, on the other hand, are perfect for web applications. However, the underlying HTML is different for each design.

So how do we marry the two? Maybe we should lobby some designers at oswd.org to use the CSS Framework for their designs? I think this would be a great asset to many communities - imagine what you could do with your Drupal theme if you didn't have to change your template files (only CSS). That'd be pretty cool.

Open Source CMS Evaluation - Part I: Installation

Today I began my journey in evaluating Open Source CMS applications. The motivation for this adventure can be found in my post titled "Building a website with an Open Source CMS". Basically, I'd like to find a good solution to build small-to-medium size websites. I want full-control over the design and features, and it shouldn't be too hard to configure, install or administer. I received many suggestions on my initial post, and thanks to these comments, I'm considering the following CMS solutions:

• Alfresco (Java)
• Daisy (Java)
• Magnolia (Java)
• Bricolage (Perl)
• MeshCMS (Java)
• AtLeap (Java)
• Mambo/Joomla (PHP)
• Drupal (PHP)

The reason OpenCms didn't make this list is because of Tim Howland's first demo (he left the link in a comment). As soon as he dropped into a shell, I gave up. I also tried OpenCMS a couple of years ago and couldn't get it to work. I still have a bad taste in my mouth from that experience.

Of this list, I was able to eliminate 3 options quite quickly: Bricolage, MeshCMS and AtLeap. Bricolage b/c their site was down for days when I first started looking at CMSs. In addition, it's written in Perl - of which I've never written a single line - and I don't feel like I'd be well suited to customize a Perl product. As for MeshCMS and AtLeap, both of these were eliminated b/c of the lack of mailing list traffic. This represents a small community IMO and I'd hate to start using a product that's not well supported or well documented. This is unfortunate b/c I could probably customize these products easier than the rest. Nevertheless, it's my customers that are important, not me.

This leaves me with three Java solutions (Alfresco, Daisy, Magnolia) and two PHP solutions (Joomla, Drupal). I'm not too keen on including Alfresco b/c I've never heard of it, but readers of my last post recommended it, as well as my colleague Bill Dudney (another friend who forgot how to blog). At first glance, there are a couple of major differences between the Java and PHP solutions. The Java ones definitely take the cake on download size:

• Daisy 1.3.1: 59 MB
• Magnolia 2.1: 13.4 MB
• Alfresco 0.6 (with Tomcat): 30.3 MB
• Joomla 1.0.1: 1.7 MB
• Drupal 4.6.3: 447 KB

Yes, large downloads is the nature of Java applications - but it's interesting to see the wide discrepancy b/c the 3 Java options listed here. In addition, it's a little disappointing that I can't download Alfresco standalone - why does it *have* to come with Tomcat or JBoss? Looking through the Tomcat directories and files - there doesn't seem to be any Alfresco-specific settings or files. Why can't I just download the WAR?

My goal in this session was to install these different CMSs and see which were the easiest to install - as well as which had the features I need to continue evaluated them. What I found was that Daisy is out of the running. This is primarily because it's a wiki, not a CMS. No wonder the JSPWiki guy was impressed with Daisy a few weeks back. Furthermore, the number of things you have to do to get Daisy installed is very long.

Magnolia, on the other hand, was very easy to install. Drop two WAR files into Tomcat and 10 minutes later you have a CMS. Yeah, that's a little scary - it took 10 minutes (647740 ms to be exact) to startup Tomcat after installing Magnolia. While I appreciate the easy installation, I'm still interested to see what kind of data store Magnolia is using. Is it using an embedded database or what? I didn't have time to look, but rather played around with the admin console a bit. I was very impressed with the admin console - even though I didn't figure out how to edit the homepage. It appears to be using Ajax everywhere. Right-clicking to edit a page even brings up an application menu (rather than a browser menu). Magnolia is impressive at first glance and will be included in Part II of my evaluation.

Alfresco, with a 0.6 release, was almost off my radar. The version number makes it seem like a very immature product - and the fact that it requires JDK 5 makes it seem even more immature. Upon startup, it spit out a number of errors - but they seem to be well documented in its "README_tomcat_linux.txt" file. I used OS X and despite the errors - everything appeared to be working OK. However, when I pulled up http://localhost:8080/alfresco, I immediately understood why Bill likes it. It looks like it's using JSF, and I'm willing to bet it's using MyFaces (he's a committer on the project). The disappointing thing I noticed after pulling up the initial page is that it's a login page. I'd expect to see a reader view initially rather than an admin view. After logging in, the interface seems very nice and easy to work with. However, after 30 seconds of clicking on stuff, I can't figure out how to get the reader view to show up - so I give up. I'm going to let this CMS graduate to Part II, but only because I didn't spend much time with it - and also because the UI looks quite polished.

I installed and played around with Daisy, Magnolia and Alfresco all in a 3-hour period today. First of all, I'd like to give props to all the authors of these OS projects as each was installable according to its instructions and I didn't have to google for a single setting. I installed Joomla and Drupal last week - both in under 10 minutes. Joomla was definitely more impressive - mainly because it's default homepage (note: this can change every hour) looks pretty cool. Drupal, on the other hand, is a bit more plain jane. This is not a bad thing necessarily - as it might be easier to design with a clean slate rather than remove-features, then-design. I did have to install PHP4 on my Mac to run both of these packages, but Server Logistics made that super easy. I also tried to install Joomla 1.0 on my Windows box (which has Apache 4.0.7 and PHP 4.3.3 from BlueGlue), but it failed halfway through the install with errors that my user/pass for the database were wrong. Not a big deal, but frustrating since it works fine on the Mac (and yes, the user/pass I'm using are correct).

Watch this space. Part II will address customizing each CMS to use an already-created theme, as well as playing around with each's features. I'd prefer a package that has built-in support for multi-author blogs - so that might make Magnolia and Alfresco look bad. However, I'm not going to hold it against them since I'm a Roller fan and committer. I don't mind using a 2nd application for blogging - especially if the built-in package is less than full-featured.

Conclusion: Alfresco, Magnolia, Joomla and Drupal are the easiest open source CMS applications to install (of the ones I looked at). Daisy was easy to install according to its instructions (of which there were many), but it's more of a Wiki than a CMS.

Update on Saturday at 1:00 p.m. - Based on reader's feedback to this post, I went ahead and installed three more: Plone, eZ publish (gotta love the domain name) and OpenCMS. All the previous CMS applications I installed on OS X, and I installed these 3 on Windows XP. I installed OpenCMS first, and while the setup was easy, it took 18 minutes to finish its importing of data. My Windows machine is easily 2x as fast as my PowerBook, so my guess is this would've been quite painful on the ol' Mac. Regardless, it's a one time wait-fee, so I can't really ding them for that. I played around with the Admin UI for about 5 minutes and found it extremely easy to use - as well as intuitive. I dig how you can view the content and edit it very easily. I never had to read any documentation to figure out how to work this system.

Next up was eZ publish. It took a bit of fiddling to get the installation to work. I had PHP 4.3.3 installed with Apache 2.0.47, and I upgraded to PHP 4.4 before trying anything. While setting up eZ publish, it told me it didn't work with 4.4, so I backed down to 4.3.3, after which it told me I needed at least 4.3.4. Thankfully, PHP is easy to install and upgrade on Windows and I got it all working fairly quickly. Of the three (and all the CMS's in fact), eZ publish has the nicest installer. The whole application and process gave me the feeling that it was the product I was looking for. It's designed to help you setup a website, and allows you to choose templates, features, etc. along the way. At the end, it stalls for a couple minutes - probably b/c it's creating everything and populating the database. The first thing I didn't like was the URLs (/index.php/feature). I wonder if that can be changed to be more path-based? Having an extension followed by additional slashes just doesn't seem right to me. From there, I logged in as an administrator and started playing around with things a bit. The Weblog feature seems very inadequate and doesn't even seem to support RSS. In addition, I couldn't figure out how to edit any of the templates in my browser. But the worst part was the admin UI was sssllloooowwww. It could have been b/c I had other stuff running, but I don't think so. eZ publish seems like a good system to recommend to friends who want quick and easy websites, but I don't think it's one for me.

The last CMS I installed was Plone. It was easy to install on Windows, but only b/c it has an all-in-one installer. I found it a bit strange that it doesn't install in a web server, but rather contains everything as part of the package. This includes Python, its own web server, and its own database (I'm assuming). It's an easy install, but I like the idea of installing a CMS into an existing web server rather than having a CMS with an embedded web server. The admin UI is simple enough to use, but it's very boxy and seems like it would be difficult to customize into a corporate or small business website. Please let me know if you feel this to be untrue (pointing to existing nice-looking installations would help). I didn't like the fact that it highlights members quite prominently, but that can probably be fixed with some good template-tweaking. The most disappointing thing I found was that I was unable to edit "skins" within the admin console. You have to download a separate package, customize it yourself, and then install it. What a pain, especially since I'd really like to be able to 1) modify template, 2) save and 3) view - just like this site allows me to do. For this reason, as well as the embedded server feature, I'm going to have to pass on Plone as well.

Conclusion 2: Alfresco, Magnolia, Joomla, Drupal and OpenCMS are the CMS applications I will continue to evaluate this weekend. I have to make a decision by Monday morning so I can start building a site with it. If any of these CMS'es don't allow me to customize its templates from a browser, please let me know so I can take it off my list.

Update on Sunday at 9:30 a.m. - I'm going to drop Alfresco and add MeshCMS for reasons stated here.

Seam

I have to admit, there's something about Seam that intrigues me. Maybe it's because they put up a really nice-looking demo (I'm a sucker for eye-candy), or maybe it's because it seems to be well documentated, or maybe it's the fact that it's based on J2EE standard technologies (EJB3 and JSF). It could also be that I greatly respect the work of Gavin King (who's always been respectful to me when I asked Hibernate questions back in the day).

It could be the lack of configuration, but I think it's the simplicity that gets me. A POJO (Entity Bean), a Session Bean for your business logic, and a view page (w/ Facelets no less, which is very cool). Other new frameworks this year include Wicket and Stripes. While these frameworks look cool, I really like the idea of a full-stack framework much better (I do use AppFuse after all). Well done Gavin - Seam looks very cool IMO.

On a related note, I upgraded AppFuse to MyFaces 1.1.0 yesterday w/ minimal effort. You can grab the latest from CVS if you'd like to get started with MyFaces quickly.