As a follow up to my article on automating XML updates, I’d like to report that I did use Excel and Perl’s XML::Twig to successfully generate XML descriptors for my web service consumer, and it was a lot easier than I thought. I’m using XFire 1.2.6 web services stack running under JBoss and using MyEclipse IDE 5.0. I’m happy to say I went from blank spreadsheet and no plan to generated XML files from spreadsheet values in one and half hours. The implementation is of course expandable and reusable. This implementation should work for WebSphere and .NET as well.

I needed to create different configurations for my web application so that the service request went to different endpoints for different environments. The endpoint is at an enterprise service bus (ESB) and there is a different ESB for each environment. I need to have my ‘dev’ instance of the consumer hit the ‘dev’ instance of the ESB, the ‘qa’ instance of my web app hit the ‘qa’ instance of the ESB, etc. We’ve set up Meister to pick up the correct XML file for the target environment for the build of the WAR.

I started by setting up the spreadsheet as follows. I had an unnecessary column for Host indicating JBoss, but I hope to include WebSphere and maybe .NET as well some day. My web app actually connects to two services a.k.a. providers, so there is a column there. And, next is the configuration label for my web app with the name corresponding to the environment it is designed for. So, the first three columns of the spreadsheet look like:

 

Then I needed a way to indicate the resource that would change. Right now I only have XML files, but I chose to stick with a generic URL for that. Unlike Maven or Ant generators, we start with an XML file that actually works and has been tested - not some hacked up parameterized version that takes additional effort to create. The fourth column of the spreadsheet looks like the following (with repeated entries omitted):

 

Next, I needed a way to specify a target location to change within the XML file. Now, I know I’m going to use XPath, but I’ll want this to one day work for properties files as well, so I came up with a URL-like thing called a Universal Datum Locator (UDL) which pre-pends the method of locating the datum to change on to a method-specific locator. It could be a property name, an XPath or a Perl regex, for example. In this case it is XPath and then the last column contains the replacement value for the datum indicated by the UDL. XPath is also very intuitive and easier to construct than it may look.

The value for the UDL looks like:

xpath://beans/bean[@factory-bean=’xfireProxyFactory’]/ constructor-arg[@index=’1′]/value

So the fifth column contains the UDL’s, which in my case is always the same XPath expression. The final column of the spreadsheet contains the replacement value of the datum indicated by the UDL:

 

My nifty Perl script is only about 80 lines of real code and because XML::Twig is nearly the best thing in the world, I pass the entire XPath in as a hash key to modify the source XML file:

my $twig = XML::Twig->new(

pretty_print => ‘indented’,

twig_handlers => {

“$xpath” => sub {

$_->set_text($new_datum);

}

}

);

Here, “$xpath” is directly from the “UDL” column of the spreadsheet with only the ‘xpath://’ stripped off and “$new_datum” is directly from the “Value” column. That’s a pretty useful one line subroutine if you ask me. I had the new XML files each generated into a different folder (dev/,int/, etc). Then, I checked them into version control (CA Harvest) and built each of them with Meister. If you want the full code, let me know and I’ll post it somewhere.

I did find working with the Excel 2003 XML Spreadsheet format a tiny bit awkward. You have to keep track of the column and row indices, but not bad other than that. I see Microsoft Word 2007 allows you to save as an XML document directly, but you apparently have to define bindings. I’ll have to check that out.

When you work with a locking-type version control tool like CA Harvest, your Meister build project will appear in your Eclipse workspace as read-only when you check out an existing workspace. I’ve been using Eclipse for WebSphere development (WebSphere Studio Application Developer) and for JBoss via MyEclipse IDE. If you want to regenerate your Java targets, you first have to check out the Meister build project so that the files are writable.

Since this can lock the targets exclusively and prevent others from updating the target, you may not want to check out the build project, but you may still want to develop freely and update your local targets for Meister to build it. For this situation I recommend creating a separate build project that you may never check in to version control. It will be writable and it allows you great freedom for a maximally agile development environment. The ‘official’ build project may reference all the built archives in the workspace, but having your own local build project can allow you to focus for a unit build. For example, my workspace may contain an EAR project, a WAR project and one or more JAR projects. If I am principally working only on one of the JAR projects, my local build project can reference only that one JAR project.

When it’s time to release your JAR code updates to the system build and test environments, synchronize your workspace and check out the VC build project. Generate your targets, do a local system build and then check everything in. Your team system build will work fine!

I wanted to share a specific benefit I enjoyed while using Meister for Java development. As part of my role to help develop an automated JBoss build and deploy system, I ended up taking on a developer role for a web services security project for both JBoss and WebSphere. While the project involved about 1000 lines of Perl, it also got me writing simple web services and consumers for JBoss and WebSphere and building them using Meister and its Eclipse plug-in.

Believe it or not, I am still using WebSphere Studio Application Developer 5.1. While my specific tale involves that IDE, it is equally applicable to MyEclipse and Rational Application Developer set of Eclipse IDE’s. In my environment, CA Harvest is the version control/SCM tool and Meister is the build tool. After code is checked in from my desktop using the CA Harvest eclipse plug-in, the code is replicated out to a Linux server, where Meister performs the official system build that is sanctioned for deployment to the application server. There is also a Meister Eclipse plug-in that scans the WSAD workspace for build targets and dependencies. Meister stores this information in one XML file per build target and those files are also checked in to CA Harvest right along side the source code.

Working intensely within the WSAD Eclipse environment as the project manager cracked the whip, I worked with a consumer application and updated it according to the changes in the service WSDL and service endpoint URL’s. One thing I learned is that if one of the parameters for the consumer is tweaked, don’t bother tweaking the XML or generated code, just regenerate the whole client. WSAD will even check out the files before if they need to be. So everything looked good on my desktop with the service and consumer deployed to two separate WebSphere servers on ports 9080 and 9081. Now to get it into the enterprise ‘dev’ environment…

Using the ‘Generate Target Definitions’ feature of the Meister plug-in I updated the Meister build target XML definition files and checked in all my code. I then promoted the code in CA Harvest which automatically kicked off a ‘dev’ build in the Linux environment. I got an error back from Meister saying ‘jdmpview.jar’ doesn’t exist.

Since I knew my consumer app and its elementary nature, I knew that jdmpview.jar wasn’t one of my JAR’s and it must be one of WebSphere’s. Given that 200 other Java apps use the same build environment with the same standards, I probably didn’t use some new feature of WebSphere that no one else is using. Therefore, it must a problem on my local desktop with the version of JVM I was using.

Sure enough, the consumer app was using the base_v51 WebSphere runtime instead of the ee_v51. (I did inherit the initial version of the app from someone else!) And, oddly enough, there is an extra JAR in the base that is missing in the more fully featured Enterprise Edition. Meister correctly forced the runtime environment to be EE for the Linux build, overriding the developer selection. I switched the runtime in the Java build path properties, regenerated the Meister target definitions, checked them in and promoted them to a successful ‘dev’ build. Regenerating the target definitions had the effective of switching out the list of JAR files in the library path from the base_v51 set to the ee_v51 set. The whole thing including one bad and one good build took about 4 minutes.

The great benefit for me was the balance between developer and SCM functions. We could have applied more controls at the desktop level, but from my perspective, I prefer an Agile environment with more freedom even if it means occasionally hanging myself with my own rope. In this scenario I let the tools dot the I’s and cross the T’s and it took no more time than say, waiting for Outlook over VPN.