As you may gather from other entries in this blog, we've been working on a customer project which uses Flex for the client and Java for the server, with SOAP over HTTP in between. It worked well for us as a combination, because it minimised the number of new things to be learned - helpful when you're dealing with, er, aggressive delivery timescale aspirations. I've been having a few doubts about its long-term viability, though. SOAP's pretty verbose, and I'm not sure how quick the marshalling to/from XML is in ActionScript. Anyway, I was lucky enough to have a bit of spare time to investigate BlazeDS as an alternative, and thought I'd share some of the experience.

I downloaded BlazeDS and the sample applications to use as a guide in converting my existing web application. I'm not going to go into all the details here since that's not really the focus of this article - the Adobe BlazeDS Developer's Guide is well worth reading. Our server side code is a Spring application, so some extra work was required to make Blaze and Spring work together. Fortunately, Christophe Conraets has written an excellent article on the subject, along with some very handy sample code, which I have made use of.

Our server-side code is a Spring application, but there are a few minor peculiarities in the way it uses Spring 2 Security. The server is completely stateless, so the Flex client has to authenticate each request. For the SOAP version, we pass an authentication token in a custom HTTP header (Flex prevents you from accessing certain HTTP headers, the Authorization header included). In the BlazeDS version, I had to find another way of authenticating, since I couldn't see a way of getting access to the HTTP request that it uses to send the request to the server, so no way of adding my custom header.

When you set up a new Flex Project in Eclipse (either FlexBuilder 3 or the plugin), the new project wizard asks you if you want to use a remote object access service, such as LiveCycle Data Services (LCDS). You can use the same option to access BlazeDS services running in a J2EE server. It requires that you have your BlazeDS server running, because the next step asks you to enter the root folder and root URL of your server.

If you want to be able to compile your Flex project without the server running, you can get around this.

If you look at the documentation for the mxmlc compiler, you'll see that the context root and the location of the services definition file, services-config.xml (which are the two things the wizard is really after), can be specified as command line arguments. SilentWalker talks about using this with the Flex Ant tasks in his blog.