Deploying multiple wars within an ear (including web services) - pls advise

Question

**Apologies - this post also appears in the standard Java forums, before I realised there was a separate Enterprise forum!**
Hello all
I am working on an application that receives XML messages from sending systems, processes them and forwards them to receiving systems. There is a set of rules concerning who can send what to who. The entry and exit points to the application are web services.
I would be very grateful for some general advice on best practice for packaging this application. I have done a lot of browsing and read some articles, but I understand the whole picture has changed recently with the growing popularity of web services and that many of the articles I have read are probably out of date.
The whole thing could be packaged into a single war, but it would be ideal to treat the different components separately as in the future they may be modified and deployed separately. I therefore envisaged having 3 wars in an ear as follows: -
a. A set of incoming web services to receive messages from the sending system. This is like a hook into b (below). The sending systems will be clients to these web services.
b. A web application that takes the messages from a and processes, authenticates and transforms them.
c. A set of outgoing web services that sends the message on to the receiving system. These will be like facades to the receiving systems and b will be a client to them.
The whole thing would then work in reverse to process the response.
A few questions: -
1. I know I haven't given much info here, but does this seem like a reasonable basic packaging strategy? Any other suggestions?
2. Is it good practise to package multiple wars together into an ear? If anyone could send me an example ant script that does this, I would be so grateful.
3. Wars a and c above will both need to have full visibility and access to b, which is the "brains" of the whole thing. How is this best achieved when packaging?
4. If you could point me in the direction of a best practice guide, examples or tutorials, I would be very grateful.
Many thanks for taking the time to read my post - and for any replies.
Kind regards
Jon

Answer 1

That is a viable method to package your application, pending the architecture of your application supports this.
Each WAR file will be packaged as a seperate web application and all web applications on that web server will be able to communicate with each other over sockets by having the URL of the web component that you wish to communicate with. This interface needs to be there mind you.
EAR files are generally deployed to an application server so if you happen to have an application server like Weblogic or Websphere then this would be an ideal setting for hosting your application. Packaging in an EAR file and also hosting on an application server gives you the benefit of using J2EE constructs, like EJB's to provide an alternative means of communication between different web components.
Packaging seperate wars into an ear file really wouldn't work out too well with just a standard servlet container like Tomcat.