J2ME Design pattern

[Ole Kristian]

Hi!
I'm wondering if there are any design patterns which is suitable for the j2me technology(CLDC/MIDP)?
The system I'm about to design has these characteristics:
- The client-side appliction is a travel expense report application. This application will be installed on a PDA (Palm or Pocket PC). The challenge will be to design a system which is more or less independent of the device, i.e. not to use any device-specific properties (only soft button, etc).
- The appliation must be able to communicate with a server-side application residing on a PC through the PDA cradle.
So if any of you have links or books you want to recommend about j2me design patterns, I would appreciate if you told me about them

[Mark Spritzler]

I don't know much about specific Patterns for J2ME
However, I am familiar with things that would lead to patterns.
For instance, we know that the memory for a mobile unit is small, and therefore try to limit what is done on the client, but also really limit all the calls to outside help. If you are continually calling a web server or other server for services, the traffic really slows things down.
So what that leads to is using things like Proxy, Adapter, and Facade patterns on the client side, and Coarse designs on the server side. Coarse meaning instead of three calls to get three data pieces from the server, it can be done in one call to the server that returns a Collection or Text of all the data returned in from the one call.
Obviously, my statements are on the higher level thought process of design, and applications require specific ways of implementation, but keeping those thoughts will keep things cleaner for you.
Hope that helps, and that I am not completely off course in my advice. But I am sure if I am that someone else will clear it up.
Mark

[Michael Yuan]

I think J2ME design pattern is an very interesting topic. For starters, there is the Sun Smart Ticket Blueprint:
http://java.sun.com/blueprints/code/index.html#java_smart_ticket_demo
If you are more interested in MIDP UI patterns, I would recommend Ben Hui's article on JavaWorld
http://www.javaworld.com/javaworld/jw-12-2002/jw-1213-j2medesign.html
I will give a talk in this upcoming JavaOne conference and it will focus on "best practices and design patterns for J2ME". So, if you do go there, check out my name in the session list!