I have created a little demo to show how to integrate Ext with Java/Spring/DWR. I took the DWR Proxy/Reader that has been posted in the forums and modified it a bit. For example I have a boolean flag that can be passed when you construct a DWR Proxy. This will allow you to indicate if you want to support paging and remote sorting. In case you do your service methods that you expose via spring/dwr will need three additional parameters. But if you don't want to support paging and remote sorting you can leave those parameters out.
The DWR Reader also supports nested properties. For example if you are returning a customer object that has an address object within it.
Here is the url java-ext.zip.
The download is a about 3.5mb but includes everything you need: ext 1.0, dwr, spring, sample code. An ant build file is also included but you may need to modify the build.properties file for your environment.