I am working in Eclipse on a Google AppEngine Java code. Every time I save a java file, the DataNucleus Enchancer starts off \"Enhancement of Classes\". Its quite irritating
This won't solve the focus problem, but it will reduce how often the enhancer runs:
You can configure the enhancer to only enhance certain files. You can specify a pattern based on packages or class name. To specify the pattern, click the project menu, then properties, then google, then app engine, then ORM. If you name your persistent classes with a common suffix, you can specify a pattern like "*Entity.java"
The Enhancer is setup as a Builder in your project properties. I suspect you could safely disable it while you are editing, and then when you want to run it you would have to re-enable and build again to ensure that any changes you made to persistent classes are reflected correctly before you try to run or test your application locally. Then, you could upload to app engine.
You can restrict which classes DataNucleus watches for changes so that it only re-runs the enhancement when your model classes actually change.
Go to the Project's properties, and select Google->App Engine->Orm. There you can specify patterns for the files to watch.
For example, I put all my model beans in a model/ subdirectory, so a pattern of src/**/model works for me. There are also example patterns under the 'Add' dialogue.