We recently switched from iReport to Jasper Studio and this is a very brief summary of what we had to do to make everything work in Jasper Studio as it did in iReport.
The first Part is about the Fields Provider.
Fields Provider are a thing of the past. You need to use
JRDataSourceProviders if you want to have the same features in Jasper Studio. Create a class as a subclass of JRDataSourceProvider. Implement the method "getFields". This is the very same method you´ve used in iReport. So you can pretty easily take your old code and put it there.
Afetr you´ve implemented your DataSourceProvider, put it in a JAR file and create a Data Adapter. Those Adapters are used in Jasper Studio to allow you to query your fields. Either create a data adapter using a generator (it´s just XML ...) or create it in Jasper Studio (by selecting JRDataSourceProvider). That´s it!
I will post a longer entry once I have more time.
If you have any questions, feel free to leave a comment.