Spring Integration 2.2 to 3.0 Migration Guide

##MessageGroupCallback

This interface is now an inner interface of MessageGroupStore; everything remains the same, just change the import.

##integrationConversionService

Spring Integration no longer does fall back to the BeanFactory's ConversionService, however there is still falling back to the creation of DefaultConversionService where it is appropriate, if there is no registered integrationConversionService bean. If there is really a reason to use conversionService as integrationConversionService, it's just enough to add one more line to the Application Context:

<alias name="conversionService" alias="integrationConversionService"/>