Customers don't need to implement domains with a resource bundle. They could just as easily use java constants. Labels however, must be localizable, so it makes sense for them to do it this way. The generated naming convention for domains is <Entity>Domains.properties. These are generated to the service layer impl code package (alongside the code that uses them). An example of a domains file is shown below
readDtls.clientDtls.name=FULL_NAME readDtls.sportingActivityType=SAMPLE_SPORT_ACT_TYPE readDtls.sportingAwardType=SAMPLE_SPORT_AWRD_TYPE readDtls.paymentAmount=CURAM_AMOUNT readDtls.startDate=CURAM_DATE readDtls.endDate=CURAM_DATE readDtls.comments=COMMENTS