Gateway service with multiple entity sets

Hi,

I have designed a Gateway service with 3 entities, and 3 entity sets.Entity sets are not related one to another. This entity sets correspond to static data stored in 3 different custom table in SAP. The aim of this service is to provide static data (but customizable on the backend) for drop down lists on a SAP UI5 application consuming Gateway services.

I am wondering if it is possible through a single read operation, to retrieve all entity sets. Since the service URL to get data related to one entity set is /sap/opu/odata/sap/ZTEST_SERVICE_SRV/EntitySet, how should I process if I want to retrieve all 3 entity sets ? Is it something possible or do we have to call each entity set at once ?

Thanks in advance for your help.

Thibault