sap ui5 error "In the context of Data Services an unknown internal server error occured"

Hi SapUI5 experts,

I have trying to pull data from sap database using oDataservice,

I have created data provider class and implemented it along with model provider class,

when I test oData service, Service will be initiated, even i can check metadata which is displayed correctly.

but when i try to test for data from entityset  i encounter error "In the context of Data Services an unknown internal server error occured".

but data provider class  is fetching data but its not passed to browser.

Please help we in resolving this error.

Thanks,

Vishwanath S