GET_ENTITY&GET_ENTITYSET In Netweaver Gateway Odata

Hi All,

          I have two entities "WKXCC_COSTCENTER" and "WKXCC_USER".and I  want to associate them,one WKXCC_COSTCENTER , a collection of "WKXCC_USER".But now,I must enter a parameter called 'costcenter number' and I need to get_entityset. From the picture below we can see the method "get_entityset" don't allow to enter parameter,and when I enter a parameter,the method calls 'get_entity' automatically and only read my first line information.

I want to make a association between "WKXCC_COSTCENTER" and "WKXCC_USER",and this is my codes:

After do that I back to visit my interface(url),and I find noting in it.

what should I do to modify my codes?

Thanks in advance!!!!!