Criteria query.list() returns results but item in the List is null

[mail2bansi]

Criteria query.list() returns results as expected but the item in the List is null when working with pojo having composite key .
But if i remove the composite key and make the dataId field be the key the
problem was resolved (both query and criteria work).

Here is the code snippet with composite key

public class DeviceSummaryView  implements java.io.Serializable {
   // Fields    

     private DeviceSummaryViewId id; //Composite Key
     private String tagNumber;
...
...
...
}
public class DeviceSummaryViewId  implements java.io.Serializable {
    // Fields    

     private Long deviceId;
     private long interfaceId;
     private Long ipId;
     private Long hostNameId;

}

Any pointers/suggestions to make Criteria query work with Composite key will be highly appreciated

Regards
Bansi