Sorting the Data Tables column, which is a foreign key reference.

THE ROCK

I created my application using Jhipster and using Data Tables and Anguar js, I created two entities Office and Employee, in Office tables i have office Id, Office address and office name and in Employee table i have employee id, employee name, employee address and office id as foreign key. and i created data tables for office entity and employee entity and in employee data table i'm displaying employee name, address and Office name. so pagination, search and everything works fine. but sorting on the column Office name column in the employee table is not working and it is throwing** array index out of bound exception on the back-end. and when i click on the for the sorting alert popup says **"DataTables warning: table id=DataTables_Table_6 - Ajax error. For more information about this error, please see http://datatables.net/tn/7", how can i make sort working the Office name column in employee data table