Searching in column of reference table

[tejprakashmittal]

public class Employee {
@id private int id;
private String firstName;

@ManyToMany(cascade = CascadeType.ALL)
@JoinColumn(name = "id_office")
private Set<Office> office = new HashSet<>();

}

class Office {

@Id @GeneratedValue private int id;
private String city;

}

Considering above declaration of classes, how to implement Advance section of the given datatable example.

Advanced searchpanes section -

how to implement the following,

$('select#officeSelector').change(function() {
var filter = '';
$('select#officeSelector option:selected').each(function() {
filter += $(this).text() + "+";
});
filter = filter.substring(0, filter.length - 1);
table.column(7).search(filter).draw();
});