Question

I want to add sorting to a HTML table populated by Hibernate. The actual sorting has to be done by a database. To feed “Order by” condition to the database Java has to match passed sort parameters to a column in a query. I’m unsure how to implement this matching.

I could pass something like “Employee.salary” but then this condition need to be checked like all parameters passed from client. This check would require getting column name from Hibernate annotations, and this is not easy I guess. Also, the column can be query-specific and not corresponding to a table field.

Another way is to use hardcoded values in a presentation layer. But this will tie presentation layer with a persistence layer, which is also not good I think.

How do you deal with server-side sorting in web applications?

Answer 1

If I have an Employee entity, then I want an EmployeeRepository that lets me findEmployeesBySalary(SortType sortType, int skip, int limit)

From the web service side, I want a URI like

foo.com/employees?by=salary&skip=10&limit=50

which returns something like (as a AJAX XHR call)

<employees>
    <employee uri="/employee/1" />
    <employee uri="/employee/2" />
    <employee uri="/employee/3" />
</employees>

or the full-blown HTML page rendered appropriate.

This conveniently allows caching of employees on the client side (which the cache size being flexible) and at the HTTP level.

Note that, column names? Irrelevant. You would have a HiberateEmployeeRepository that implements the EmployeeRepository interface as needed. Express this stuff as methods, and use complex parameters if you need to.

You could even have two separate methods if you want, rather than an enum, findHighestPaidEmployees and findLowestPaidEmployees – foo.com/employees?salary=lowest&skip=10&take=30 mind you, that’s a horribly depressing URI.