Showing posts from June 24, 2012

Counting the rows returned from a JPA query

Despite being almost ten years old, the JPA specification to this day has rather poor support for basic paging/sorting/filtering. Paging/sorting/filtering is used in a lot of (CRUD) applications where the result from a query is shown in a table, and where the user can scroll through the results one page at a time, and where this result can be sorted by clicking on any of the table column headers. In order to support this a number of things are generally needed: The total number of rows (or entities) in the full result must be known There should be support for an offset in the full result and a limit for the amount of rows that will be obtained The column (attribute) on which to sort must be dynamically added to the query Search expressions must be dynamically added to the query As it appears, only offset/limit is directly supported in JPA. A sorting column can only be added dynamically when using the overly verbose and hard to work with Criteria API. Search expressions are som…