Configure controller in a way that optional sorters can be enabled/disabled based on the controller's input

Question

I am trying to write an endpoint that allows the use of optional sorters in the backend.

For example, I have a sorter that allows me to sort elements in a list - which is what my endpoint's controller returns - based on their creation date.

If the corresponding controller parameter is true then the elements are sorted started from the newest and moving towards the oldest.

If the corresponding parameter is false, then the opposite.

This is a Spring Boot project.

I was wondering if there is a more spring-appropriate way to achieve this?

This is my controller:

@RestController
public class StudentsController{
    @Autowired
    private GradeBook yearlyGrades;

    @GetMapping("/successful")
    public List<Student> getSuccessfulStudents(
        @RequestParam(name = "startDate") Instant startDate,
        @RequestParam(name = "endDate") Instant endDate,
        @RequestParam(defaultValue = "false", required = false) boolean sortStartingFromHighestGrade,
        @RequestParam(defaultValue = "false", required = false) boolean sortStartingFromEarliestDate) {


        return this.yearlyGrades.getSuccessfulStudents(startDate, endDate, 
                                                       sortStartingFromHighestGrade, 
                                                       sortStartingFromEarliestDate);
    }
}

Depending on the true/false value of the last two parameters:

sortStartingFromHighestGrade
sortStartingFromEarliestDate

Different processing happens in the background in the service class.

catch23 · Answer 1 · 2020-05-23T19:58:45.923

You could implement sorting with spring with Pageable support.

You will create a Pageable object for getting the data from DB.

You could use PagingAndSortingRepository for Spring Data:

public interface StudentRepository extends PagingAndSortingRepository<Student, Integer> {

And call regular .findAll(pageable) with any Sorting option for your entity at the service layer.

And your controller will look something like:

@GetMapping
public Page<Student> getSuccessfulStudents(
        @RequestParam(name = "startDate") Instant startDate,
        @RequestParam(name = "endDate") Instant endDate,
        @RequestParam(value = "page", required = false, defaultValue = "0") int page,
        @RequestParam(value = "size", required = false, defaultValue = "10") int size) {
    return yearlyGrades.getSuccessfulStudents(startDate, endDate,
                 PageRequest.of(page, size, Sort.by("propertyFromClass")));
}

If you don't want to return Page<Entity> you could convert it to List at the service layer.

UPDATE:

Instead of creating Pageable object by PageRequest.of(), you could pass it directly by URL:

/successful?page=0&size=10&sort=grade

where grade is a field from Student class.

or

/successful?page=0&size=10&sort=grade,ask

All parameters internally recognize by Pageable as following:

page - Page number

size - Page Size

sort - sort by (Order by)

direction - ASC / DESC

Then your controller should be:

@GetMapping("/successful")
public Page<Student> getSuccessfulStudents(
    @RequestParam(name = "startDate") Instant startDate,
    @RequestParam(name = "endDate") Instant endDate,
    Pageable pageable) {
    return yearlyGrades.getSuccessfulStudents(startDate, endDate, pageable);
}

Useful references:

Spring Data Pagination Sorting

score 0 · Accepted Answer · answered May 21 '20 at 13:46

Spring can come handy in multiple ways here:

From the point of view of Spring MVC you don't have to supply all request parameters in separate variables, Instead you can define a class with all these parameters and spring will map them for you:

public class Params {
  private Instant startDate;
  private Instant endDate;
  private int page = 0;
  private int size = 10;
  ... constructor/getters/setters ...
}

Then in your controller you can do the following, IMHO, looks more clean:

@GetMapping
public Page<Student> getSuccessfulStudents(Params params) {
   ...
}

As @nazar_art has mentioned, you can use Pageable support of spring data if you have spring data Otherwise you'll have to implement it by youself, which is not a big deal anyway.

score 0 · Answer 3 · answered May 24 '20 at 03:17

If processing on the backend is really different, then you can define different endpoints with the same path but different params field which allows defining additional conditions, see @GetMapping annotation docs and example in create two method for same url pattern with different arguments

score 0 · Answer 4 · answered May 24 '20 at 20:58

if you are asking at API level then this is not related to Spring but rather to REST API design and here multiple notations can be used

GET ...&sort=+grade and GET ...&sort=-grade
GET ...&sort=grade.asc and GET ...&sort=grade.desc
GET ...&sort=asc(grade) and GET ...&sort=desc(grade)

for more params

GET ...&sort=+grade&sort=-age
GET ...&sort=+grade,-age

for spring part take a look at https://docs.spring.io/spring-data/commons/docs/current/api/org/springframework/data/domain/Sort.Direction.html and https://docs.spring.io/spring-data/commons/docs/current/api/org/springframework/data/domain/PageRequest.html

Configure controller in a way that optional sorters can be enabled/disabled based on the controller's input

4 Answers4