Java Spring REST API Handling Many Optional Parameters

Question

I\'m currently messing around with a Spring Boot REST API project for instructional purposes. I have a rather large table with 22 columns loaded into a MySQL database and am

Answer 1

You can do this easily with a JpaSpecificationExecutor and a custom Specification: https://spring.io/blog/2011/04/26/advanced-spring-data-jpa-specifications-and-querydsl/

I would replace the HashMap with a DTO containing all optional get params, then build the specifications based on that DTO, obviously you can also keep the HashMap and build the specification based on it.

Basically:

public class VehicleFilter implements Specification
{
    private String art;
    private String userId;
    private String vehicle;
    private String identifier;

    @Override
    public Predicate toPredicate(Root root, CriteriaQuery query, CriteriaBuilder cb)
    {
        ArrayList predicates = new ArrayList<>();

        if (StringUtils.isNotBlank(art))
        {
            predicates.add(cb.equal(root.get("art"), art));
        }
        if (StringUtils.isNotBlank(userId))
        {
            predicates.add(cb.equal(root.get("userId"), userId));
        }
        if (StringUtils.isNotBlank(vehicle))
        {
            predicates.add(cb.equal(root.get("vehicle"), vehicle));
        }
        if (StringUtils.isNotBlank(identifier))
        {
            predicates.add(cb.equal(root.get("identifier"), fab));
        }

        return predicates.size() <= 0 ? null : cb.and(predicates.toArray(new Predicate[predicates.size()]));
    }

// getter & setter
}

And the controller:

@RequestMapping(value = "/{ticket}/count", method = RequestMethod.GET)
public long getItemsCount(
    @PathVariable String ticket,
    VehicleFilter filter,
    HttpServletRequest request
) throws Exception
{
    return vehicleService.getCount(filter);
}

Service:

@Override
public long getCount(VehicleFilter filter)
{
    return vehicleRepository.count(filter);
}

Repository:

@Repository
public interface VehicleRepository extends JpaRepository, JpaSpecificationExecutor
{
}

Just a quick example adapted from company code, you get the idea!