How to create custom native query in spring data rest without duplicating their ResourceAssembler?

Question

I have a controller that looks like that

@RestController
public class LocationsController {

    @Autowired
    private EntityManager manager;

    private String withinQuery =
            "WITH L as\n" +
            "\n" +
            "(SELECT *\n" +
            "FROM location\n" +
            "\n" +
            "WHERE ST_Distance(ST_FlipCoordinates(location.shape), ST_FlipCoordinates(ST_GeomFromGeoJSON('%s'\n" +
            "        )))=0)\n" +
            "\n" +
            "SELECT *\n" +
            "FROM L\n" +
            "WHERE id NOT IN (\n" +
            "SELECT metalocation_id FROM location\n" +
            "WHERE metalocation_id IS NOT NULL\n" +
            ")";

    private String nearestQuery =
            "select * from location order by ST_Distance(ST_FlipCoordinates(location.shape), ST_FlipCoordinates(St_GeomFromGeoJSON('%s'))) limit 1";

    @RequestMapping(value="near", method = RequestMethod.GET)
    public List<Location> getNearestLocations(@RequestParam(value = "point") String pointAsString) throws IOException {
        List<Location> locationCloseToPoint = manager.createNativeQuery(String.format(withinQuery, pointAsString), Location.class).getResultList();
        if (locationCloseToPoint.size() == 0) {
            List<Location> closesLocation = manager.createNativeQuery(String.format(nearestQuery, pointAsString), Location.class)
                    .getResultList();
            locationCloseToPoint.addAll(closesLocation);
        }
        return locationCloseToPoint;
    }
}

As you can see it return list of locations.

@Entity
public class Location {

    public Geometry getShape() {
        return shape;
    }

    public void setShape(Geometry shape) {
        this.shape = shape;
    }

    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    private Long id;

    @NotNull
    private Geometry shape;

    @ManyToOne(cascade = CascadeType.ALL)
    private Location metalocation;

The problem with that is I want to return this list in format that spring data rest uses for location resource with all hateoas fields and stuff. More specifically I want to have a link to metalocation in the output.

I've read about spring-hateoas and ResourceAssembler and @RepositoryRestController and I think I could replicate what spring-data-rest is doing via writing custom ResourceAssembler, but I don't want to, because you know, why would I want to write the code that is already written by spring-data-rest, right?

They doing all this assembling stuff automatically, right? Because I see it in the http output. So I think there should be a way to use it.

Mathias Dpunkt · Accepted Answer · 2015-11-20 21:41:07Z

1

You can try the following.

First annotate your controller with @RepositoryRestController instead of @RestController.

You can then use the resource assembler that spring data rest uses internally - PersistentEntityResourceAssembler

The example below works for me.

@RepositoryRestController
public class DemoController {

    private final ProductRepository productRepository;
    private final PagedResourcesAssembler<Object> pagedResourcesAssembler;

    @Autowired
    public DemoController(ProductRepository productRepository,
                          PagedResourcesAssembler<Object> pagedResourcesAssembler) {
        this.productRepository = productRepository;
        this.pagedResourcesAssembler = pagedResourcesAssembler;
    }

    //use PersistentEntityResourceAssembler and PagedResourcesAssembler to return a resource with paging links
    @RequestMapping(method = GET, path="/products/search/listProductsPage", produces = HAL_JSON_VALUE)
    public ResponseEntity<PagedResources<PersistentEntityResource>> getAllPage(Pageable pageable, PersistentEntityResourceAssembler persistentEntityResourceAssembler) {
        Iterable<?> all = productRepository.findAll(pageable);

        return ResponseEntity.ok(pagedResourcesAssembler.toResource((Page<Object>) all, persistentEntityResourceAssembler));
    }

    //return Resources of entity resources
    @RequestMapping(method = GET, path="/products/search/listProducts", produces = HAL_JSON_VALUE)
    public ResponseEntity<Resources<PersistentEntityResource>> getAll(Pageable pageable, PersistentEntityResourceAssembler persistentEntityResourceAssembler) {

        return ResponseEntity.ok(new Resources<PersistentEntityResource>(productRepository.findAll().stream()
                .map(persistentEntityResourceAssembler::toResource)
                .collect(Collectors.toList())));
    }
}

The getAll method is probably what you want.

I added also the getAllPage variant that converts a Page into a PagedResource - this is what spring data rest generates if you get a collection resource. Here you also have to use PagedResourcesAssembler to generate the page links.

Is this what you are searching for?

In your case I would also try to avoid the custom controller - If you could express your native query as a repository finder, spring data rest would automatically expose the finder. Spring data jpa seems to support native queries via annotation - http://docs.spring.io/spring-data/jpa/docs/1.9.1.RELEASE/reference/html/#jpa.query-methods.at-query

edited Nov 20, 2015 at 21:41

answered Nov 20, 2015 at 19:30

Mathias Dpunkt

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5 Comments

Mathias Dpunkt Over a year ago

Just saw that you are not using the Page at all . so in your case it would be enough to go over your list and use PersistentEntityResourceAssembler to convert each item in your list.

user1685095 Over a year ago

Thanks, I was able to find that I can use PersistentEntityResourceAssembler and tried to return List<PersistentEntity> but that gaved me not found error despite the list of persistent entities was correct. So, I would appreciate if you also would give some links to the documentation where I can read why it's actually working. Thanks!

Mathias Dpunkt Over a year ago

What I was trying to show in my example code is that you should not return a List of your entity. You need to return a Resource - Resources<PersistentEntityResource>. The use of PersistentEntityResourceAssembler is not documented as far as I could see.

Mathias Dpunkt Over a year ago

Just edited my answer - please see the last paragraph for a suggestion on how to change your solution idea.

user1685095 Over a year ago

While I could use @Query annotation for both of the queries, as you can see I still need a controller, because there is a logic there. If the first query returns empty, then and only then I need the second query. I can express then with postgres stored procedure, but I don't think that this is the way to go.

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