With Spring Data REST, how to make custom queries use the HATEOAS output format?

Question

I'm learning the Spring 4 stuff by converting an existing Spring 3 project. In that project I have a custom query. That query fetches data in a straightforward way, after which some heavy editing is done to the query results. Now the data is sent to the caller.

I plan on extending CrudRepository for most of my simple query needs. The data will be output in HATEOAS format.

For this custom query I think I should be adding custom behavior (spring.io, "Working with Spring Data Repositories", Section 1.3.1, "Adding custom behavior to single repositories").

As an example:

@Transactional(readOnly = true)
public List<Offer> getFiltered(List<Org> orgs, OfferSearch criteria) {
    List<Offer> filteredOffers = getDateTypeFiltered(criteria);
    filteredOffers = applyOrgInfo(orgs, filteredOffers);
    filteredOffers = applyFilterMatches(filteredOffers, criteria);
    return sortByFilterMatches(filteredOffers);
}

(The code merely illustrates that I don't have a simple value fetch going on.)

If I could use the raw results of getDateTypeFiltered(criteria) then I could put that into a CrudRepository interface and the output would be massaged into HATEOAS by the Spring libraries. But I must do my massaging in an actual Java object, and I don't know how to tell Spring to take my output and emit it in my desired output format.

Is there an easy way to get there from here? Or must I try things like do my filtering in the browser?

Thanks, Jerome.

score 0 · Answer 1 · answered Sep 19 '15 at 23:46

0

I am not sure I perfectly got your question. If I did this should be the answer: http://docs.spring.io/spring-data/jpa/docs/1.9.0.RELEASE/reference/html/#repositories.custom-implementations

answered Sep 19 '15 at 23:46

Luca Abbati

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5
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Your reference is much like to the one I alluded to in my question. I understand that I *can* write my query by that means. What I am not understanding is how the HATEOAS format gets wired into the results. I'm beginning to get the impression that in the simplest example the Spring Data library actually is called directly by the Spring servlet. Perhaps I will have to experiment after all. – Jerome P Mrozak Sep 20 '15 at 01:43

score 0 · Accepted Answer · answered Sep 23 '15 at 22:13

To properly get HAL formatted results, your query controllers must return some form of Spring HATEOAS Resource type.

@RequestMapping(method = RequestMethod.GET, value = "/documents/search/findAll")
public ResponseEntity<?> findAll() {

    List<Resource<Document>> docs = new ArrayList<>();
    docs.add(new Resource<Document>(new Document("doc1"), new Link("localhost")));
    docs.add(new Resource<Document>(new Document("doc2"), new Link("localhost")));

    Resources<Resource<Document>> resources = new Resources<Resource<Document>>(docs);

    resources.add(linkTo(methodOn(ApplicationController.class).findAll()).withSelfRel());
    resources.add(entityLinks.linkToCollectionResource(Document.class).withRel("documents"));

    return ResponseEntity.ok(resources);
}

I have submitted a pull request to Spring Data REST to update its reference docs to specify this in http://docs.spring.io/spring-data/rest/docs/2.4.0.RELEASE/reference/html/#customizing-sdr.overriding-sdr-response-handlers

With Spring Data REST, how to make custom queries use the HATEOAS output format?

2 Answers2