Spring Data Rest and excerpt Projections

Question

I am using the inlineAddress sample of the Spring Data Rest documentation.

/persons return the address inline as expected.

Now I add a projection to the AddressRepository

@RepositoryRestResource(excerptProjection = AddressProjection.class)

Which is as below

@Projection(name = "AddressesProjection", types = Address.class)
public interface AddressProjection {

public String getStreet();
}

This is causing the /persons call to have an address projection as _embedded

    {
      "_embedded" : {
        "persons" : [ {
           "firstName" : "dfdf",
           "lastName" : "2",
           "addresses" : [ {
            "street" : "tx",
         "state" : "tx",
        "country" : "dfd"
      } ],
      "_embedded" : {
        "addresses" : [ {
          "street" : "tx",
          "_links" : {
            "self" : {
              "href" : "/api/addresses/1{?projection}",
              "templated" : true
            }
          }
        } ]
      },
      "_links" : {
        "self" : {
          "href" : " api/persons/1{?projection}",
          "templated" : true
        },
        "addresses" : {
          "href" : " /api/persons/1/addresses"
        }
        }
       } ]
     }
   }

I dont know if this is expected. This behaviour is causing repeated information when I have a oneToMany relation like order/Comments and have projection on both order and comments and when I access order/1/comments I see the order also embedded for each comments.

Was this ever resolved? I am running into the same problem, especially with the oneToMany problem of repeating — pasquers
– pasquers, Commented Nov 16, 2016 at 17:11

Jaymin Panchal · Accepted Answer · 2017-01-18 10:24:10Z

2

I have a similar issue with spring-data-rest 2.5.6. So I'd like to add this.

If :

an A entity has a @OneToMany relationship to a B entity
the B entity's repository @RepositoryRestResource contains an excerptProjection

Then spring-data-rest will embed the B entity's list in any A entity (in _embedded).

If there is no excerptProjection, the list won't be embedded.

I'd like to be able to choose what I want to be embedded, but at moment, I found no solution to do so.

edited Jan 18, 2017 at 10:24

Jaymin Panchal

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answered Jan 18, 2017 at 10:03

Nicolas Enzweiler

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philDev · Accepted Answer · 2020-05-19 14:56:20Z

For anybody that is looking for the answer to this issue, I actually did find a solution.

Based on the example in Spring-RestBucks you will need to have a custom RepresentationModelProcessor on A entity.

Also consider the official Spring HATEOAS Documentation on RepresentationModelProcessor.

Applying to the above example, you would do:

public class PersonRepresentationProcessor implements RepresentationModelProcessor<EntityModel<Person>> {

  private final EntityLinks entityLinks;

 @Override
 public EntityModel<Person> process(EntityModel<Person> personModel) {
  // create new EntityModel without the embedded collection

  TypedEntityLinks<Person> typedPersonLink = entityLinks.forType(Person::getId);

  EntityModel<Person> newPerson = new EntityModel<>(personModel.getContent(),
                                                    personModel.getLinks());

  // add more links or other modifications
  return newPerson;
 }
}

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