Spring data rest and jpa @OneToMany duplicates "_links"

Question

I have a problem with Spring Data Rest being used with Spring Data JPA. I'm using Spring-boot 1.4.4.RELEASE.

Here is my spring-data-rest repository:

public interface ProfileJpaRepository extends JpaRepository<Profile, Long> {
}

Here are my entities (getters and setters not shown for brevity).

Profile.java:

@Entity
@Table(name = "PROFILE")
public class Profile {

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

    private String description;

    // Don't use mappedBy="profile" because attributes are not persisted properly
    @OneToMany(fetch = FetchType.EAGER, cascade = CascadeType.ALL, orphanRemoval = true)
    @JoinColumn(name = "PROFILE_ID")
    private Set<Attribute> attributes;

    ...
}

Attribute.java

@Entity
@Table(name = "ATTRIBUTE")
public class Attribute {

     @Id
     @GeneratedValue(strategy=GenerationType.AUTO)
     @Column(name = "ID")
     private Long id;

     private String uri;

     @ManyToOne(fetch = FetchType.EAGER)
     private Profile profile;

     @ElementCollection(fetch = FetchType.EAGER)
     @CollectionTable(name="ATTRIBUTE_DATAS")
     private List<String> datas = new ArrayList<>();

     public Attribute() {}

     public Attribute(String uri, List<String> datas) {
        this.uri = uri;
        this.datas = datas;
    }

    ...
}

The POST on "http://localhost:8880/profiles" to create the entity:

{
    "description" : "description-value",
    "attributes" : [
        {
            "uri" : "uri-a",
            "datas" : ["uri-a-value"]
        },
        {
            "uri" : "uri-b",
            "datas" : ["uri-b-value"]
        }
    ]
}

And here is the result when I hit http://localhost:8880/profiles :

{
  "_embedded" : {
    "profiles" : [ {
      "description" : "description-value",
      "attributes" : [ {
        "uri" : "uri-a",
        "datas" : [ "uri-a-value" ],
        "_links" : {
          "profile" : {
            "href" : "http://localhost:8880/profiles/1"
          }
        }
      }, {
        "uri" : "uri-b",
        "datas" : [ "uri-b-value" ],
        "_links" : {
          "profile" : {
            "href" : "http://localhost:8880/profiles/1"
          }
        }
      } ],
      "_links" : {
        "self" : {
          "href" : "http://localhost:8880/profiles/1"
        },
        "profile" : {
          "href" : "http://localhost:8880/profiles/1"
        }
      }
    } ]
  },
  "_links" : {
    "self" : {
      "href" : "http://localhost:8880/profiles"
    },
    "profile" : {
      "href" : "http://localhost:8880/profile/profiles"
    }
  },
  "page" : {
    "size" : 20,
    "totalElements" : 1,
    "totalPages" : 1,
    "number" : 0
  }
}

I think there is a problem because the "_links" are specified under every attributes. Rather, I would have expected something like this:

{
  "_embedded" : {
    "profiles" : [ {
      "description" : "description-value",
      "attributes" : [ {
        "uri" : "uri-a",
        "datas" : [ "uri-a-value" ]
      }, {
        "uri" : "uri-b",
        "datas" : [ "uri-b-value" ]
      } ],
      "_links" : {
        "self" : {
          "href" : "http://localhost:8880/profiles/1"
        },
        "profile" : {
          "href" : "http://localhost:8880/profiles/1"
        }
      }
    } ]
  },
  "_links" : {
    "self" : {
      "href" : "http://localhost:8880/profiles"
    },
    "profile" : {
      "href" : "http://localhost:8880/profile/profiles"
    }
  },
  "page" : {
    "size" : 20,
    "totalElements" : 1,
    "totalPages" : 1,
    "number" : 0
  }
}

Note that I have been switching from MongoRepository to JpaRepository, and using MongoRepository, these "_links" were not "duplicated".

Can someone shed some light on this ? Did I misconfigure something on my JPA entities ? Do I need to configure something on the rest repository ?

More information about dependency versions can be found here should you need it, I didn't override these (http://docs.spring.io/spring-boot/docs/1.4.4.RELEASE/reference/html/appendix-dependency-versions.html)

Thanks.

Answer 1

To solve the problem I have been using Projections (more information here: http://docs.spring.io/spring-data/rest/docs/current/reference/html/#projections-excerpts). I wasn't aware of that feature when posting.

I had to annotate my repository and tell it to use my InlineAttributes projection:

import org.springframework.data.rest.core.annotation.RepositoryRestResource;

@RepositoryRestResource(excerptProjection = InlineAttributes.class)
public interface ProfileJpaRepository extends JpaRepository<Profile, Long> {
}

On the Attribute class I had to add the @JsonIgnore annotation:

import com.fasterxml.jackson.annotation.JsonIgnore;

@Entity
@Table(name = "ATTRIBUTE")
public class Attribute {
     ...

     @ManyToOne(fetch = FetchType.EAGER)
     @JsonIgnore
     private Profile profile;

     ...
}

And the InlineAttributes projection class I had to create. I specified the order as it was not the same as before:

import org.springframework.data.rest.core.config.Projection;
import com.fasterxml.jackson.annotation.JsonPropertyOrder;    

@Projection(name = "inlineAttributes", types = { Profile.class })
@JsonPropertyOrder({ "description", "attributes" })
public interface InlineAttributes {

    public String getDescription();
    public Set<Attribute> getAttributes();
}

And then you need to apply the projection when you are calling the rest endpoint:

http://localhost:8880/profiles?projection=inlineAttributes