Spring Data Rest - How to change the JSON serialization of a Collection of Abstract Classes

Question

I use Spring Boot v1.2.5 and have the following single table inheritance entities:

@Entity    
@table(name="view_items")
@DiscriminatorColumn(name="type")
public abstract class ViewItem {
   private int position;     
}

@Entity
@DiscriminatorValue(value="table")
public class Table extends ViewItem {}

@Entity
@DiscriminatorValue(value="chart")
public class Chart extends ViewItem {}

public interface ViewItemRepository 
    extends JpaRepository<ViewItem, Integer>{}

And the following association:

@Entity
@Table(name="views")
public class View {

    @OneToMany
    @JoinColumn(name="view_id")
    @OrderBy("position")
    private List<ViewItem> viewItems = new ArrayList<ViewItem>();

    ...
}

Calling GET /views/{id}/viewItems return the collection ordered by subclasse type (some parts have been removed for readability) :

HTTP/1.1 200 OK
Server: Apache-Coyote/1.1
Content-Type: application/hal+json;charset=UTF-8
Transfer-Encoding: chunked

Date: Wed, 23 Sep 2015 07:41:13 GMT

{
  "_embedded" : {        
    "tables" : [ {
      "position": 4,          
        ...
      "_links" : {
        "self" : {
          "href" : "http://localhost:8080/viewItems/3"
        }
      }
    } ],
    "charts" : [ {
      "position": 2,
        ...
      "_links" : {
        "self" : {
          "href" : "http://localhost:8080/viewItems/2"
        }
      }
    } ]
  }

Is there a simple way to change the JSON serialisation having view_items sorted by position like this ? :

{
  "_embedded" : {        
    "2": {
      "type": "chart",
        ...
      "_links" : {
        "self" : {
          "href" : "http://localhost:8080/viewItems/2"
        }
    },
    "4": {
      type: "table",
       ...
      "_links" : {
        "self" : {
          "href" : "http://localhost:8080/viewItems/3"
        }
  }

No luck. The problem is Spring Data Rest serialize into subcollections indexed by type. Maybe subcollections are ordered but it is not the wanted behaviour . — sgt-hartman, Sep 23 '15 at 11:09

score 1 · Accepted Answer · edited May 23 '17 at 12:24

So i found the answer.

Replacing the ViewItems collection mapping type of the View entity from List to Map and adding a read only type field on the ViewItem entity does the trick:

@Entity
@Table(name="views")
public class View {

    @OneToMany
    @JoinColumn(name="view_id")
    @MapKey("position")
    private Map<Integer,ViewItem> viewItems = new HashMap<Integer,ViewItem>();
    ...
}

@Entity    
@table(name="view_items")
@DiscriminatorColumn(name="type")
public abstract class ViewItem {

   @Column(insertable = false, updatable = false)
   public String type;

   ...  
}

EDIT

Months after, and thanks to @aux (see here) here is the solution. A RelProvider class must be implemented, as explained here.

Spring Data Rest - How to change the JSON serialization of a Collection of Abstract Classes

1 Answers1