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
– sgt-hartman, Commented Sep 23, 2015 at 11:09

Community · Accepted Answer · 2017-05-23 12:24:24Z

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.

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