OrderColumn annotations are not supported on Set attributes

In OpenJPA, an entity class with an OrderColumn annotation on an attribute of type java.util.Set is allowed even though the Set interface does not guarantee order. EclipseLink is stricter and allows an OrderColumn annotation only on attributes of type java.util.List.

This rule flags @OrderColumn annotations found on attributes that implement the following interfaces:

java.util.Set<E>
java.util.SortedSet<E>
java.util.NavigableSet<E>

Although SortedSet, a subinterface of Set, provides ordering with its Comparable interface, it is not supported by EclipseLink.

You can solve this issue in two ways depending on the importance of retaining order of the collection.

If order is important, change the type of the attribute from a Set collection to a List collection.
If order is not important, remove the OrderColumn annotation.

In the following entity class, both OrderColumn annotations are flagged by this rule.

import java.util.HashSet;
import java.util.Set;

import javax.persistence.ElementCollection;
import javax.persistence.Entity;
import javax.persistence.Id;
import javax.persistence.OrderColumn;
import javax.persistence.OneToMany;

@Entity
public class OrderColumnExampleEntity {
    @Id
    private int id;
 
    @ElementCollection
    @OrderColumn
    private Set<String> setOfStrings = new HashSet<String>();
    
    @OneToMany
    @OrderColumn
    private Set<RelatedObject> setOfObjects = new HashSet<RelatedObject>();
}

The following example shows implementing both possible solutions.

import java.util.ArrayList;
import java.util.HashSet;
import java.util.List;
import java.util.Set;

import javax.persistence.ElementCollection;
import javax.persistence.Entity;
import javax.persistence.Id;
import javax.persistence.OrderColumn;
import javax.persistence.OneToMany;

@Entity
public class OrderColumnExampleEntity {
    @Id
    private int id;
 
    // Remove the OrderColumn annotation
    @ElementCollection
    private Set<String> setOfStrings = new HashSet<String>();
    
    // Change the collection to a List
    @OneToMany
    @OrderColumn
    private List<RelatedObject> setOfObjects = new ArrayList<RelatedObject>();
}

For information about this issue and other OpenJPA to EclipseLink migration issues, see the OpenJPA to EclipseLink JPA Migration: Mappings guide.