Description Thorsten Meinl 2019-08-27 08:06:19 EDT

When trying to insert an array with zero elements into an array column in the database, a NULL value is written instead. This is wrong since NULL is fundamentally different from an empty array. Moreover it triggers bug #537657. The bug seems to be in 

org.eclipse.persistence.mappings.foundation.AbstractCompositeDirectCollectionMapping.writeFromObjectIntoRow(Object, AbstractRecord, AbstractSession, WriteType)

which doesn't handle the case of an empty collection correctly.

Steps to reproduce (with PostgreSQL):

CREATE TABLE foo (
  bar TEXT ARRAY NOT NULL
)

--

@Entity
@Struct(name = "foo")
public class Foo {
  @Column
  @Array(databaseType = "bar")
  List<String> bar = Collections.emptyList();
}

--

EntityManager.persist(new Foo());