Support arrays/collections mapping

[stIncMale]

This PR introduces tests for null values, including tests for empty @Embeddable values (ones that have null as the value of each of the persistence attributes), and the commit c4986fa has hacked-in implementation of null support to allow running those tests. You may identify such tests by searching for @Disabled.

HIBERNATE-58

[stIncMale]

There is likely a bug in Hibernate ORM causing this behavior.

[NathanQingyangXu]

I digged a little bit. The root cause is BasicTypeRegistry registries both byte[] and Byte[] with value of the latter. If we use legacy as the hibernate.type.wrapper_array_handling property, the issue would be gone.

Not 100% sure but it seems this is as expected. We might need to know all the details of the new property introduced since 6.2 to fully grasp.

[NathanQingyangXu]

The org.hibernate.mapping.Property#isValid() provides some helpful context as below (https://github.com/hibernate/hibernate-orm/blob/main/hibernate-core/src/main/java/org/hibernate/mapping/Property.java#L293):

So from my understanding, if hibernate.type.wrapper_array_handling property is set to allow, Byte[] instead of byte[] is supposed to be used; otherwise legacy property might make more sense.

Still kind of defective but mixture of byte[] and Byte[] seems inconsistent with the allow configuration as well.

[stIncMale]

from my understanding, if hibernate.type.wrapper_array_handling property is set to allow, Byte[] instead of byte[] is supposed to be used

I did not find anything in the documentation, or even in the error message you linked, that points to such a limitation.

[NathanQingyangXu]

I think you can ask Christian on Zulip directly. Again he is the developer for this feature.

[stIncMale]

@NathanQingyangXu, thank you for asking this question: https://hibernate.zulipchat.com/#narrow/channel/132094-hibernate-orm-dev/topic/hibernate.2Etype.2Ewrapper_array_handling.20setting.20issue/with/525325554.

[NathanQingyangXu]

Christian created a Hibernate ORM ticket at https://hibernate.atlassian.net/browse/HHH-19573

[NathanQingyangXu]

The bug has been fixed since v6.6.19. FYI.

[NathanQingyangXu]

From my side, no LGTM blocker for me.
There is an interesting discussion regarding struct fetching robustness issue, but it could be done later, if the issue is valid.

[NathanQingyangXu]

I should have raised this concern in last PR. I think we should create some testing case to showcase that Struct's field annotated with customized @Column should take effect. I tested it on main branch and found it works as expected, but it seems not to hurt to provide an integration testing case to protect us. An example testing case is like below:

@SessionFactory(exportSchema = false)
@DomainModel(
        annotatedClasses = {
                TestStructWithCustomizedColumnName.Book.class,
                TestStructWithCustomizedColumnName.Author.class
        })
@ExtendWith(MongoExtension.class)
class TestStructWithCustomizedColumnName {

    @InjectMongoCollection("books")
    private static MongoCollection<BsonDocument> mongoCollection;

    @Test
    void testFieldNameIsCustomized(SessionFactoryScope scope) {
        var book = new Book();
        book.id = 1;
        book.title = "Effective Java";
        var author = new Author();
        author.firstName = "Joshua";
        author.lastName = "Bloch";
        book.author = author;
        scope.inTransaction(session -> session.persist(book));
        assertThat(mongoCollection.find()).containsExactly(BsonDocument.parse(
                """
                {
                  "_id": 1,
                  "title": "Effective Java",
                  "author": {
                    "first_name": "Joshua",
                    "last_name": "Bloch"
                  }
                }
                """
        ));
    }

    @Entity(name = "Book")
    @Table(name = "books")
    static class Book {
        @Id
        int id;
        String title;
        Author author;
    }

    @Embeddable
    @Struct(name = "Author")
    static class Author {
        @Column(name = "first_name")
        String firstName;
        @Column(name = "last_name")
        String lastName;

    }
}

[NathanQingyangXu]

there are still cases that var is not used consistently, though I am perfectly fine with it.