The @DataTableType annotation can mark a method which is able to take a Map<String, String> row from a data table and transform it to a stronger type. The example from here is:

@DataTableType
public Book bookEntryTransformer(Map<String, String> row) {
    return new Book(
        row.get("title"),
        row.get("author"),
        Integer.parseInt(row.get("yearOfPublishing"))
    );
}

How can I take an entire data table rather than a row and transform that to a type which is representing the whole data table?

The use case is I want to process blanks as inheriting the value from the first cell above it which has a value. Example nonsensical illustration:

| title                           | author              | yearOfPublishing |
| To kill a mockingbird           | Harper Lee          | 1960             |
| The catcher in the rye          | J.D. Salinger       | 1951             |
|                                 | F. Scott Fitzgerald | 1925             |

So this data table would be transformed into a new one where the only difference would be the blank cell would have the value The catcher in the rye.

I have written the code to do this – everything works fine when testing but I am coming across problems trying to use it using annotations.