library delete

Delete operation

Delete operation takes a list of book IDs from the request projection, removes them from the backend and reports back errors.

The same map[BookId,BookRecord] is used as a result type, but we will only use it to store errors as values.

Schema

Operation schema is is shown below.

  delete {
    deleteProjection [ required ] ()
    outputProjection [ forbidden ] ()
  }

• delete projection requires keys to be deleted and doesn't accept any BookRecord fields
• output projection forbids keys and doesn't accept any fields either. Output map will only contain keys for failures, with errors as values.

Operation implementation

Logic is simple here: iterate over keys from request projection, ask backend to delete corresponding books, report any "not found" errors.

public class BooksDeleteOperation extends AbstractDeleteOperation {
  BooksDeleteOperation(@NotNull DeleteOperationDeclaration declaration) {
    super(declaration);
  }

  @Override
  protected @NotNull CompletableFuture<BookId_BookRecord_Map.Data> process(
      @NotNull BookId_BookRecord_Map.Builder.Data responseBuilder,
      @NotNull DeleteBooksFieldProjection deleteProjection,
      @NotNull OutputBooksFieldProjection outputProjection) {

    BookId_BookRecord_Map.Builder booksMapBuilder = BookId_BookRecord_Map.create();
    responseBuilder.set(booksMapBuilder);

    for (DeleteBookId_BookRecord_MapKeyProjection keyProjection : deleteProjection.dataProjection().keys()) {
      BookId bookId = keyProjection.value();

      if (!BooksBackend.delete(bookId)) {
        booksMapBuilder.putError(
            bookId,
            new ErrorValue(HttpStatusCode.NOT_FOUND, "Book " + bookId.getVal() + " not found")
        );
      }
    }

    return CompletableFuture.completedFuture(responseBuilder);
  }
}

As usual we have to plug it into BooksResourceFactory:

  @Override
  protected @NotNull DeleteOperation<BookId_BookRecord_Map.Data> constructDeleteOperation(
      @NotNull DeleteOperationDeclaration operationDeclaration) throws ServiceInitializationException {
    return new BooksDeleteOperation(operationDeclaration);
  }

Running

Lets delete books 2 and 5, where book 5 doesn't exist:

curl -s -g -X DELETE "http://localhost:8888/books<[2,5]" | jq

[
  {
    "K": 5,
    "V": {
      "ERROR": 404,
      "message": "Book 5 not found"
    }
  }
]

Nothing is reported for 2 which means a success, and we got a 404 error for 5. Lets check that 2 is actually removed:

curl -s -g "http://localhost:8888/books[1,2,3](title)" | jq

[
  {
    "K": 1,
    "V": {
      "title": "The Gold Bug"
    }
  },
  {
    "K": 2,
    "V": {
      "ERROR": 404,
      "message": "No book with id 2"
    }
  },
  {
    "K": 3,
    "V": {
      "title": "The Adventures of Tom Sawyer"
    }
  }
]

Next section: client