Zip Mono with 2 other Monos-CodePudding

I need to get information about a Book, Author and Publisher.

The Book contains information about the Author and Publisher.

I'm getting the BookInfo using the following method:

bookService.getBook( tenantId, bookId )
           .zipWhen( book -> authorService.getAuthor( tenantId, book.getAuthorId() ) )
           .zipWhen( tuple -> publisherService.getPublisher( tenantId, tupple.getT1().getPublisherId() ) )
           .map( tuple -> new BookInfo( tupple.getT1().getT1(), tupple.getT1().getT2(), tupple.getT2() ) );

I'm using zipWhen to share the Book to the other method calls but as you can see it's a mess since at the end I get a tuple with another tuple inside.

Is there a better way of doing this?

Would even be possible to call the authorService and the publisherService in parallel?

CodePudding user response：

You can use the zip static operator which may take more than one source publisher (it would be the Author and Publisher) and combine the results in a Tuple2 then map the result in-place to a BookInfo object.

bookService.getBook(tenantId, bookId)
       .flatMap(book -> Mono.zip(authorService.getAuthor(tenantId, book.getAuthorId()), publisherService.getPublisher(tenantId, book.getPublisherId()))
               .map(tuple -> new BookInfo(book, tuple.getT1(), tupple.getT2()))
       );

You may optionally make both authService and publisherServie subscribeOn a different scheduler to have results computed in parallel:

CodePudding user response：

You can use Mono.zip inside flatMap()

 getBook(tenantId, bookId).flatMap(book ->
                Mono.zip(
                        Mono.just(book),
                        getAuthor(tenantId, book.getAuthorId()),
                        getPublisher(tenantId, book.getPublisherId())
                )
        ).map(tuple -> {
            tuple.getT1(); // book
            tuple.getT2(); // author
            tuple.getT3(); // publisher
            // ... build BookInfo here and return
        })

flatMap() operator is async by it's nature