fastexcel VS Vert.x

I'm using fastexcel to create the excel file, and I'm flushing it to the OutputStream after every row is written. Right now, I am using a FileOutputStream to write to disk. When the excel file is done being generated, I read it back in using InputStreamResource and stream the response. My thought process is that a ByteArrayOutputStream keeps everything in memory even if I'm flushing the excel file after every row, so I used the FileOutputStream. Does my logic track here? Or am I unnecessarily slowing things down with expensive filesystem IO?

fastexcel the fastest xlsx generation library

I would use some library like for example this one. So you collect all the data you want to store in a list or map, and iterate over it, then add them to the excel like shown in the documentation of the library (should always be the same way more or less for any library)

I've only had memory problems with apache poi. I only use https://github.com/dhatim/fastexcel now

https://vertx.io/

It's actively maintained with full time developers, performant, supports Kotlin out of the box, and has more features?

Hibernate Reactive integrates with Vert.x, but an extension allows to bridge to Project Reactor if wanted

Have you looked at Vert.x?

Explicitly so:

I really like Eclipse Vert.x... As both an Erlang dev and Java dev, it's a great synergy and soon to have support for Virtual Threads similar to BEAM.

There are many lean, popular, non-magical libraries in Java land. (https://quarkus.io/, https://vertx.io/, etc). Spring is a monster 😱. Its like comparing Kubernetes (written in Go) with some lean framework in another lang.

Eclipse Vert.x - Add amazing Async to any Java stack

Vert.X example: https://github.com/eclipse-vertx/vert.x/blob/master/src/main/java/examples/EventBusExamples.java#L106 (couldn't even find docs)

In fact, it builds on top of proven standards such as Eclipse MicroProfile or frameworks such as Vert.x or JAX‑RS.