Return a hyper::Body of serde:Value

Question

In my situation, my function can only have signature:

pub async fn do_something(mut req: Request<Body>) -> Result<Response<Body>, CustomError> {
  .....
}

I know how to return a body of string in my function as follow:

Ok(Response::new(Body::from("some string".to_string())))

However, something like this does not work with serde::Value; it only worked with strings.

What is the proper way to return a serde::Value while maintaining the same method signature?

score 2 · Accepted Answer · answered Aug 28 '22 at 01:03

2

You can serialize into BytesMut from the bytes crate, then convert into into Body:

use bytes::{BufMut, BytesMut};

let mut buf = BytesMut::new().writer();
serde_json::to_writer(&mut buf, &value)
    .expect("serialization of `serde_json::Value` into `BytesMut` cannot fail");
Ok(Response::new(Body::from(buf.into_inner().freeze())))

If you can afford something less performant, you can serialize into Vec:

Ok(Response::new(Body::from(
    serde_json::to_vec(&value).expect("serialization of `serde_json::Value` into `Vec` cannot fail"),
)))

answered Aug 28 '22 at 01:03

Chayim Friedman

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Why would `to_vec` be less performant? – Caesar Aug 28 '22 at 01:46
1

@Caesar Because it allocates twice: first for the serialization and then [in the conversion to `Bytes`](https://docs.rs/bytes/latest/src/bytes/bytes.rs.html#808-813) (`into_boxed_slice()`). – Chayim Friedman Aug 28 '22 at 02:13
Ah, because it needs to `shink_to_fit`. – Caesar Aug 28 '22 at 02:32

Return a hyper::Body of serde:Value

1 Answers1