tower_http::set_header

Module response

Source
Available on crate feature set-header only.
Expand description

Set a header on the response.

The header value to be set may be provided as a fixed value when the middleware is constructed, or determined dynamically based on the response by a closure. See the MakeHeaderValue trait for details.

§Example

Setting a header from a fixed value provided when the middleware is constructed:

use http::{Request, Response, header::{self, HeaderValue}};
use tower::{Service, ServiceExt, ServiceBuilder};
use tower_http::set_header::SetResponseHeaderLayer;
use http_body_util::Full;
use bytes::Bytes;

let mut svc = ServiceBuilder::new()
    .layer(
        // Layer that sets `Content-Type: text/html` on responses.
        //
        // `if_not_present` will only insert the header if it does not already
        // have a value.
        SetResponseHeaderLayer::if_not_present(
            header::CONTENT_TYPE,
            HeaderValue::from_static("text/html"),
        )
    )
    .service(render_html);

let request = Request::new(Full::default());

let response = svc.ready().await?.call(request).await?;

assert_eq!(response.headers()["content-type"], "text/html");

Setting a header based on a value determined dynamically from the response:

use http::{Request, Response, header::{self, HeaderValue}};
use tower::{Service, ServiceExt, ServiceBuilder};
use tower_http::set_header::SetResponseHeaderLayer;
use bytes::Bytes;
use http_body_util::Full;
use http_body::Body as _; // for `Body::size_hint`

let mut svc = ServiceBuilder::new()
    .layer(
        // Layer that sets `Content-Length` if the body has a known size.
        // Bodies with streaming responses wont have a known size.
        //
        // `overriding` will insert the header and override any previous values it
        // may have.
        SetResponseHeaderLayer::overriding(
            header::CONTENT_LENGTH,
            |response: &Response<Full<Bytes>>| {
                if let Some(size) = response.body().size_hint().exact() {
                    // If the response body has a known size, returning `Some` will
                    // set the `Content-Length` header to that value.
                    Some(HeaderValue::from_str(&size.to_string()).unwrap())
                } else {
                    // If the response body doesn't have a known size, return `None`
                    // to skip setting the header on this response.
                    None
                }
            }
        )
    )
    .service(render_html);

let request = Request::new(Full::default());

let response = svc.ready().await?.call(request).await?;

assert_eq!(response.headers()["content-length"], "10");

Structs§