Module response 

Available on crate feature set-header only.

Middleware for setting headers on HTTP responses.

This module provides middleware for setting one or more headers on HTTP responses, either with fixed values or values determined dynamically from the response.

Single Header

Use SetResponseHeaderLayer and SetResponseHeader to set a single header. The header value can be a fixed value or computed dynamically using a closure. See crate::set_header::MakeHeaderValue for details.

Example: Fixed Value

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(
        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");

Example: Dynamic Value

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(
        SetResponseHeaderLayer::overriding(
            header::CONTENT_LENGTH,
            |response: &Response<Full<Bytes>>| {
                if let Some(size) = response.body().size_hint().exact() {
                    Some(HeaderValue::from_str(&size.to_string()).unwrap())
                } else {
                    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");

Multiple Headers

Use SetMultipleResponseHeadersLayer and SetMultipleResponseHeader to set multiple headers at once. Each header can have a fixed value or be computed dynamically.

Note: this layer uses boxing (allocation + dynamic dispatch) to support mixed producer types in a single vec. Stacking multiple SetResponseHeaderLayer avoids this at the cost of a more complex composed service type.

Example: Multiple Fixed Values

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


let mut svc = ServiceBuilder::new()
    .layer(
        SetMultipleResponseHeadersLayer::overriding(vec![
            (header::CONTENT_TYPE, HeaderValue::from_static("text/html")).into(),
            (header::CACHE_CONTROL, HeaderValue::from_static("no-cache")).into(),
        ])
    )
    .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");
assert_eq!(response.headers()["cache-control"], "no-cache");

Example: Multiple Dynamic Values

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


let mut svc = ServiceBuilder::new()
    .layer(
        SetMultipleResponseHeadersLayer::overriding(vec![
            (header::CONTENT_LENGTH, |response: &Response<Full<Bytes>>| {
                if let Some(size) = response.body().size_hint().exact() {
                    Some(HeaderValue::from_str(&size.to_string()).unwrap())
                } else {
                    None
                }
            }).into(),
        ])
    )
    .service(render_html);

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

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

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

Modes

• overriding: If a previous value exists for the same header, it is removed and replaced with the new value.
• appending: The new header is always added, preserving any existing values. If previous values exist, the header will have multiple values.
• if_not_present: If a previous value exists for the header, the new value is not inserted.

See SetResponseHeaderLayer, SetResponseHeader, SetMultipleResponseHeadersLayer, and SetMultipleResponseHeader for more details.

Structs

SetMultipleResponseHeader

Middleware that sets multiple headers on the response.

SetMultipleResponseHeadersLayer

Layer that applies SetMultipleResponseHeader which adds multiple response headers.

SetResponseHeader

Middleware that sets a header on the response.

SetResponseHeaderLayer

Layer that applies SetResponseHeader which adds a response header.