`HttpResponse<'a>` represents an outgoing HTTP message in a Rust web server. A handler constructs the response; the HTTP library converts it to text that the server sends to the client over a TCP stream. The custom type lives in `http/src/httpresponse.rs` and is exported from `http/lib.rs`. section 2.3 section 2.3.2
The custom response has five fields:
- `version`, `status_code`, and `status_text` describe the status line. `Default` sets them to `HTTP/1.1`, `200`, and `OK`. section 2.3.2
- `headers` is an optional map of borrowed strings; `body` is an optional owned `String`. `new(status_code, headers, body)` supplies `Content-Type: text/html` when headers are omitted and selects status text for supported codes. section 2.3.2
- A lifetime annotation ties borrowed field values to the lifetime of the response. Derived `Debug`, `PartialEq`, and `Clone` support inspection, comparison, and cloning. section 2.3.2
Listing 2.15 Code to serialize a Rust struct into an HTTP response message
impl<'a> From<HttpResponse<'a>> for String {
fn from(res: HttpResponse) -> String {
let res1 = res.clone();
format!(
"{} {} {}\r\n{}Content-Length: {}\r\n\r\n{}",
&res1.version(),
&res1.status_code(),
&res1.status_text(),
&res1.headers(),
&res.body.unwrap().len(),
&res1.body()
)
}
}
The `From<HttpResponse> for String` implementation assembles the status line, headers, `Content-Length`, blank line, and body using CRLF separators. It calls `unwrap()` on the body, so this serializer requires a body even though the field is optional. section 2.3.2
Return a missing-page response
`PageNotFoundHandler::handle` constructs `HttpResponse::new("404", None, Self::load_file("404.html"))`. The constructor supplies the default HTML content type and the `Not Found` status text. Tests compare constructed 200 and 404 responses and check the serialized 404 message; run them with `cargo test -p http`. section 2.3.4 section 2.3.2
Other handlers put static pages or JSON data in response bodies and choose a content type appropriate to the returned file. Keep this custom `http`-library type distinct from the `HttpResponse` used in Actix Web handlers: an Actix frontend also acts as a client when it reads a backend service’s JSON response body and deserializes it into `Vec<Tutor>`. section 2.3.4 section 7.7
