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actix-web/guide/src/qs_7.md

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# Request & Response
## Response
Builder-like patter is used to construct an instance of `HttpResponse`.
`HttpResponse` provides several method that returns `HttpResponseBuilder` instance,
which is implements various convinience methods that helps build response.
Check [documentation](../actix_web/dev/struct.HttpResponseBuilder.html)
for type description. Methods `.body`, `.finish`, `.json` finalizes response creation,
if this methods get call for the same builder instance, builder will panic.
```rust
# extern crate actix_web;
use actix_web::*;
use actix_web::headers::ContentEncoding;
fn index(req: HttpRequest) -> HttpResponse {
HttpResponse::Ok()
.content_encoding(ContentEncoding::Br)
.content_type("plain/text")
.header("X-Hdr", "sample")
.body("data").unwrap()
}
# fn main() {}
```
## Content encoding
Actix automatically *compress*/*decompress* payload. Following codecs are supported:
* Brotli
* Gzip
* Deflate
* Identity
If request headers contains `Content-Encoding` header, request payload get decompressed
according to header value. Multiple codecs are not supported, i.e: `Content-Encoding: br, gzip`.
Response payload get compressed based on *content_encoding* parameter.
By default `ContentEncoding::Auto` is used. If `ContentEncoding::Auto` is selected
then compression depends on request's `Accept-Encoding` header.
`ContentEncoding::Identity` could be used to disable compression.
If other content encoding is selected the compression is enforced for this codec. For example,
to enable `brotli` response's body compression use `ContentEncoding::Br`:
```rust
# extern crate actix_web;
use actix_web::*;
use actix_web::headers::ContentEncoding;
fn index(req: HttpRequest) -> HttpResponse {
HttpResponse::Ok()
.content_encoding(ContentEncoding::Br)
.body("data").unwrap()
}
# fn main() {}
```
## JSON Response
The `Json` type allows you to respond with well-formed JSON data: simply return a value of
type Json<T> where T is the type of a structure to serialize into *JSON*. The
type `T` must implement the `Serialize` trait from *serde*.
```rust
# extern crate actix_web;
#[macro_use] extern crate serde_derive;
use actix_web::*;
#[derive(Serialize)]
struct MyObj {
name: String,
}
fn index(req: HttpRequest) -> Result<Json<MyObj>> {
Ok(Json(MyObj{name: req.match_info().query("name")?}))
}
fn main() {
Application::new()
.resource(r"/a/{name}", |r| r.method(Method::GET).f(index))
.finish();
}
```