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55 lines
2.4 KiB
Markdown
55 lines
2.4 KiB
Markdown
---
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title: Responses
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---
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import CodeBlock from "@site/src/components/code_block.js";
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# Response
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A builder-like pattern is used to construct an instance of `HttpResponse`. `HttpResponse` provides several methods that return a `HttpResponseBuilder` instance, which implements various convenience methods for building responses.
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> Check the [documentation][responsebuilder] for type descriptions.
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The methods `.body`, `.finish`, and `.json` finalize response creation and return a constructed _HttpResponse_ instance. If this methods is called on the same builder instance multiple times, the builder will panic.
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<CodeBlock example="responses" file="main.rs" section="builder" />
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## JSON Response
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The `Json` type allows 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_.
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For the following example to work, you need to add `serde` to your dependencies in `Cargo.toml`:
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```toml
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[dependencies]
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serde = { version = "1.0", features = ["derive"] }
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```
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<CodeBlock example="responses" file="json_resp.rs" section="json-resp" />
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Using the `Json` type this way instead of calling the `.json` method on a `HttpResponse` makes it immediately clear that the function returns JSON and not any other type of response.
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## Content encoding
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Actix Web can automatically _compress_ payloads with the [_Compress middleware_][compressmidddleware]. The following codecs are supported:
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- Brotli
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- Gzip
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- Deflate
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- Identity
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A response's `Content-Encoding` header defaults to `ContentEncoding::Auto`, which performs automatic content compression negotiation based on the request's `Accept-Encoding` header.
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<CodeBlock example="responses" file="auto.rs" section="auto" />
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Explicitly disable content compression on a handler by setting `Content-Encoding` to an `Identity` value:
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<CodeBlock example="responses" file="identity.rs" section="identity" />
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When dealing with an already compressed body (for example, when serving pre-compressed assets), set the `Content-Encoding` header on the response manually to bypass the middleware:
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<CodeBlock example="responses" file="identity_two.rs" section="identity-two" />
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[responsebuilder]: https://docs.rs/actix-web/4/actix_web/struct.HttpResponseBuilder.html
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[compressmidddleware]: https://docs.rs/actix-web/4/actix_web/middleware/struct.Compress.html
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