JSON Request

There are several options for json body deserialization.

The first option is to use Json extractor. First, you define a handler function that accepts Json<T> as a parameter, then, you use the .to() method for registering this handler. It is also possible to accept arbitrary valid json object by using serde_json::Value as a type T.

First example of JSON Request depends on serde:

[dependencies]
serde = { version = "1.0", features = ["derive"] }

Second example of JSON Request depends on serde and serde_json and futures:

[dependencies]
serde = { version = "1.0", features = ["derive"] }
serde_json = "1"
futures = "0.3"

If you want to add default value for a field, refer to serde's documentation.

use actix_web::{web, App, HttpServer, Result};
use serde::Deserialize;

#[derive(Deserialize)]
struct Info {
    username: String,
}

/// extract `Info` using serde
async fn index(info: web::Json<Info>) -> Result<String> {
    Ok(format!("Welcome {}!", info.username))
}

#[actix_web::main]
async fn main() -> std::io::Result<()> {
    HttpServer::new(|| App::new().route("/", web::post().to(index)))
        .bind(("127.0.0.1", 8080))?
        .run()
        .await
}

You may also manually load the payload into memory and then deserialize it.

In the following example, we will deserialize a MyObj struct. We need to load the request body first and then deserialize the json into an object.

use actix_web::{error, post, web, App, Error, HttpResponse};
use futures::StreamExt;
use serde::{Deserialize, Serialize};

#[derive(Serialize, Deserialize)]
struct MyObj {
    name: String,
    number: i32,
}

const MAX_SIZE: usize = 262_144; // max payload size is 256k

#[post("/")]
async fn index_manual(mut payload: web::Payload) -> Result<HttpResponse, Error> {
    // payload is a stream of Bytes objects
    let mut body = web::BytesMut::new();
    while let Some(chunk) = payload.next().await {
        let chunk = chunk?;
        // limit max size of in-memory payload
        if (body.len() + chunk.len()) > MAX_SIZE {
            return Err(error::ErrorBadRequest("overflow"));
        }
        body.extend_from_slice(&chunk);
    }

    // body is loaded, now we can deserialize serde-json
    let obj = serde_json::from_slice::<MyObj>(&body)?;
    Ok(HttpResponse::Ok().json(obj)) // <- send response
}

A complete example for both options is available in examples directory.

Content Encoding

Actix Web automatically decompresses payloads. The following codecs are supported:

• Brotli
• Gzip
• Deflate
• Zstd

If request headers contain a Content-Encoding header, the request payload is decompressed according to the header value. Multiple codecs are not supported, i.e: Content-Encoding: br, gzip.

Chunked transfer encoding

Actix automatically decodes chunked encoding. The web::Payload extractor already contains the decoded byte stream. If the request payload is compressed with one of the supported compression codecs (br, gzip, deflate), then the byte stream is decompressed.

Multipart body

Actix Web provides multipart stream support with an external crate, actix-multipart.

A full example is available in the examples directory.

Urlencoded body

Actix Web provides support for application/x-www-form-urlencoded encoded bodies with the web::Form extractor which resolves to the deserialized instance. The type of the instance must implement the Deserialize trait from serde.

The UrlEncoded future can resolve into an error in several cases:

• content type is not application/x-www-form-urlencoded
• transfer encoding is chunked.
• content-length is greater than 256k
• payload terminates with error.

use actix_web::{post, web, HttpResponse};
use serde::Deserialize;

#[derive(Deserialize)]
struct FormData {
    username: String,
}

#[post("/")]
async fn index(form: web::Form<FormData>) -> HttpResponse {
    HttpResponse::Ok().body(format!("username: {}", form.username))
}

Streaming request

HttpRequest is a stream of Bytes objects. It can be used to read the request body payload.

In the following example, we read and print the request payload chunk by chunk:

use actix_web::{get, web, Error, HttpResponse};
use futures::StreamExt;

#[get("/")]
async fn index(mut body: web::Payload) -> Result<HttpResponse, Error> {
    let mut bytes = web::BytesMut::new();
    while let Some(item) = body.next().await {
        let item = item?;
        println!("Chunk: {:?}", &item);
        bytes.extend_from_slice(&item);
    }

    Ok(HttpResponse::Ok().finish())
}