JSON: Actix Web Documentation

# JSON Extractor

When building APIs, receiving JSON data is a primary requirement. Actix Web uses the web::Json extractor to seamlessly parse incoming JSON payloads into Rust structs.

#Basic Extraction

Simply define a struct that implements Deserialize, and wrap it in web::Json in your handler arguments.

code_blocksrust

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

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

#[post("/users")]
async fn create_user(info: web::Json<CreateUser>) -> HttpResponse {
    HttpResponse::Ok().body(format!("Welcome {}!", info.username))
}

#Payload Configuration

By default, the JSON extractor limits the payload size to prevent Denial of Service (DoS) attacks. You can adjust this limit and customize the error response.

code_blocksrust

use actix_web::{web, App};

App::new().app_data(web::JsonConfig::default().limit(4096))

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Reference Implementation

The following code snippet demonstrates the authoritative pattern for this documentation.

src/main.rs

Edition 2024

1use actix_web::{post, web, App, HttpServer, Responder, HttpResponse};
2use serde::Deserialize;
3 
4#[derive(Deserialize)]
5struct Item {
6    name: String,
7    count: u32,
8}
9 
10#[post("/add")]
11async fn add_item(item: web::Json<Item>) -> impl Responder {
12    HttpResponse::Ok().body(format!("Added {} x {}", item.count, item.name))
13}
14 
15#[actix_web::main]
16async fn main() -> std::io::Result<()> {
17    HttpServer::new(|| App::new().service(add_item))
18        .bind(("127.0.0.1", 8080))?
19        .run()
20        .await
21}

JSON

#Basic Extraction

#Payload Configuration

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Reference Implementation

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