desrialize json when using curl

[videni]

example are copied from offical web site

#[macro_use]
extern crate serde_derive;
#[macro_use]
extern crate serde_json;


use actix_web::{error, web, App, HttpResponse, HttpServer, Responder};
use serde::Deserialize;

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

/// deserialize `Info` from request's body, max payload size is 4kb
async fn index(info: web::Json<Info>) -> impl Responder {
    format!("Welcome {}!", info.username)
}

#[actix_web::main]
async fn main() -> std::io::Result<()> {
    HttpServer::new(|| {
        // let json_config = web::JsonConfig::default()
        //     .limit(4096)
        //     .error_handler(|err, _req| {
        //         // create custom error response
        //         error::InternalError::from_response(err, HttpResponse::Conflict().finish()).into()
        //     });

        App::new().service(
            web::resource("/")
                // change json extractor configuration
                // .app_data(json_config)
                .route(web::post().to(index)),
        )
    })
    .bind("127.0.0.1:8080")?
    .run()
    .await
}

curl --data '{"username": "abc12312313"}' -v http://127.0.0.1:8080

*   Trying 127.0.0.1...
* TCP_NODELAY set
* Connected to 127.0.0.1 (127.0.0.1) port 8080 (#0)
> POST / HTTP/1.1
> Host: 127.0.0.1:8080
> User-Agent: curl/7.64.1
> Accept: */*
> Content-Length: 27
> Content-Type: application/x-www-form-urlencoded
>
* upload completely sent off: 27 out of 27 bytes
< HTTP/1.1 400 Bad Request
< content-length: 0
< date: Fri, 09 Apr 2021 10:20:26 GMT
<
* Connection #0 to host 127.0.0.1 left intact
* Closing connection 0

[robjtede]

the content type must be set correctly for json extractor to work
curl --data '{"username": "abc12312313"}' --header 'Content-Type: application/json' -v http://127.0.0.1:8080