examples/json/json-error/src/main.rs

//! This example is meant to show how to automatically generate a json error response when something goes wrong.

use std::{fmt, io};

use actix_web::{App, HttpResponse, HttpServer, ResponseError, http::StatusCode, web};
use serde::Serialize;

#[derive(Debug, Serialize)]
struct Error {
    msg: String,
    status: u16,
}

impl fmt::Display for Error {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        write!(f, "{}", serde_json::to_string_pretty(self).unwrap())
    }
}

impl ResponseError for Error {
    // builds the actual response to send back when an error occurs
    fn error_response(&self) -> HttpResponse {
        let err_json = serde_json::json!({ "error": self.msg });
        HttpResponse::build(StatusCode::from_u16(self.status).unwrap()).json(err_json)
    }
}

async fn index() -> Result<HttpResponse, Error> {
    Err(Error {
        msg: "an example error message".to_owned(),
        status: 400,
    })
}

#[actix_web::main]
async fn main() -> io::Result<()> {
    env_logger::init_from_env(env_logger::Env::new().default_filter_or("info"));

    log::info!("starting HTTP server at http://localhost:8080");

    HttpServer::new(|| App::new().service(web::resource("/").route(web::get().to(index))))
        .workers(2)
        .bind(("127.0.0.1", 8080))?
        .run()
        .await
}