added error_handling example

Cargo.toml

@@ -8,6 +8,7 @@ members = [
   "cookie-auth-full",
   "cookie-session",
   "diesel",
+  "error_handling",
   "form",
   "hello-world",
   "http-proxy",

error_handling/.gitignore

@@ -0,0 +1,2 @@
+/target
+**/*.rs.bk

error_handling/Cargo.toml

@@ -0,0 +1,12 @@
+[package]
+name = "error_handling"
+version = "0.1.0"
+authors = ["dowwie <dkcdkg@gmail.com>"]
+
+[dependencies]
+actix = "0.7.3"
+actix-web = "0.7.3"
+failure = "0.1.2"
+futures = "0.1.23"
+rand = "0.5.4"
+env_logger = "0.5.12"

error_handling/README.md

@@ -0,0 +1 @@
+This project illustrates custom error propagation through futures in actix-web

error_handling/src/main.rs

@@ -0,0 +1,139 @@
+/*
+The goal of this example is to show how to propagate a custom error type, derived
+from the Fail trait, to a web handler that will evaluate the type of error that
+was raised and return an appropriate HTTPResponse.
+
+This example uses a 50/50 chance of returning 200 Ok, otherwise one of four possible
+http errors will be chosen, each with an equal chance of being selected: 
+    1. 403 Forbidden
+    2. 401 Unauthorized
+    3. 500 InternalServerError
+    4. 400 BadRequest
+
+*/
+
+
+extern crate actix;
+extern crate actix_web;
+extern crate env_logger;
+#[macro_use] extern crate failure;
+extern crate futures;
+extern crate rand;
+
+
+use actix_web::{
+    http::Method, server, App, AsyncResponder, Error as ActixWebError,
+    HttpResponse, HttpRequest
+};
+use failure::Error as FailureError;  // naming it clearly for illustration purposes
+use futures::{
+    future::{
+        ok as fut_ok, 
+        err as fut_err
+    },
+    Future
+};
+use rand::{thread_rng, Rng, distributions::{Distribution, Standard}};
+
+
+
+#[derive(Fail, Debug)]
+pub enum CustomError {
+    #[fail(display = "Custom Error 1")]
+    CustomOne,
+    #[fail(display = "Custom Error 2")]
+    CustomTwo,
+    #[fail(display = "Custom Error 3")]
+    CustomThree,
+    #[fail(display = "Custom Error 4")]
+    CustomFour
+}
+
+
+impl Distribution<CustomError> for Standard {
+    fn sample<R: Rng + ?Sized>(&self, rng: &mut R) -> CustomError {
+        match rng.gen_range(0, 4) {
+            0 => CustomError::CustomOne,
+            1 => CustomError::CustomTwo,
+            2 => CustomError::CustomThree,
+            _ => CustomError::CustomFour
+        }
+    }
+}
+
+/*
+impl ResponseError for CustomError {
+    fn error_response(&self) -> HttpResponse {
+        HttpResponse::new(StatusCode::INTERNAL_SERVER_ERROR)
+    }
+}
+*/
+
+
+/// randomly returns either () or one of the 4 CustomError variants
+//fn do_something_random() -> impl Future<Item = Result<(), FailureError>,
+//                                        Error = ActixWebError> {
+fn do_something_random() -> impl Future<Item = (), Error = CustomError> {
+    let mut rng = thread_rng();
+
+    // 20% chance that () will be returned by this function
+    if rng.gen_bool(2.0/10.0) {
+        return fut_ok(())
+    }
+
+    let err: CustomError = rand::random();
+    return fut_err(err)
+}
+
+
+fn do_something(_req: HttpRequest)
+                -> impl Future<Item = HttpResponse, Error = ActixWebError> {
+
+    do_something_random()
+    .then(|result| match result {
+        Ok(_) => Ok(HttpResponse::Ok()
+                    .body("Nothing interesting happened.  Try again.")),
+
+        Err(err) => match err {
+              CustomError::CustomOne => {
+                  println!("do some stuff related to CustomOne error");
+                  Ok(HttpResponse::Forbidden().finish())
+              },
+
+              CustomError::CustomTwo => {
+                  println!("do some stuff related to CustomTwo error");
+                  Ok(HttpResponse::Unauthorized().finish())
+              },
+
+              CustomError::CustomThree => {
+                  println!("do some stuff related to CustomThree error");
+                  Ok(HttpResponse::InternalServerError().finish())
+              },
+             
+              _ => {
+                  println!("do some stuff related to CustomFour error");
+                  Ok(HttpResponse::BadRequest().finish())
+              }
+        }
+    })
+    .responder()
+}
+
+
+fn main() {
+    ::std::env::set_var("RUST_LOG", "actix_web=info");
+    env_logger::init();
+    let sys = actix::System::new("error_handling_example");
+
+    server::new(move || {
+        App::new()
+            .resource("/something", |r|
+                      r.method(Method::GET)
+                       .with_async(do_something))
+    }).bind("127.0.0.1:8088")
+        .unwrap()
+        .start();
+
+    println!("Started http server: 127.0.0.1:8088");
+    let _ = sys.run();
+}