[−][src]Crate roa
Introduction
Roa is an async web framework inspired by koajs, lightweight but powerful.
Application
A Roa application is a structure containing a middleware group which composes and executes middleware functions in a stack-like manner.
The obligatory hello world application:
use roa::App; use roa::preload::*; use log::info; use std::error::Error as StdError; #[async_std::main] async fn main() -> Result<(), Box<dyn StdError>> { let mut app = App::new(()); app.end(|mut ctx| async move { ctx.write_text("Hello, World") }); app.listen("127.0.0.1:8000", |addr| { info!("Server is listening on {}", addr) })? .await?; Ok(()) }
Cascading
Like koajs, middleware suspends and passes control to "downstream" by invoking next.await
.
Then control flows back "upstream" when next.await
returns.
The following example responds with "Hello World", however first the request flows through the x-response-time and logging middleware to mark when the request started, then continue to yield control through the response middleware. When a middleware invokes next the function suspends and passes control to the next middleware defined. After there are no more middleware to execute downstream, the stack will unwind and each middleware is resumed to perform its upstream behaviour.
use roa::App; use roa::preload::*; use log::info; use std::error::Error as StdError; use std::time::Instant; #[async_std::main] async fn main() -> Result<(), Box<dyn StdError>> { let mut app = App::new(()); // logger app.gate_fn(|ctx, next| async move { next.await?; let rt = ctx.resp().must_get("x-response-time")?; info!("{} {} - {}", ctx.method(), ctx.uri(), rt); Ok(()) }); // x-response-time app.gate_fn(|mut ctx, next| async move { let start = Instant::now(); next.await?; let ms = start.elapsed().as_millis(); ctx.resp_mut().insert("x-response-time", format!("{}ms", ms))?; Ok(()) }); // response app.end(|mut ctx| async move { ctx.write_text("Hello, World") }); app.listen("127.0.0.1:8000", |addr| { info!("Server is listening on {}", addr) })? .await?; Ok(()) }
Error Handling
You can catch or straightly throw an error returned by next.
use roa::{App, throw}; use roa::preload::*; use roa::http::StatusCode; use async_std::task::spawn; use log::info; #[async_std::main] async fn main() -> Result<(), Box<dyn std::error::Error>> { App::new(()) .gate_fn(|ctx, next| async move { // catch if let Err(err) = next.await { // teapot is ok if err.status_code != StatusCode::IM_A_TEAPOT { return Err(err) } } Ok(()) }) .gate_fn(|ctx, next| async move { next.await?; // just throw unreachable!() }) .end(|_ctx| async move { throw!(StatusCode::IM_A_TEAPOT, "I'm a teapot!") }) .listen("127.0.0.1:8000", |addr| { info!("Server is listening on {}", addr) })? .await?; Ok(()) }
error_handler
App has an error_handler to handle error thrown by the top middleware. This is the error_handler:
use roa_core::{Context, Error, Result, State, ErrorKind}; pub async fn error_handler<S: State>(mut context: Context<S>, err: Error) -> Result { // set status code to err.status_code. context.resp_mut().status = err.status_code; if err.expose { // write err.message to response body if err.expose. context.resp_mut().write(err.message.clone()); } if err.kind == ErrorKind::ServerError { // thrown to hyper Err(err) } else { // caught Ok(()) } }
The error thrown by this error_handler will be handled by hyper.
Router.
Roa provides a configurable and nestable router.
use roa::preload::*; use roa::router::Router; use roa::App; use async_std::task::spawn; use log::info; #[async_std::main] async fn main() -> Result<(), Box<dyn std::error::Error>> { let mut router = Router::<()>::new(); // get dynamic "/:id" router.get("/:id", |ctx| async move { let id: u64 = ctx.must_param("id")?.parse()?; // do something Ok(()) }); App::new(()) // route with prefix "/user" .gate(router.routes("/user")?) .listen("127.0.0.1:8000", |addr| { info!("Server is listening on {}", addr) })? .await?; // get "/user/1", then id == 1. Ok(()) }
Query
Roa provides a middleware query_parser
.
use roa::preload::*; use roa::query::query_parser; use roa::App; use async_std::task::spawn; use log::info; #[async_std::main] async fn main() -> Result<(), Box<dyn std::error::Error>> { App::new(()) .gate(query_parser) .end( |ctx| async move { let id: u64 = ctx.must_query("id")?.parse()?; Ok(()) }) .listen("127.0.0.1:8080", |addr| { info!("Server is listening on {}", addr) })? .await?; // request "/?id=1", then id == 1. Ok(()) }
Other modules
- body: dealing with body more conviniently.
- compress: supports transparent content compression.
- cors: CORS support.
- forward: "X-Forwarded-*" parser.
- header: dealing with headers more conviniently.
- jwt: json web token support.
- logger: a logger middleware.
Re-exports
pub use roa_body as body; |
pub use roa_router as router; |
pub use roa_tcp as tcp; |
pub use roa_tls as tls; |
pub use roa_websocket as websocket; |
Modules
compress | The compress module of roa.
This module provides a middleware |
cookie | The cookie module of roa.
This module provides a middleware |
cors | The cors module of roa.
This module provides a middleware |
forward | The forward module of roa.
This module provides a context extension |
header | The header module of roa.
This module provides a Request/Response extension |
http | A general purpose library of common HTTP types |
jwt | The jwt module of roa.
This module provides middlewares |
logger | The logger module of roa.
This module provides a middleware |
preload | Reexport all extensional traits. |
query | The query module of roa.
This module provides a middleware |
Macros
throw | Throw an |
Structs
AddrStream | A transport returned yieled by |
App | The Application of roa. |
Context | A structure to share request, response and other data between middlewares. |
Error | The |
Executor | A type implementing hyper::rt::Executor |
JoinHandle | A handle that awaits the result of a task. |
Request | Http request type of roa. |
Response | Http response type of roa. |
Server | A listening HTTP server that accepts connections in both HTTP1 and HTTP2 by default. |
SyncContext | Sync parts of Context. |
Variable | A wrapper of Arc |
Enums
Body | The body of response. |
ErrorKind | Kind of Error. |
Traits
Accept | Asynchronously accept incoming connections. |
Middleware | Middleware |
Spawn | Executor constraint. |
State | The |
Functions
join | Join two middleware. |
join_all | Join all middlewares in a vector. |
last | The last. |
Type Definitions
BlockingObj | Blocking task Object |
FutureObj | Future Object |
Next | Type of the second parameter in a middleware. |
Result | Type alias for |
ResultFuture | Type alias for |
Attribute Macros
async_trait |