[−][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::core::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(|ctx| async move { ctx.write_text("Hello, World").await }); 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::core::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().await.must_get("x-response-time")?.to_owned(); info!("{} {} - {}", ctx.method().await, ctx.uri().await, rt); Ok(()) }); // x-response-time app.gate_fn(|ctx, next| async move { let start = Instant::now(); next().await?; let ms = start.elapsed().as_millis(); ctx.resp_mut().await.insert("x-response-time", format!("{}ms", ms))?; Ok(()) }); // response app.end(|ctx| async move { ctx.write_text("Hello, World").await }); 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::core::{App, throw, 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, Model, ErrorKind}; pub async fn error_handler<M: Model>(context: Context<M>, err: Error) -> Result { // set status code to err.status_code. context.resp_mut().await.status = err.status_code; if err.expose { // write err.message to response body if err.expose. context.resp_mut().await.write_str(&err.message); } 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::core::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").await?.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::core::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").await?.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_core as core; |
Modules
body | The body module of roa.
This module provides a context extension |
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 |
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 |
router | The router module of roa.
This module provides a middleware |