Core components of Roa framework.
If you are new to roa, please go to the documentation of roa framework.
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:
```rust use roa_core::App;
let mut app = App::new(()); app.end(|mut ctx| async move { ctx.resp_mut().write("Hello, World"); Ok(()) }); ```
The following example responds with "Hello World", however, the request flows through
the logging middleware to mark when the request started, then continue
to yield control through the response middleware. When a middleware invokes next.await
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.
```rust use roa_core::App; use std::time::Instant; use log::info;
let mut app = App::new(()); app.gatefn(|ctx, next| async move { let inbound = Instant::now(); next.await?; info!("time elapsed: {} ms", inbound.elapsed().as_millis()); Ok(()) });
app.end(|mut ctx| async move { ctx.resp_mut().write("Hello, World"); Ok(()) }); ```
You can catch or straightly throw an Error returned by next.
```rust use roacore::{App, throw}; use roacore::http::StatusCode;
let mut app = App::new(()); app.gatefn(|ctx, next| async move { // catch if let Err(err) = next.await { // teapot is ok if err.statuscode != StatusCode::IMATEAPOT { return Err(err) } } Ok(()) }); app.gatefn(|ctx, next| async move { next.await?; // just throw unreachable!() }); app.end(|ctx| async move { throw!(StatusCode::IMATEAPOT, "I'm a teapot!") }); ```
App has an errorhandler to handle Error thrown by the top middleware.
This is the errorhandler:
rust
use roa_core::{Context, Error, Result, ErrorKind, State};
pub async fn error_handler<S: State>(mut context: Context<S>, err: Error) -> Result {
context.resp_mut().status = err.status_code;
if err.expose {
context.resp_mut().write(err.message.clone());
}
if err.kind == ErrorKind::ServerError {
Err(err)
} else {
Ok(())
}
}
The Error thrown by this error_handler will be handled by hyper.
Use roa_core::accept to construct a http server.
Please refer to crate 
for more information.