[−][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, Context};
use roa::preload::*;
use log::info;
use std::error::Error as StdError;

async fn end(ctx: &mut Context<()>) -> roa::Result {
    ctx.write_text("Hello, World");
    Ok(())
}

#[async_std::main]
async fn main() -> Result<(), Box<dyn StdError>> {
    let app = App::new(()).end(end);
    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, Context, Next};
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 app = App::new(())
        .gate(logger)
        .gate(x_response_time)
        .end(response);
    app.listen("127.0.0.1:8000", |addr| {
        info!("Server is listening on {}", addr)
    })?
    .await?;
    Ok(())
}

async fn logger(ctx: &mut Context<()>, next: Next<'_>) -> roa::Result {
    next.await?;
    let rt = ctx.resp.must_get("x-response-time")?;
    info!("{} {} - {}", ctx.method(), ctx.uri(), rt);
    Ok(())
}

async fn x_response_time(ctx: &mut Context<()>, next: Next<'_>) -> roa::Result {
    let start = Instant::now();
    next.await?;
    let ms = start.elapsed().as_millis();
    ctx.resp.insert("x-response-time", format!("{}ms", ms))?;
    Ok(())
}

async fn response(ctx: &mut Context<()>) -> roa::Result {
    ctx.write_text("Hello, World");
    Ok(())
}

Error Handling

You can catch or straightly throw an error returned by next.

use roa::{App, Context, Next, 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>> {
    let app = App::new(())
        .gate(catch)
        .gate(not_catch)
        .end(error);
    app.listen("127.0.0.1:8000", |addr| {
        info!("Server is listening on {}", addr)
    })?
    .await?;
    Ok(())
}

async fn catch(_ctx: &mut Context<()>, next: Next<'_>) -> roa::Result {
    // catch
    if let Err(err) = next.await {
        // teapot is ok
        if err.status_code != StatusCode::IM_A_TEAPOT {
            return Err(err);
        }
    }
    Ok(())
}

async fn not_catch(ctx: &mut Context<()>, next: Next<'_>) -> roa::Result {
    next.await?; // just throw
    unreachable!()
}

async fn error(ctx: &mut Context<()>) -> roa::Result {
    throw!(StatusCode::IM_A_TEAPOT, "I'm a teapot!")
}

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, ErrorKind};
pub async fn error_handler<S>(ctx: &mut Context<S>, err: Error) -> Result {
    // set status code to err.status_code.
    ctx.resp.status = err.status_code;
    if err.expose {
        // write err.message to response body if err.expose.
        ctx.resp.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, get};
use roa::{App, Context};
use async_std::task::spawn;
use log::info;

#[async_std::main]
async fn main() -> Result<(), Box<dyn std::error::Error>> {
    let router = Router::new()
        .on("/:id", get(end)); // get dynamic "/:id"
    let app = App::new(())
        .end(router.routes("/user")?); // route with prefix "/user"
    app.listen("127.0.0.1:8000", |addr| {
        info!("Server is listening on {}", addr)
    })?
    .await?;
     
    Ok(())
}

async fn end(ctx: &mut Context<()>) -> roa::Result {
    // get "/user/1", then id == 1.
    let id: u64 = ctx.must_param("id")?.parse()?;
    // do something
    Ok(())
}

Query

Roa provides a middleware query_parser.

use roa::preload::*;
use roa::query::query_parser;
use roa::{App, Context};
use async_std::task::spawn;
use log::info;

async fn must(ctx: &mut Context<()>) -> roa::Result {
    // request "/?id=1", then id == 1.
    let id: u64 = ctx.must_query("id")?.parse()?;
    Ok(())
}

#[async_std::main]
async fn main() -> Result<(), Box<dyn std::error::Error>> {
    let app = App::new(())
        .gate(query_parser)
        .end(must);
    app.listen("127.0.0.1:8080", |addr| {
        info!("Server is listening on {}", addr)
    })?
    .await?;     
    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;

pub use roa_diesel as diesel;

pub use roa_tokio as tokio;

Modules

compress	The compress module of roa. This module provides a middleware `Compress`.
cookie	The cookie module of roa. This module provides a middleware `cookie_parser` and a context extension `Cookier`.
cors	The cors module of roa. This module provides a middleware `Cors`.
forward	The forward module of roa. This module provides a context extension `Forward`, which is used to parse `X-Forwarded-*` request headers.
header	The header module of roa. This module provides a Request/Response extension `FriendlyHeaders`.
http	A general purpose library of common HTTP types
jwt	The jwt module of roa. This module provides middlewares `guard` and `guard_by` and a context extension `JwtVerifier`.
logger	The logger module of roa. This module provides a middleware `logger`.
preload	Reexport all extensional traits.
query	The query module of roa. This module provides a middleware `query_parser` and a context extension `Query`.

Macros

throw

Throw an Err(Error).

Structs

AddrStream	A transport returned yieled by `AddrIncoming`.
App	The Application of roa.
Boxed	Boxed endpoint.
Chain	A middleware composing and executing other middlewares in a stack-like manner.
Context	A structure to share request, response and other data between middlewares.
Error	The `Error` of roa.
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.
Shared	Shared middleware.
Variable	A variable.

Enums

Body	The body of response.
ErrorKind	Kind of Error.

Traits

Accept	Asynchronously accept incoming connections.
Endpoint	Endpoint
EndpointExt	Extra methods of endpoint.
Middleware	Middleware
MiddlewareExt	A set of method to chain middleware/endpoint to middleware or make middleware shared.
Spawn	Executor constraint.
State	The `State` trait, should be replace with trait alias. The `App::state` will be cloned when a request inbounds.

Type Definitions

Next	Type of the second parameter in a middleware.
Result	Type alias for `StdResult<R, Error>`.
ResultFuture	Type alias for `Pin<Box<dyn 'a + Future<Output = Result<R>>>>`.

Attribute Macros

async_trait