Trait tower_web::middleware::Middleware[−][src]

pub trait Middleware<S> {
    type Request;
    type Response;
    type Error;
    type Service: Service<Request = Self::Request, Response = Self::Response, Error = Self::Error>;
    fn wrap(&self, inner: S) -> Self::Service;

    fn chain<T>(self, middleware: T) -> Chain<Self, T>
    where
        T: Middleware<Self::Service>,
        Self: Sized,
    { ... }
}

Decorates a Service, transforming either the request or the response.

Often, many of the pieces needed for writing network applications can be reused across multiple services. The Middleware trait can be used to write reusable components that can be applied to very different kinds of services; for example, it can be applied to services operating on different protocols, and to both the client and server side of a network transaction.

Log

Take request logging as an example:

use tower_service::Service;
use tower_web::middleware::Middleware;
use futures::{Future, Poll};

use std::fmt;

pub struct LogMiddleware {
    target: &'static str,
}

impl<S> Middleware<S> for LogMiddleware
where
    S: Service,
    S::Request: fmt::Debug,
{
    type Request = S::Request;
    type Response = S::Response;
    type Error = S::Error;
    type Service = LogService<S>;

    fn wrap(&self, service: S) -> LogService<S> {
        LogService {
            target: self.target,
            service
        }
    }
}

// This service implements the Log behavior
pub struct LogService<S> {
    target: &'static str,
    service: S,
}

impl<S> Service for LogService<S>
where
    S: Service,
    S::Request: fmt::Debug,
{
    type Request = S::Request;
    type Response = S::Response;
    type Error = S::Error;
    type Future = S::Future;

    fn poll_ready(&mut self) -> Poll<(), Self::Error> {
        self.service.poll_ready()
    }

    fn call(&mut self, request: Self::Request) -> Self::Future {
        info!(target: self.target, "request = {:?}", request);
        self.service.call(request)
    }
}

The above log implementation is decoupled from the underlying protocol and is also decoupled from client or server concerns. In other words, the same log middleware could be used in either a client or a server.

Associated Types

The wrapped service request type

The wrapped service response type

The wrapped service's error type

The wrapped service

Required Methods

Wrap the given service with the middleware, returning a new service that has been decorated with the middleware.

Provided Methods

Return a new Middleware instance that applies both self and middleware to services being wrapped.

This defines a middleware stack.

Implementors