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//! Defines types for handlers, the primary building block of a Gotham application. //! //! A function can be used directly as a handler using one of the default implementations of //! `Handler`, but the traits can also be implemented directly for greater control. See the //! `Handler` trait for some examples of valid handlers. use std::borrow::Cow; use std::panic::RefUnwindSafe; use bytes::Bytes; use futures::{future, Future}; use hyper::{Body, Chunk, Response, StatusCode}; use mime::{self, Mime}; use crate::helpers::http::response; use crate::state::State; mod error; use crate::error::*; /// Defines handlers for serving static assets. pub mod assets; pub use self::error::{HandlerError, IntoHandlerError}; /// A type alias for the trait objects returned by `HandlerService`. /// /// When the `Future` resolves to an error, the `(State, HandlerError)` value is used to generate /// an appropriate HTTP error response. pub type HandlerFuture = dyn Future<Item = (State, Response<Body>), Error = (State, HandlerError)> + Send; /// A `Handler` is an asynchronous function, taking a `State` value which represents the request /// and related runtime state, and returns a future which resolves to a response. /// /// This represents the common entry point for the parts of a Gotham application, and is used with /// the `Router` API to describe how a request should be dispatched and handled. /// /// The `Handler` is created and consumed by each request. In the most common case (a bare function /// acting as a `Handler`) the `Handler + Copy` traits allow the `Handler` to be copied for each /// request, and the copy consumed. For a closure or a custom handler, the `NewHandler` /// implementation creates a `Handler` value for each request. /// /// # Examples /// /// The simplest kind of handler is a bare function which returns a synchronous response. This is /// useful when we don't need to do any I/O before generating a response. /// /// ```rust /// # extern crate gotham; /// # extern crate hyper; /// # /// # use hyper::{Body, Response}; /// # use gotham::handler::Handler; /// # use gotham::state::State; /// # /// # fn main() { /// fn my_handler(_state: State) -> (State, Response<Body>) { /// // Implementation elided. /// # unimplemented!() /// } /// # /// # fn assert_type<H>(_h: H) where H: Handler + Copy {} /// # assert_type(my_handler); /// # } /// ``` /// /// An asynchronous handler returns a `HandlerFuture` that will resolve to the response. For /// example, this allows I/O work to begin, and for the Gotham app to continue generating a /// response once the work completes. /// /// ```rust /// # extern crate gotham; /// # extern crate hyper; /// # /// # use gotham::handler::{Handler, HandlerFuture}; /// # use gotham::state::State; /// # /// # fn main() { /// fn async_handler(_state: State) -> Box<HandlerFuture> { /// // Implementation elided. /// # unimplemented!() /// } /// # /// # fn assert_type<H>(_h: H) where H: Handler + Copy {} /// # assert_type(async_handler); /// # } /// ``` /// /// A closure can implement `Handler` automatically, in the same way as a bare function. When /// constructing a `Handler` in this way, a wrapping closure must also be used to implement the /// `NewHandler` trait. /// /// ```rust /// # extern crate gotham; /// # extern crate hyper; /// # extern crate futures; /// # /// # use gotham::handler::{HandlerFuture, NewHandler}; /// # use gotham::state::State; /// # use futures::future; /// # /// # fn main() { /// let new_handler = || { /// let handler = |_state: State| { /// // Implementation elided. /// # Box::new(future::empty()) as Box<HandlerFuture> /// }; /// Ok(handler) /// }; /// /// // Pass `new_handler` to the router, using the `to_new_handler` API. /// # /// # fn assert_type<H>(_h: H) where H: NewHandler {} /// # assert_type(new_handler); /// # } /// ``` /// /// A custom handler, which implements the `NewHandler` and `Handler` traits directly for greater /// control. See the `NewHandler` trait for more examples of custom handlers. /// /// ```rust /// # extern crate gotham; /// # extern crate hyper; /// # /// # use gotham::handler::{Handler, HandlerFuture, NewHandler}; /// # use gotham::state::State; /// # use gotham::error::*; /// # /// # fn main() { /// #[derive(Copy, Clone)] /// struct MyCustomHandler; /// /// impl NewHandler for MyCustomHandler { /// type Instance = Self; /// /// fn new_handler(&self) -> Result<Self::Instance> { /// Ok(*self) /// } /// } /// /// impl Handler for MyCustomHandler { /// fn handle(self, _state: State) -> Box<HandlerFuture> { /// // Implementation elided. /// # unimplemented!() /// } /// } /// # /// # fn assert_type<H>(_h: H) where H: NewHandler {} /// # assert_type(MyCustomHandler); /// # } /// ``` pub trait Handler: Send { /// Handles the request, returning a boxed future which resolves to a response. fn handle(self, state: State) -> Box<HandlerFuture>; } impl<F, R> Handler for F where F: FnOnce(State) -> R + Send, R: IntoHandlerFuture, { fn handle(self, state: State) -> Box<HandlerFuture> { self(state).into_handler_future() } } /// A type which is used to spawn new `Handler` values. When implementing a custom `Handler` type, /// this is used to define how instances of the `Handler` are created. /// /// The `Instance` associated type is usually `Self` in the simple case, but can be a different /// type where greater control is needed over lifetimes. /// /// # Examples /// /// A custom handler which implements `NewHandler` by copying itself. /// /// ```rust /// # extern crate gotham; /// # extern crate hyper; /// # /// # use gotham::handler::{Handler, HandlerFuture, NewHandler}; /// # use gotham::state::State; /// # use gotham::error::*; /// # /// # fn main() { /// #[derive(Copy, Clone)] /// struct MyCustomHandler; /// /// impl NewHandler for MyCustomHandler { /// type Instance = Self; /// /// fn new_handler(&self) -> Result<Self::Instance> { /// Ok(*self) /// } /// } /// /// impl Handler for MyCustomHandler { /// fn handle(self, _state: State) -> Box<HandlerFuture> { /// // Implementation elided. /// # unimplemented!() /// } /// } /// # /// # fn assert_type<H>(_h: H) where H: NewHandler {} /// # assert_type(MyCustomHandler); /// # } /// ``` /// /// A custom handler which implements `NewHandler` using a specific `Instance` type. /// /// ```rust /// # extern crate gotham; /// # extern crate hyper; /// # /// # use gotham::handler::{Handler, HandlerFuture, NewHandler}; /// # use gotham::state::State; /// # use gotham::error::*; /// # /// # fn main() { /// #[derive(Copy, Clone)] /// struct MyValueInstantiatingHandler; /// /// impl NewHandler for MyValueInstantiatingHandler { /// type Instance = MyHandler; /// /// fn new_handler(&self) -> Result<Self::Instance> { /// Ok(MyHandler) /// } /// } /// /// struct MyHandler; /// /// impl Handler for MyHandler { /// fn handle(self, _state: State) -> Box<HandlerFuture> { /// // Implementation elided. /// # unimplemented!() /// } /// } /// # /// # fn assert_type<H>(_h: H) where H: NewHandler {} /// # assert_type(MyValueInstantiatingHandler); /// # } /// ``` pub trait NewHandler: Send + Sync + RefUnwindSafe { /// The type of `Handler` created by the `NewHandler`. type Instance: Handler + Send; /// Create and return a new `Handler` value. fn new_handler(&self) -> Result<Self::Instance>; } impl<F, H> NewHandler for F where F: Fn() -> Result<H> + Send + Sync + RefUnwindSafe, H: Handler + Send, { type Instance = H; fn new_handler(&self) -> Result<H> { self() } } /// Represents a type which can be converted into the future type returned by a `Handler`. /// /// This is used to allow functions with different return types to satisfy the `Handler` trait /// bound via the generic function implementation. pub trait IntoHandlerFuture { /// Converts this value into a boxed future resolving to a state and response. fn into_handler_future(self) -> Box<HandlerFuture>; } impl<T> IntoHandlerFuture for (State, T) where T: IntoResponse, { fn into_handler_future(self) -> Box<HandlerFuture> { let (state, t) = self; let response = t.into_response(&state); Box::new(future::ok((state, response))) } } impl IntoHandlerFuture for Box<HandlerFuture> { fn into_handler_future(self) -> Box<HandlerFuture> { self } } /// Represents a type which can be converted to a response. This trait is used in converting the /// return type of a function into a response. /// /// # Examples /// /// ```rust /// # #![allow(deprecated)] // TODO: Refactor this. /// # /// # extern crate gotham; /// # extern crate hyper; /// # /// # use gotham::state::State; /// # use gotham::pipeline::set::*; /// # use gotham::router::Router; /// # use gotham::router::route::{RouteImpl, Extractors, Delegation}; /// # use gotham::router::tree::Tree; /// # use gotham::router::route::matcher::MethodOnlyRouteMatcher; /// # use gotham::router::route::dispatch::DispatcherImpl; /// # use gotham::handler::IntoResponse; /// # use gotham::extractor::{NoopPathExtractor, NoopQueryStringExtractor}; /// # use gotham::router::response::finalizer::ResponseFinalizerBuilder; /// # use hyper::Method; /// # use hyper::StatusCode; /// # use hyper::{Body, Response}; /// # /// struct MyStruct { /// value: String /// } /// /// impl MyStruct { /// fn new() -> MyStruct { /// // ... /// # MyStruct { value: "".to_owned() } /// } /// } /// /// impl IntoResponse for MyStruct { /// fn into_response(self, _state: &State) -> Response<Body> { /// Response::builder() /// .status(StatusCode::OK) /// .body(self.value.into()) /// .unwrap() /// } /// } /// /// fn handler(state: State) -> (State, MyStruct) { /// (state, MyStruct::new()) /// } /// /// # fn main() { /// # let mut tree = Tree::new(); /// # let pipeline_set = finalize_pipeline_set(new_pipeline_set()); /// # let finalizer = ResponseFinalizerBuilder::new().finalize(); /// # let matcher = MethodOnlyRouteMatcher::new(vec![Method::GET]); /// # let dispatcher = DispatcherImpl::new(|| Ok(handler), (), pipeline_set); /// # let extractors: Extractors<NoopPathExtractor, NoopQueryStringExtractor> = Extractors::new(); /// # let route = RouteImpl::new(matcher, Box::new(dispatcher), extractors, Delegation::Internal); /// tree.add_route(Box::new(route)); /// Router::new(tree, finalizer); /// # } /// ``` pub trait IntoResponse { /// Converts this value into a `hyper::Response` fn into_response(self, state: &State) -> Response<Body>; } impl IntoResponse for Response<Body> { fn into_response(self, _state: &State) -> Response<Body> { self } } impl<T, E> IntoResponse for ::std::result::Result<T, E> where T: IntoResponse, E: IntoResponse, { fn into_response(self, state: &State) -> Response<Body> { match self { Ok(res) => res.into_response(state), Err(e) => e.into_response(state), } } } impl<B> IntoResponse for (Mime, B) where B: Into<Body>, { fn into_response(self, state: &State) -> Response<Body> { (StatusCode::OK, self.0, self.1).into_response(state) } } impl<B> IntoResponse for (StatusCode, Mime, B) where B: Into<Body>, { fn into_response(self, state: &State) -> Response<Body> { response::create_response(state, self.0, self.1, self.2) } } // derive IntoResponse for Into<Body> types macro_rules! derive_into_response { ($type:ty) => { impl IntoResponse for $type { fn into_response(self, state: &State) -> Response<Body> { (StatusCode::OK, mime::TEXT_PLAIN, self).into_response(state) } } }; } // derive Into<Body> types - this is required because we // can't impl IntoResponse for Into<Body> due to Response<T> // and the potential it will add Into<Body> in the future derive_into_response!(Bytes); derive_into_response!(Chunk); derive_into_response!(String); derive_into_response!(Vec<u8>); derive_into_response!(&'static str); derive_into_response!(&'static [u8]); derive_into_response!(Cow<'static, str>); derive_into_response!(Cow<'static, [u8]>);