mirror of
https://github.com/actix/actix-website
synced 2024-11-30 19:14:36 +01:00
137 lines
5.7 KiB
Markdown
137 lines
5.7 KiB
Markdown
---
|
|
title: Middleware
|
|
menu: docs_advanced
|
|
weight: 220
|
|
---
|
|
|
|
# Middleware
|
|
|
|
Actix-web's middleware system allows us to add additional behavior to request/response
|
|
processing. Middleware can hook into an incoming request process, enabling us to modify
|
|
requests as well as halt request processing to return a response early.
|
|
|
|
Middleware can also hook into response processing.
|
|
|
|
Typically, middleware is involved in the following actions:
|
|
|
|
* Pre-process the Request
|
|
* Post-process a Response
|
|
* Modify application state
|
|
* Access external services (redis, logging, sessions)
|
|
|
|
Middleware is registered for each `App`, `scope`, or `Resource` and executed in opposite
|
|
order as registration. In general, a *middleware* is a type that implements the
|
|
[*Service trait*][servicetrait] and [*Transform trait*][transformtrait]. Each method in
|
|
the traits has a default implementation. Each method can return a result immediately
|
|
or a *future* object.
|
|
|
|
The following demonstrates creating a simple middleware:
|
|
|
|
{{< include-example example="middleware" file="main.rs" section="simple" >}}
|
|
|
|
Alternatively, for simple use cases, you can use [*wrap_fn*][wrap_fn] to create small, ad-hoc middleware:
|
|
|
|
{{< include-example example="middleware" file="wrap_fn.rs" section="wrap-fn" >}}
|
|
|
|
> Actix-web provides several useful middleware, such as *logging*, *user sessions*,
|
|
> *compress*, etc.
|
|
|
|
# Logging
|
|
|
|
Logging is implemented as a middleware. It is common to register a logging middleware
|
|
as the first middleware for the application. Logging middleware must be registered for
|
|
each application.
|
|
|
|
The `Logger` middleware uses the standard log crate to log information. You should enable logger
|
|
for *actix_web* package to see access log ([env_logger][envlogger] or similar).
|
|
|
|
## Usage
|
|
|
|
Create `Logger` middleware with the specified `format`. Default `Logger` can be created
|
|
with `default` method, it uses the default format:
|
|
|
|
```ignore
|
|
%a %t "%r" %s %b "%{Referer}i" "%{User-Agent}i" %T
|
|
```
|
|
|
|
{{< include-example example="middleware" file="logger.rs" section="logger" >}}
|
|
|
|
The following is an example of the default logging format:
|
|
|
|
```
|
|
INFO:actix_web::middleware::logger: 127.0.0.1:59934 [02/Dec/2017:00:21:43 -0800] "GET / HTTP/1.1" 302 0 "-" "curl/7.54.0" 0.000397
|
|
INFO:actix_web::middleware::logger: 127.0.0.1:59947 [02/Dec/2017:00:22:40 -0800] "GET /index.html HTTP/1.1" 200 0 "-" "Mozilla/5.0 (Macintosh; Intel Mac OS X 10.13; rv:57.0) Gecko/20100101 Firefox/57.0" 0.000646
|
|
```
|
|
|
|
## Format
|
|
|
|
- `%%` The percent sign
|
|
- `%a` Remote IP-address (IP-address of proxy if using reverse proxy)
|
|
- `%t` Time when the request was started to process
|
|
- `%P` The process ID of the child that serviced the request
|
|
- `%r` First line of request
|
|
- `%s` Response status code
|
|
- `%b` Size of response in bytes, including HTTP headers
|
|
- `%T` Time taken to serve the request, in seconds with floating fraction in .06f format
|
|
- `%D` Time taken to serve the request, in milliseconds
|
|
- `%{FOO}i` request.headers['FOO']
|
|
- `%{FOO}o` response.headers['FOO']
|
|
- `%{FOO}e` os.environ['FOO']
|
|
|
|
## Default headers
|
|
|
|
To set default response headers, the `DefaultHeaders` middleware can be used. The
|
|
*DefaultHeaders* middleware does not set the header if response headers already contain
|
|
a specified header.
|
|
|
|
{{< include-example example="middleware" file="default_headers.rs" section="default-headers" >}}
|
|
|
|
## User sessions
|
|
|
|
Actix-web provides a general solution for session management. The
|
|
[**actix-session**][actixsession] middleware can use multiple backend types to store session data.
|
|
|
|
> By default, only cookie session backend is implemented. Other backend implementations
|
|
> can be added.
|
|
|
|
[**CookieSession**][cookiesession] uses cookies as session storage. `CookieSessionBackend`
|
|
creates sessions which are limited to storing fewer than 4000 bytes of data, as the payload
|
|
must fit into a single cookie. An internal server error is generated if a session
|
|
contains more than 4000 bytes.
|
|
|
|
A cookie may have a security policy of *signed* or *private*. Each has a respective
|
|
`CookieSession` constructor.
|
|
|
|
A *signed* cookie may be viewed but not modified by the client. A *private* cookie may
|
|
neither be viewed nor modified by the client.
|
|
|
|
The constructors take a key as an argument. This is the private key for cookie session -
|
|
when this value is changed, all session data is lost.
|
|
|
|
In general, you create a `SessionStorage` middleware and initialize it with specific
|
|
backend implementation, such as a `CookieSession`. To access session data the
|
|
[`Session`][requestsession] extractor must be used. This method returns a
|
|
[*Session*][sessionobj] object, which allows us to get or set session data.
|
|
|
|
{{< include-example example="middleware" file="user_sessions.rs" section="user-session" >}}
|
|
|
|
# Error handlers
|
|
|
|
`ErrorHandlers` middleware allows us to provide custom handlers for responses.
|
|
|
|
You can use the `ErrorHandlers::handler()` method to register a custom error handler
|
|
for a specific status code. You can modify an existing response or create a completly new
|
|
one. The error handler can return a response immediately or return a future that resolves
|
|
into a response.
|
|
|
|
{{< include-example example="middleware" file="errorhandler.rs" section="error-handler" >}}
|
|
|
|
[sessionobj]: https://docs.rs/actix-session/0.3.0/actix_session/struct.Session.html
|
|
[requestsession]: https://docs.rs/actix-session/0.3.0/actix_session/struct.Session.html
|
|
[cookiesession]: https://docs.rs/actix-session/0.3.0/actix_session/struct.CookieSession.html
|
|
[actixsession]: https://docs.rs/actix-session/0.3.0/actix_session/
|
|
[envlogger]: https://docs.rs/env_logger/*/env_logger/
|
|
[servicetrait]: https://docs.rs/actix-web/3/actix_web/dev/trait.Service.html
|
|
[transformtrait]: https://docs.rs/actix-web/3/actix_web/dev/trait.Transform.html
|
|
[wrap_fn]: https://docs.rs/actix-web/3/actix_web/struct.App.html#method.wrap_fn
|