Struct Etag 

pub struct Etag { /* private fields */ }

Etag and If-None-Match header handler

Trillium handler that provides an outbound etag header after other handlers have been run, and if the request includes an if-none-match header, compares these values and sends a 304 not modified status, omitting the response body.

The conditional comparison applies only to GET and HEAD requests with successful responses; responses to other methods, error responses, and redirects pass through unchanged, and only successful responses receive a generated etag. Enforcing preconditions on state-changing requests — refusing the write with 412 Precondition Failed — requires knowing the resource’s entity tag before the write runs, so it is up to the application.

Streamed bodies

Note that this handler does not currently provide an etag trailer for streamed bodies, but may do so in the future.

Strong vs weak comparison

Etags can be compared using a strong method or a weak method. By default, this handler allows weak comparison. To change this setting, construct your handler with Etag::new().strong(). See etag::EntityTag for further documentation.

Implementations

impl Etag

pub fn new() -> Self

constructs a new Etag handler

pub fn strong(self) -> Self

Configures this handler to use strong content-based etag comparison only. See etag::EntityTag for further documentation on the differences between strong and weak etag comparison.

Trait Implementations

impl Clone for Etag

fn clone(&self) -> Etag

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Copy for Etag

impl Debug for Etag

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Default for Etag

fn default() -> Etag

Returns the “default value” for a type.

impl Handler for Etag

async fn run(&self, conn: Conn) -> Conn

Executes this handler, performing any modifications to the Conn that are desired.

async fn before_send(&self, conn: Conn) -> Conn

Performs any final modifications to this conn after all handlers have been run. Although this is a slight deviation from the simple conn->conn->conn chain represented by most Handlers, it provides an easy way for libraries to effectively inject a second handler into a response chain. This is useful for loggers that need to record information both before and after other handlers have run, as well as database transaction handlers and similar library code.

fn init(&mut self, info: &mut Info) -> impl Future<Output = ()> + Send

Performs one-time async set up on a mutable borrow of the Handler before the server starts accepting requests. This allows a Handler to be defined in synchronous code but perform async setup such as establishing a database connection or fetching some state from an external source. This is optional, and chances are high that you do not need this.

fn has_upgrade(&self, upgrade: &Upgrade) -> bool

predicate function answering the question of whether this Handler would like to take ownership of the negotiated Upgrade. If this returns true, you must implement Handler::upgrade. The first handler that responds true to this will receive ownership of the trillium::Upgrade in a subsequent call to Handler::upgrade

fn upgrade(&self, upgrade: Upgrade) -> impl Future<Output = ()> + Send

This will only be called if the handler reponds true to Handler::has_upgrade and will only be called once for this upgrade. There is no return value, and this function takes exclusive ownership of the underlying transport once this is called. You can downcast the transport to whatever the source transport type is and perform any non-http protocol communication that has been negotiated. You probably don’t want this unless you’re implementing something like websockets. Please note that for many transports such as TcpStreams, dropping the transport (and therefore the Upgrade) will hang up / disconnect.

fn name(&self) -> Cow<'static, str>

Customize the name of your handler. This is used in Debug implementations. The default is the type name of this handler.