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@ -9,7 +9,7 @@ weight: 170
Actix-web provides a facility for type-safe request information access called *extractors* Actix-web provides a facility for type-safe request information access called *extractors*
(ie, `impl FromRequest`). By default, actix-web provides several extractor implementations. (ie, `impl FromRequest`). By default, actix-web provides several extractor implementations.
An extractor can be accessed as an arguments to a handler function. Actix-web supports An extractor can be accessed as an argument to a handler function. Actix-web supports
up to 10 extractors per handler function. Argument position does not matter. up to 10 extractors per handler function. Argument position does not matter.
{{< include-example example="extractors" file="main.rs" section="option-one" >}} {{< include-example example="extractors" file="main.rs" section="option-one" >}}
@ -19,7 +19,7 @@ up to 10 extractors per handler function. Argument position does not matter.
[*Path*][pathstruct] provides information that can be extracted from the Request's [*Path*][pathstruct] provides information that can be extracted from the Request's
path. You can deserialize any variable segment from the path. path. You can deserialize any variable segment from the path.
For instance, for resource that registered for the `/users/{userid}/{friend}` path For instance, for resource that registered for the `/users/{userid}/{friend}` path,
two segments could be deserialized, `userid` and `friend`. These segments could be two segments could be deserialized, `userid` and `friend`. These segments could be
extracted into a `tuple`, i.e. `Path<(u32, String)>` or any structure that implements extracted into a `tuple`, i.e. `Path<(u32, String)>` or any structure that implements
the `Deserialize` trait from the *serde* crate. the `Deserialize` trait from the *serde* crate.
@ -45,14 +45,14 @@ query parameters. Underneath it uses *serde_urlencoded* crate.
# Json # Json
[*Json*][jsonstruct] allows to deserialize a request body into a struct. To extract [*Json*][jsonstruct] allows deserialization of a request body into a struct. To extract
typed information from a request's body, the type `T` must implement the `Deserialize` typed information from a request's body, the type `T` must implement the `Deserialize`
trait from *serde*. trait from *serde*.
{{< include-example example="extractors" file="json_one.rs" section="json-one" >}} {{< include-example example="extractors" file="json_one.rs" section="json-one" >}}
Some extractors provide a way to configure the extraction process. Json extractor Some extractors provide a way to configure the extraction process. Json extractor
[*JsonConfig*][jsonconfig] type for configuration. To configure an extractor, pass it's [*JsonConfig*][jsonconfig] type for configuration. To configure an extractor, pass its
configuration object to the resource's `.data()` method. In case of a *Json* extractor configuration object to the resource's `.data()` method. In case of a *Json* extractor
it returns a *JsonConfig*. You can configure the maximum size of the json payload as it returns a *JsonConfig*. You can configure the maximum size of the json payload as
well as a custom error handler function. well as a custom error handler function.
@ -63,7 +63,7 @@ The following example limits the size of the payload to 4kb and uses a custom er
# Form # Form
At the moment only url-encoded forms are supported. The url-encoded body could be At the moment, only url-encoded forms are supported. The url-encoded body could be
extracted to a specific type. This type must implement the `Deserialize` trait from extracted to a specific type. This type must implement the `Deserialize` trait from
the *serde* crate. the *serde* crate.
@ -92,10 +92,8 @@ Application state is accessible from the handler with the `web::Data` extractor;
however, state is accessible as a read-only reference. If you need mutable access to state, however, state is accessible as a read-only reference. If you need mutable access to state,
it must be implemented. it must be implemented.
> **Beware**, actix creates multiple copies of the application state and the handlers, > **Beware**, actix creates multiple copies of the application state and the handlers. It creates
> unique for each thread. If you run your application in several threads, actix will > one copy for each thread.
> create the same amount as number of threads of application state objects and handler
> objects.
Here is an example of a handler that stores the number of processed requests: Here is an example of a handler that stores the number of processed requests: