examples: Replaced custom Json extractor with WithRejection

examples/customize-extractor-error/Cargo.toml

@@ -6,6 +6,7 @@ publish = false
 
 [dependencies]
 axum = { path = "../../axum" }
+axum-extra = { path = "../../axum-extra" }
 serde = { version = "1.0", features = ["derive"] }
 serde_json = "1.0"
 tokio = { version = "1.0", features = ["full"] }

examples/customize-extractor-error/src/main.rs

@@ -5,15 +5,15 @@
 //! ```
 
 use axum::{
-    async_trait,
-    extract::{rejection::JsonRejection, FromRequest, RequestParts},
+    extract::rejection::JsonRejection,
     http::StatusCode,
-    routing::post,
-    BoxError, Router,
+    response::IntoResponse,
+    routing::post, Json, Router,
 };
-use serde::{de::DeserializeOwned, Deserialize};
-use serde_json::{json, Value};
-use std::{borrow::Cow, net::SocketAddr};
+use axum_extra::extract::WithRejection;
+use serde::Deserialize;
+use serde_json::json;
+use std::net::SocketAddr;
 use tracing_subscriber::{layer::SubscriberExt, util::SubscriberInitExt};
 
 #[tokio::main]
@@ -38,7 +38,12 @@ async fn main() {
         .unwrap();
 }
 
-async fn handler(Json(user): Json<User>) {
+async fn handler(
+    // `WithRejection` will extract `Json<User>` from the request. If the
+    // extraction fails, a `MyRejection` will be created from `JsonResponse` and
+    // returned to the client
+    WithRejection(Json(user), _): WithRejection<Json<User>, MyRejection>
+) {
     dbg!(&user);
 }
 
@@ -49,46 +54,44 @@ struct User {
     username: String,
 }
 
-// We define our own `Json` extractor that customizes the error from `axum::Json`
-struct Json<T>(T);
-
-#[async_trait]
-impl<B, T> FromRequest<B> for Json<T>
-where
-    // these trait bounds are copied from `impl FromRequest for axum::Json`
-    T: DeserializeOwned,
-    B: axum::body::HttpBody + Send,
-    B::Data: Send,
-    B::Error: Into<BoxError>,
-{
-    type Rejection = (StatusCode, axum::Json<Value>);
+// Define your own custom rejection
+#[derive(Debug)]
+struct MyRejection {
+    body: String,
+    status: StatusCode,
+}
 
-    async fn from_request(req: &mut RequestParts<B>) -> Result<Self, Self::Rejection> {
-        match axum::Json::<T>::from_request(req).await {
-            Ok(value) => Ok(Self(value.0)),
-            Err(rejection) => {
-                // convert the error from `axum::Json` into whatever we want
-                let (status, body): (_, Cow<'_, str>) = match rejection {
-                    JsonRejection::JsonDataError(err) => (
-                        StatusCode::BAD_REQUEST,
-                        format!("Invalid JSON request: {}", err).into(),
-                    ),
-                    JsonRejection::MissingJsonContentType(err) => {
-                        (StatusCode::BAD_REQUEST, err.to_string().into())
-                    }
-                    err => (
-                        StatusCode::INTERNAL_SERVER_ERROR,
-                        format!("Unknown internal error: {}", err).into(),
-                    ),
-                };
+// `IntoResponse` is required for your custom rejection type
+impl IntoResponse for MyRejection {
+    fn into_response(self) -> axum::response::Response {
+        let Self { body, status } = self;
+        (
+            status,
+            // we use `axum::Json` here to generate a JSON response
+            // body but you can use whatever response you want
+            axum::Json(json!({ "error": body })),
+        )
+            .into_response()
+    }
+}
 
-                Err((
-                    status,
-                    // we use `axum::Json` here to generate a JSON response
-                    // body but you can use whatever response you want
-                    axum::Json(json!({ "error": body })),
-                ))
+// Implement `From` for any Rejection type you want
+impl From<JsonRejection> for MyRejection {
+    fn from(rejection: JsonRejection) -> Self {
+        // convert the error from `axum::Json` into whatever we want
+        let (status, body) = match rejection {
+            JsonRejection::JsonDataError(err) => (
+                StatusCode::BAD_REQUEST,
+                format!("Invalid JSON request: {}", err),
+            ),
+            JsonRejection::MissingJsonContentType(err) => {
+                (StatusCode::BAD_REQUEST, err.to_string())
             }
-        }
+            err => (
+                StatusCode::INTERNAL_SERVER_ERROR,
+                format!("Unknown internal error: {}", err),
+            ),
+        };
+        Self { body, status }
     }
 }