examples(error-handling): custom_extractor

examples/error-handling/Cargo.toml

@@ -6,7 +6,7 @@ edition = "2021"
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
 
 [dependencies]
-axum = { path = "../../axum" }
+axum = { path = "../../axum", features=["matched-path"] }
 axum-extra = { path = "../../axum-extra" }
 chrono = { version = "0.4", features = ["serde"] }
 serde = { version = "1.0", features = ["derive"] }

examples/error-handling/src/custom_extractor.rs

@@ -0,0 +1,59 @@
+use axum::extract::MatchedPath;
+use axum::{
+    async_trait,
+    extract::{rejection::JsonRejection, FromRequest, RequestParts},
+    http::StatusCode,
+    response::IntoResponse,
+    BoxError,
+};
+use chrono::Utc;
+use serde::de::DeserializeOwned;
+use serde_json::{json, Value};
+
+pub async fn handler(Json(value): Json<Value>) -> impl IntoResponse {
+    Json(dbg!(value));
+}
+
+// We define our own `Json` extractor that customizes the error from `axum::Json`
+pub struct Json<T>(T);
+
+#[async_trait]
+impl<S, B, T> FromRequest<S, B> for Json<T>
+where
+    S: Send + Sync,
+    // 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>);
+
+    async fn from_request(req: &mut RequestParts<S, 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 path = req
+                    .extensions()
+                    .get::<MatchedPath>()
+                    .map(|x| x.as_str().to_owned());
+
+                let payload = json!({
+                    "message": rejection.to_string(),
+                    "timestamp": Utc::now(),
+                    "origin": "custom_extractor",
+                    "path": path,
+                });
+
+                let code = match rejection {
+                    JsonRejection::JsonDataError(_) | JsonRejection::MissingJsonContentType(_) => {
+                        StatusCode::BAD_REQUEST
+                    }
+                    _ => StatusCode::INTERNAL_SERVER_ERROR,
+                };
+                Err((code, axum::Json(payload)))
+            }
+        }
+    }
+}

examples/error-handling/src/main.rs

@@ -1,24 +1,23 @@
 mod with_rejection;
+mod custom_extractor;
 
+use axum::{routing::get, Router, Server};
 use std::net::SocketAddr;
-use axum::{Server, Router, routing::get};
 use tracing_subscriber::{layer::SubscriberExt, util::SubscriberInitExt};
 
-
-
 #[tokio::main]
 async fn main() {
     tracing_subscriber::registry()
         .with(tracing_subscriber::EnvFilter::new(
-            std::env::var("RUST_LOG")
-                .unwrap_or_else(|_| "error_handling=debug".into()),
+            std::env::var("RUST_LOG").unwrap_or_else(|_| "error_handling=debug".into()),
         ))
         .with(tracing_subscriber::fmt::layer())
         .init();
 
     // Build our application with some routes
     let app = Router::new()
-        .route("/withRejection", get(with_rejection::handler));
+        .route("/withRejection", get(with_rejection::handler))
+        .route("/customExtractor", get(custom_extractor::handler));
 
     // Run our application
     let addr = SocketAddr::from(([127, 0, 0, 1], 3000));
@@ -27,4 +26,4 @@ async fn main() {
         .serve(app.into_make_service())
         .await
         .unwrap();
-}
+}