First pass at Handlers chapter.

examples/request-handlers/Cargo.toml

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+[package]
+name = "request-handlers"
+version = "0.1.0"
+edition = "2018"
+
+[dependencies]
+actix-web = "0.7"
+actix = "0.7"

examples/request-handlers/src/handlers_arc.rs

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+// <arc>
+use actix_web::{dev::Handler, server, App, HttpRequest, HttpResponse};
+use std::sync::atomic::{AtomicUsize, Ordering};
+use std::sync::Arc;
+
+struct MyHandler(Arc<AtomicUsize>);
+
+impl<S> Handler<S> for MyHandler {
+    type Result = HttpResponse;
+
+    /// Handle request
+    fn handle(&self, _req: &HttpRequest<S>) -> Self::Result {
+        self.0.fetch_add(1, Ordering::Relaxed);
+        HttpResponse::Ok().into()
+    }
+}
+
+pub fn main() {
+    let sys = actix::System::new("example");
+
+    let inc = Arc::new(AtomicUsize::new(0));
+
+    server::new(move || {
+        let cloned = inc.clone();
+        App::new().resource("/", move |r| r.h(MyHandler(cloned)))
+    })
+    .bind("127.0.0.1:8088")
+    .unwrap()
+    .start();
+
+    println!("Started http server: 127.0.0.1:8088");
+    let _ = sys.run();
+}
+// </arc>

examples/request-handlers/src/main.rs

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+mod handlers_arc;
+// <main>
+use actix_web::{dev::Handler, server, App, HttpRequest, HttpResponse};
+use std::cell::Cell;
+
+struct MyHandler(Cell<usize>);
+
+impl<S> Handler<S> for MyHandler {
+    type Result = HttpResponse;
+
+    /// Handle request
+    fn handle(&self, _req: &HttpRequest<S>) -> Self::Result {
+        let i = self.0.get();
+        self.0.set(i + 1);
+        HttpResponse::Ok().into()
+    }
+}
+
+fn main() {
+    server::new(|| App::new().resource("/", |r| r.h(MyHandler(Cell::new(0))))) //use r.h() to bind handler, not the r.f()
+        .bind("127.0.0.1:8088")
+        .unwrap()
+        .run();
+}
+// </main>