example: add AddData Middleware example (refs #445) (#728)

* example: add AddData Middleware example (refs #445)

* fix name

examples/poem/add-data/Cargo.toml

@@ -0,0 +1,10 @@
+[package]
+name = "example-add-data"
+version.workspace = true
+edition.workspace = true
+publish.workspace = true
+
+[dependencies]
+poem.workspace = true
+tokio = { workspace = true, features = ["rt-multi-thread", "macros"] }
+tracing-subscriber.workspace = true

examples/poem/add-data/src/main.rs

@@ -0,0 +1,52 @@
+use std::{
+    collections::HashMap,
+    sync::{Arc, Mutex},
+};
+
+use poem::{
+    get, handler,
+    listener::TcpListener,
+    middleware::AddData,
+    web::{Data, Path},
+    EndpointExt, Route, Server,
+};
+
+struct AppState {
+    clients: Mutex<HashMap<String, String>>,
+}
+
+#[handler]
+fn set_state(Path(name): Path<String>, state: Data<&Arc<AppState>>) -> String {
+    let mut store = state.clients.lock().unwrap();
+    store.insert(name.to_string(), "some state object".to_string());
+    "store updated".to_string()
+}
+
+#[handler]
+fn get_state(Path(name): Path<String>, state: Data<&Arc<AppState>>) -> String {
+    let store = state.clients.lock().unwrap();
+    let message = store.get(&name).unwrap();
+    message.to_string()
+}
+
+#[tokio::main]
+async fn main() -> Result<(), std::io::Error> {
+    if std::env::var_os("RUST_LOG").is_none() {
+        std::env::set_var("RUST_LOG", "poem=debug");
+    }
+    tracing_subscriber::fmt::init();
+
+    let state = Arc::new(AppState {
+        clients: Mutex::new(HashMap::new()),
+    });
+
+    let app = Route::new()
+        .at("/hello/:name", get(set_state))
+        .at("/:name", get(get_state))
+        .with(AddData::new(state));
+
+    Server::new(TcpListener::bind("0.0.0.0:3000"))
+        .name("add-data")
+        .run(app)
+        .await
+}