diff --git a/examples/Cargo.toml b/examples/Cargo.toml
index 2c6ce528..e5953058 100644
--- a/examples/Cargo.toml
+++ b/examples/Cargo.toml
@@ -4,6 +4,7 @@ members = [
     "cloudflare-worker",
     "compression",
     "cookie",
+    "dependency-injection",
     "error-handle",
     "file",
     "grpc",
diff --git a/examples/dependency-injection/Cargo.toml b/examples/dependency-injection/Cargo.toml
new file mode 100644
index 00000000..bd601239
--- /dev/null
+++ b/examples/dependency-injection/Cargo.toml
@@ -0,0 +1,7 @@
+[package]
+name = "dependency-injection"
+version = "0.1.0"
+edition = "2021"
+
+[dependencies]
+xitca-web = "0.2.2"
diff --git a/examples/dependency-injection/src/main.rs b/examples/dependency-injection/src/main.rs
new file mode 100644
index 00000000..f4568bd5
--- /dev/null
+++ b/examples/dependency-injection/src/main.rs
@@ -0,0 +1,48 @@
+//! example for using trait object as application state.
+
+use std::sync::Arc;
+
+use xitca_web::{
+    handler::{handler_service, state::StateRef},
+    route::get,
+    App,
+};
+
+fn main() -> std::io::Result<()> {
+    App::new()
+        // use trait object as application state
+        .with_state(object_state())
+        // extract trait object in handler
+        .at("/", get(handler_service(handler)))
+        .serve()
+        .bind("127.0.0.1:8080")?
+        .run()
+        .wait()
+}
+
+// a simple trait for injecting dependent type and logic to application.
+trait DI {
+    fn name(&self) -> &'static str;
+}
+
+// thread safe trait object state constructor.
+fn object_state() -> Arc<dyn DI + Send + Sync> {
+    // a dummy type implementing DI trait.
+    struct Foo;
+
+    impl DI for Foo {
+        fn name(&self) -> &'static str {
+            "foo"
+        }
+    }
+
+    // only this function knows the exact type implementing DI trait.
+    // everywhere else in the application it's only known as dyn DI trait object.
+    Arc::new(Foo)
+}
+
+// StateRef extractor is able extract &dyn DI from application state.
+async fn handler(StateRef(obj): StateRef<'_, dyn DI + Send + Sync>) -> String {
+    // get request to "/" path should return "hello foo" string response.
+    format!("hello {}", obj.name())
+}
diff --git a/test/Cargo.toml b/test/Cargo.toml
index fd965d60..215896e4 100644
--- a/test/Cargo.toml
+++ b/test/Cargo.toml
@@ -8,13 +8,13 @@ io-uring = ["xitca-http/io-uring", "xitca-server/io-uring"]
 
 [dependencies]
 xitca-client = { version = "0.1", features = ["http2", "http3", "websocket", "dangerous"] }
-xitca-http = { version = "0.2", features = ["http2", "http3"] }
+xitca-http = { version = "0.2.1", features = ["http2", "http3"] }
 xitca-codegen = "0.1"
 xitca-io = "0.1"
 xitca-server = { version = "0.1", features = ["http3"] }
 xitca-service = "0.1"
 xitca-unsafe-collection = "0.1"
-xitca-web = "0.2"
+xitca-web = "0.2.2"
 
 http-ws = { version = "0.2", features = ["stream"] }
 
diff --git a/web/CHANGES.md b/web/CHANGES.md
index b66e42f3..d12c6217 100644
--- a/web/CHANGES.md
+++ b/web/CHANGES.md
@@ -1,4 +1,6 @@
-# unreleased 0.2.2
+# unreleased
+
+# 0.2.2
 ## Add
 - `StateRef` can used for extracting `?Sized` type from application state.