async fn index(_: Request) -> Result<&'static str> {
Ok(“Hello Viz”)
}
#[tokio::main]
async fn main() -> Result<()> {
let addr = SocketAddr::from(([127, 0, 0, 1], 3000));
println!(“listening on {}”, addr);
let app = Router::new().get("/", index);if let Err(err) = Server::bind(&addr) .serve(ServiceMaker::from(app)) .await{ println!("{}", err);}Ok(())}
### 4. 运行结果如果你以上步骤没有出错，那么在终端中运行cargo run
效果如下图 最后一行的意思是正在监听本地的127.0.0.1的3000端口，说明程序没有出错此时在浏览器打开网址http://localhost:3000/
> > #### 注意> > > localhost指向127.0.0.1> > > 此时页面应该是这个样子的 ## 二、Hello Viz代码详解 从整体上来看，这块代码主要分为3个部分，分别是导入组件，处理index请求和主程序### 导入组件首先导入了SocketAddr，用来表示socket地址，然后导入了Viz的一些组件* Request 请求* Result 响应* Router 路由* Server 服务器* ServiceMaker 服务### 处理请求这里使用异步函数来实现index的处理，传入Request，这个过程系统会自动为我们处理。然后响应的是字符串类型，在函数体中返回了字符串“Hello Viz”### 主函数在Viz中，主函数也是异步函数，使用addr表示本地地址和监听的端口，然后挂载Router，使与index处理器相联系，再开启服务器。## 三、常见用法### 简单的处理程序async fn index(_: Request) -> Result {
Ok(Response::text(“Hello, World!”))
}
async fn about(_: Request) -> Result<&'static str> {
Ok(“About Me!”)
}
async fn not_found(_: Request) -> Result {
Ok(“Not Found!”)
}
### 实现处理程序特质#[derive(Clone)]
struct MyHandler {
code: Arc,
}
#[async_trait]
impl Handler for MyHandler {
type Output = Result;
async fn call(&self, req: Request) -> Self::Output { let path = req.path().clone(); let method = req.method().clone(); let code = self.code.fetch\_add(1, Ordering::SeqCst); Ok(format!("code = {}, method = {}, path = {}", code, method, path).into\_response())}}
### 路由传参Viz 允许更灵活地组织代码。async fn show_user(mut req: Request) -> Result {
let Params(id) = req.extract::<Params>().await?;
Ok(format!(“post {}”, id).into_response())
}
async fn show_user_ext(Params(id): Params) -> Result {
Ok(format!(“Hi, NO.{}”, id))
}
async fn show_user_wrap(req: Request) -> Result {
// https://github.com/rust-lang/rust/issues/48919
// show_user_ext.call(req).await
FnExt::call(&show_user_ext, req).await
}
let app = Router::new()
.get(“/users/:id”, show_user)
.get(“/users_wrap/:id”, show_user_wrap)
.get(“/users_ext/:id”, show_user_ext.into_handler());
### 链式组合程序HandlerExt是Handler的拓展特质，它提供了各种方便的组合函数。比如FutureExt和StreamExt特质。async fn index(_: Request) -> Result {
Ok(Response::text(“hyper”))
}
async fn before(req: Request) -> Result {
if req.method() == Method::POST {
Ok(req)
} else {
Err(StatusCode::METHOD_NOT_ALLOWED.into_error())
}
}
async fn around((req, handler): Next<Request, H>) -> Result
where
H: Handler<Request, Output = Result> + Clone,
{
// before …
let result = handler.call(req).await;
// after …
result
}
async fn after(result: Result) -> Result {
result.map(|mut res| {
*res.status_mut() = StatusCode::NO_CONTENT;
res
})
}
let routing = Router::new()
.get(“/”, index.before(before).around(around).after(after));
### 中间件Viz 的中间件和处理程序具有共同的Handler特质，因此它很容易实现和扩展中间件。我们可以将中间件添加到单个处理程序或所有处理程序。我们还可以在构造过程中使用Transform特质 trait 来包装内部处理程序。async fn index(_: Request) -> Result {
Ok(StatusCode::OK.into_response())
}
async fn not_found(_: Request) -> Result {
Ok(StatusCode::OK)
}
async fn show_user(Params(id): Params) -> Result {
Ok(format!(“post {}”, id))
}
// middleware fn
async fn around((req, handler): Next<Request, H>) -> Result
where
H: Handler<Request, Output = Result>,
{
// before …
let result = handler.call(req).await;
// after …
result
}
// middleware struct
#[derive(Clone)]
struct MyMiddleware {}
#[async_trait]
impl Handler<Next<Request, H>> for MyMiddleware
where
H: Handler,
{
type Output = H::Output;
async fn call(&self, (i, h): Next<Request, H>) -> Self::Output { h.call(i).await}}
// A configuration for Timeout Middleware
struct Timeout {
delay: Duration,
}
impl Timeout {
pub fn new(secs: u64) -> Self {
Self { delay: Duration::from_secs(secs) }
}
}
impl<H: Clone> Transform for Timeout {
type Output = TimeoutMiddleware;
fn transform(&self, h: H) -> Self::Output { TimeoutMiddleware(h, self.delay)}}
// Timeout Middleware
#[derive(Clone)]
struct TimeoutMiddleware(H, Duration);
#[async_trait]
impl Handler for TimeoutMiddleware
where
H: Handler + Clone,
{
type Output = H::Output;
async fn call(&self, req: Request) -> Self::Output { self.0.call(req).await}}
let app = Router::new()
.get(“/”, index
// handler level
.around(around)
.around(MyMiddleware {})
.with(Timeout::new(1))
)
.route(“/users/:id”, get(
show_user
.into_handler()
.map_into_response()
// handler level
.around(around)
.with(Timeout::new(0))
)
.post(
(|_| async { Ok(Response::text(“update”)) })
// handler level
.around(around)
.with(Timeout::new(0))
)
// route level
.with_handler(MyMiddleware {})
.with(Timeout::new(2))
)
.get(“/*”, not_found
.map_into_response()
// handler level
.around(around)
.around(MyMiddleware {})
)
// router level
.with_handler(around)
.with_handler(MyMiddleware {})
.with(Timeout::new(4));
### 参数接收器从Request中提取参数。struct Counter(u16);
#[async_trait]
impl FromRequest for Counter {
type Error = Infallible;
async fn extract(req: &mut Request) -> Result<Self, Self::Error> {
let c = get_query_param(req.query_string());
Ok(Counter©)
}
}
fn get_query_param(query: Option<&str>) -> u16 {
let query = query.unwrap_or(“”);
let q = if let Some(pos) = query.find(‘q’) {
query.split_at(pos + 2).1.parse().unwrap_or(1)
} else {
1
};
cmp::min(500, cmp::max(1, q))
}
### 路由识别URL和分配处理器。#### 一个简单的路由async fn index(_: Request) -> Result {
Ok(().into_response())
}
let root = Router::new()
.get(“/”, index)
.route(“/about”, get(|_| async { Ok(“about”) }));
let search = Router::new()
.route(“/”, Route::new().get(|_| async { Ok(“search”) }));
#### CRUD操作添加带请求方式的方法。async fn index_todos(_: Request) -> Result {
Ok(())
}
async fn create_todo(_: Request) -> Result<&'static str> {
Ok(“created”)
}
async fn new_todo(_: Request) -> Result {
Ok(Response::html(r#"
async fn show_todo(mut req: Request) -> Result {
let Params(id): Params = req.extract().await?;
Ok(Response::text(format!(“todo’s id is {}”, id)))
}
async fn update_todo(_: Request) -> Result<()> {
Ok(())
}
async fn destroy_todo(_: Request) -> Result<()> {
Ok(())
}
async fn edit_todo(_: Request) -> Result<()> {
Ok(())
}
let todos = Router::new()
.route(“/”, get(index_todos).post(create_todo))
.post(“/new”, new_todo)
.route(“/:id”, get(show_todo).patch(update_todo).delete(destroy_todo))
.get(“/:id/edit”, edit_todo);
### 资源// GET /search
async fn search_users(_: Request) -> Result {
Ok(Response::json::<Vec>(vec![])?)
}
// GET /
async fn index_users(_: Request) -> Result {
Ok(Response::json::<Vec>(vec![])?)
}
// GET /new
async fn new_user(_: Request) -> Result<&'static str> {
Ok(“User Form”)
}
// POST /
async fn create_user(_: Request) -> Result<&'static str> {
Ok(“Created User”)
}
// GET /user\_id
async fn show_user(_: Request) -> Result<&'static str> {
Ok(“User ID 007”)
}
// GET /user\_id/edit
async fn edit_user(_: Request) -> Result<&'static str> {
Ok(“Edit User Form”)
}
// PUT /user\_id
async fn update_user(_: Request) -> Result<&'static str> {
Ok(“Updated User”)
}
// DELETE /user\_id
async fn delete_user(_: Request) -> Result<&'static str> {
Ok(“Deleted User”)
}
let users = Resources::default()
.named(“user”)
.route(“/search”, get(search_users))
.index(index_users)
.new(new_user)
.create(create_user)
.show(show_user)
.edit(edit_user)
.update(update_user)
.destroy(delete_user);
---## 总结本期主要是对Rust的轻量级Web框架Viz进行了入门级的了解，并且给出了Viz官方的示例代码，包括中间件，响应处理，路由等组件的用法，可以看出Viz是个纯web框架，非常的简洁。在后续的文章中，将会陆续为大家介绍rust的数据库操作，json操作等相关技术，rust做web后端的相关技术补齐就开始项目实战。如果你对rust感兴趣，请关注本系列文章。