前言

Viz，是个基于RUst的，快速、健壮、灵活、轻量级的 Web 框架。

特点

• 安全，禁止不安全代码
• 轻量
• 简单 + 灵活的处理器和中间件
• 链式操作
• 强大的Routing路由

一、Hello Viz

1. 创建项目

正如学习编程语言一样，我们先从官方入门案例学起，首先我们创建一个新项目

cargo new viz_hello

然后使用vscode打开

2. 引入viz

在Cargo.toml中写入，如下图

tokio = { version = "1.20.1", features = ["full"] }
viz = "0.3.1"

然后使用build来下载依赖

cargo build

安装完成

3. 运行Hello Viz

复制以下代码到main.rs，

use std::net::SocketAddr;
use viz::{Request, Result, Router, Server, ServiceMaker};
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<Response> {
    Ok(Response::text("Hello, World!"))
}
async fn about(_: Request) -> Result<&'static str> {
    Ok("About Me!")
}
async fn not_found(_: Request) -> Result<impl IntoResponse> {
    Ok("Not Found!")
}

实现处理程序特质

#[derive(Clone)]
struct MyHandler {
    code: Arc<AtomicUsize>,
}
#[async_trait]
impl Handler<Request> for MyHandler {
    type Output = Result<Response>;  
    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<Response> {
    let Params(id)  = req.extract::<Params<u64>>().await?;
    Ok(format!("post {}", id).into_response())
}
async fn show_user_ext(Params(id): Params<u64>) -> Result<impl IntoResponse> {
    Ok(format!("Hi, NO.{}", id))
}
async fn show_user_wrap(req: Request) -> Result<impl IntoResponse> {
    // 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<Response> {
    Ok(Response::text("hyper"))
}
async fn before(req: Request) -> Result<Request> {
    if req.method() == Method::POST {
        Ok(req)
    } else {
        Err(StatusCode::METHOD_NOT_ALLOWED.into_error())
    }
}
async fn around<H>((req, handler): Next<Request, H>) -> Result<Response>
where
    H: Handler<Request, Output = Result<Response>> + Clone,
{
    // before ...
    let result = handler.call(req).await;
    // after ...
    result
}
async fn after(result: Result<Response>) -> Result<Response> {
    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<Response> {
    Ok(StatusCode::OK.into_response())
}
async fn not_found(_: Request) -> Result<impl IntoResponse> {
    Ok(StatusCode::OK)
}
async fn show_user(Params(id): Params<u64>) -> Result<impl IntoResponse> {
    Ok(format!("post {}", id))
}
// middleware fn
async fn around<H>((req, handler): Next<Request, H>) -> Result<Response>
where
    H: Handler<Request, Output = Result<Response>>,
{
    // before ...
    let result = handler.call(req).await;
    // after ...
    result
}
// middleware struct
#[derive(Clone)]
struct MyMiddleware {}
#[async_trait]
impl<H> Handler<Next<Request, H>> for MyMiddleware
where
    H: Handler<Request>,
{
    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<H> for Timeout {
    type Output = TimeoutMiddleware<H>;
    fn transform(&self, h: H) -> Self::Output {
        TimeoutMiddleware(h, self.delay)
    }
}
// Timeout Middleware
#[derive(Clone)]
struct TimeoutMiddleware<H>(H, Duration);
#[async_trait]
impl<H> Handler<Request> for TimeoutMiddleware<H>
where
    H: Handler<Request> + 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(c))
    }
}
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<Response> {
    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<impl IntoResponse> {
    Ok(())
}
async fn create_todo(_: Request) -> Result<&'static str> {
    Ok("created")
}
async fn new_todo(_: Request) -> Result<Response> {
    Ok(Response::html(r#"
        <form method="post" action="/">
            <input name="todo" />
            <button type="submit">Create</button>
        </form>
    "#))
}
async fn show_todo(mut req: Request) -> Result<Response> {
    let Params(id): Params<u64> = 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<Response> {
    Ok(Response::json::<Vec<u64>>(vec![])?)
}
// GET `/`
async fn index_users(_: Request) -> Result<Response> {
    Ok(Response::json::<Vec<u64>>(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。