如何将 Trait 作为应用程序数据传递给 Actix Web？

Question

我想创建一个actix-web 服务器，我可以在其中提供我的Search 特征作为应用程序数据，以便在多个实现之间轻松交换或使用模拟实现进行测试。无论我尝试什么，我都无法编译它，或者当我编译它时，在 Web 浏览器中访问路由时出现以下错误：

App数据未配置，配置使用App::data()

这是我目前所拥有的

// main.rs

use actix_web::dev::Server;
use actix_web::{get, web, App, HttpServer, Responder};

pub trait Search {
    fn search(&self, query: &str) -> String;
}

#[derive(Clone)]
pub struct SearchClient {
    base_url: String,
}

impl SearchClient {
    pub fn new() -> Self {
        Self {
            base_url: String::from("/search"),
        }
    }
}

impl Search for SearchClient {
    fn search(&self, query: &str) -> String {
        format!("Searching in SearchClient: {}", query)
    }
}

#[get("/{query}")]
async fn index(
    web::Path(query): web::Path<String>,
    search: web::Data<dyn Search>,
) -> impl Responder {
    search.into_inner().search(&query)
}

pub fn create_server(
    search: impl Search + Send + Sync + 'static + Clone,
) -> Result<Server, std::io::Error> {
    let server = HttpServer::new(move || App::new().data(search.clone()).service(index))
        .bind("127.0.0.1:8080")?
        .run();
    Ok(server)
}

#[actix_web::main]
async fn main() -> std::io::Result<()> {
    let search_client = SearchClient::new();
    create_server(search_client).unwrap().await
}

#[cfg(test)]
mod tests {
    use super::*;

    #[derive(Clone)]
    pub struct TestClient;

    impl Search for TestClient {
        fn search(&self, query: &str) -> String {
            format!("Searching in TestClient: {}", query)
        }
    }

    #[actix_rt::test]
    async fn test_search() {
        let search_client = TestClient {};
        let server = create_server(search_client).unwrap();
        tokio::spawn(server);
    }
}

# Cargo.toml

[package]
name = "actix-trait"
version = "0.1.0"
edition = "2018"

[dependencies]
actix-rt = "1.1.1"
actix-web = "3.3.2"

[dev-dependencies]
tokio = "0.2.22"

Answer 1

将data 添加到您的App 时，您必须指定您希望它被向下转换为特征对象。 Data 不直接接受 unsized 类型，所以你必须先创建一个 Arc (which does accept unsized types) 然后将其转换为 Data。我们将使用app_data 方法来避免将搜索器包裹在双弧中。

pub fn create_server(
    search: impl Search + Send + Sync + 'static,
) -> Result<Server, std::io::Error> {
    let search: Data<dyn Search> = Data::from(Arc::new(search));
    
    HttpServer::new(move || {
        App::new()
            .app_data(search.clone())
    })
}

async fn index(
    query: Path<String>,
    search: Data<dyn Search>,
) -> impl Responder {     
    search.into_inner().search(&*query)
}

另一种方法是使用泛型。您的处理程序和 create_server 函数将比 Search 实现通用：

async fn index<T: Search>(
    web::Path(query): web::Path<String>,
    search: web::Data<T>,
-> impl Responder {
    search.into_inner().search(&query)
}

pub fn create_server<T: Search + Send + Sync + 'static + Clone>(
    search: T,
) -> Result<Server, std::io::Error> {
    let server = HttpServer::new(move || {
        App::new()
            .data(search.clone())
            .route("/{query}", web::get().to(index::<T>))
    })
    .bind("127.0.0.1:8080")?
    .run();
    Ok(server)
}

现在，当您在main 中创建服务器时，您可以使用SearchClient：

#[actix_web::main]
async fn main() -> std::io::Result<()> {
     let search_client = SearchClient::new();
     create_server(search_client).unwrap().await
}

当您为测试目的创建服务器时，您可以使用TestClient:

#[actix_rt::test]
async fn test_search() {
    let search_client = TestClient {};
    let server = create_server(search_client).unwrap();
}

基于泛型的方法的缺点是您不能使用#[get("")] 宏进行路由，因为您必须指定处理程序的泛型参数：

App::new()
    .route("/{query}", web::get().to(index::<T>))