如何使用自动字段反序列化在 Rust Rocket 中返回 JSON 作为响应？

Question

我正在尝试使用 Rust 创建打印服务器，并在尝试发送 JSON 作为响应时遇到问题。

我在 Rocket 文档中发现发送 JSON 作为响应非常容易：您只需使用 Serde 库即可。

不幸的是，这对我来说并不是那么简单......

这是我当前的代码：

#[derive(Serialize,Deserialize)]
pub struct Printers {
    pub printers: Vec<Printer>,
}

#[derive(Serialize,Deserialize)]
pub struct Printer {
    pub device_type: String,
    pub uid: String,
    pub provider: String,
    pub name: String,
    pub connection: String,
    pub version: u8,
    pub manufacturer: String,
}

/**
 * Here is my main problem 
 *   -> I want to send back the Printers Object as a JSON
 */
#[get("/printers")]
fn printers(key: ApiKey<'_>) -> Json<Printers> {
    let resp = crate::get_printers::get();
    Json(resp)
}

这是错误代码：

   --> src/order_route.rs:25:33
    |
25  | fn printers(key: ApiKey<'_>) -> Json<Printers> {
    |                                 ^^^^^^^^^^^^^^ the trait `Responder<'_, '_>` is not implemented for `rocket_contrib::json::Json<order_route::Printers>`
    |
note: required by `route::handler::<impl Outcome<rocket::Response<'o>, Status, rocket::Data<'o>>>::from`
   --> ********/.cargo/registry/src/github.com-1ecc6299db9ec823/rocket-0.5.0-rc.1/src/route/handler.rs:188:5
    |
188 |     pub fn from<R: Responder<'r, 'o>>(req: &'r Request<'_>, responder: R) -> Outcome<'r> {
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

看来我需要一个trait来做到这一点，但不知道如何创建它，如果有人可以帮助我找到解决方案，我将不胜感激。

[编辑]

这是 Cargo.toml 文件

[package]
name = "test"
version = "0.0.0"
edition = "2018"
[dependencies]
rocket = "0.5.0-rc.1"
reqwest = { version = "0.11", features = ["blocking", "json"] }
openssl = { version = "0.10", features = ["vendored"] }
json = "0.12.4"
serde = "1.0.127"
serde_json = "1.0.66"

[dependencies.rocket_contrib]
version = "0.4.10"
default-features = false
features = ["json"]

[workspace]
members = [
    ""
]

这是完整的堆栈跟踪

[package]
name = "test"
version = "0.0.0"
edition = "2018"
[dependencies]
rocket = "0.5.0-rc.1"
reqwest = { version = "0.11", features = ["blocking", "json"] }
openssl = { version = "0.10", features = ["vendored"] }
json = "0.12.4"
serde = "1.0.127"
serde_json = "1.0.66"

[dependencies.rocket_contrib]
version = "0.4.10"
default-features = false
features = ["json"]

[workspace]
members = [
    ""
]

Answer 1

您正在使用 Rocket 0.5.0-rc.1 和 Rocket_contrib 0.4.10。虽然Jsonfrom Rocket_contrib确实实现了Responder，但它实现了ResponderRocket v4 的特征，而不是 Rocket v5 的特征。

在 Rocket v5 中，Json不再是其中的一部分rocket_contib，而是包含在rocketcrate 中（请注意，您需要在 cratejson上启用该功能rocket）：

use rocket::serde::json::Json;
use serde::{Serialize, Deserialize};

#[derive(Serialize, Deserialize)]
pub struct Printers {
    pub printers: Vec<Printer>,
}

#[derive(Serialize, Deserialize)]
pub struct Printer {
    pub device_type: String,
    pub uid: String,
    pub provider: String,
    pub name: String,
    pub connection: String,
    pub version: u8,
    pub manufacturer: String,
}

#[get("/printers")]
fn printers() -> Json<Printers> {
    todo!();
}

请注意，您现在还可以rocket_contrib从 Cargo.toml 中删除（因为您没有使用其中的任何功能）。

Answer 2

任何觉得困难的人，这里有解决方案：

• 在文件中启用Rocket Rust 的JSON功能Cargo.toml

  [package]
  #...
  
  [dependencies.rocket]
  version = "0.5.0-rc.1"
  features = ["json"]
  
  [dependencies.serde]
  version = "1.0.136"
  features = ["derive"]
  
  [dependencies]
  #...
  
  # rocket_contrib not required anymore
  

• 在你的src/main.rs文件中

  [package]
  #...
  
  [dependencies.rocket]
  version = "0.5.0-rc.1"
  features = ["json"]
  
  [dependencies.serde]
  version = "1.0.136"
  features = ["derive"]
  
  [dependencies]
  #...
  
  # rocket_contrib not required anymore
  

• 使用 cURL 测试 API

  // rocket v0.5.0-rc.1
  use rocket::{
     self,
     serde::{json::Json, Deserialize, Serialize},
  };
  
  #[derive(Deserialize, Serialize)]
  struct User {
     name: String,
     age: u8,
  }
  
  #[rocket::post("/post", format = "json", data = "<user>")]
  fn post_data(user: Json<User>) -> Json<User> {
     let name: String = user.name.clone();
     let age: u8 = user.age.clone();
  
     Json(User { name, age })
  }
  
  #[rocket::main]
  async fn main() {
     if let Err(err) = rocket::build()
        .mount("/", rocket::routes![post_data])
        .launch()
        .await
     {
        println!("Rocket Rust couldn't take off successfully!");
        drop(err); // Drop initiates Rocket-formatted panic
     }
  }