4

我正在尝试创建一个 rust 的打印服务器，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：您只需要使用 Serde 库。

不幸的是，这对我来说并不那么简单......

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trait要这样做，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

*****:~/*****/label-printer-server-rust/server$ cargo run
   Compiling hello v0.0.0 (/home/*****/*****/label-printer-server-rust/server)
error[E0277]: the trait bound `rocket_contrib::json::Json<order_route::Printers>: Responder<'_, '_>` is not satisfied
   --> 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`
   --> /home/*****/.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> {
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

error[E0308]: mismatched types
  --> src/order_route.rs:27:10
   |
27 |     Json(resp)
   |          ^^^^ expected struct `order_route::Printers`, found enum `Result`
   |
   = note: expected struct `order_route::Printers`
                found enum `Result<structures::Printers, Box<dyn StdError>>`

Some errors have detailed explanations: E0277, E0308.
For more information about an error, try `rustc --explain E0277`.
error: could not compile `hello` due to 2 previous errors
4

3 回答 3

6

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Responder了，但它实现了ResponderRocket v4 的特性，而不是 Rocket v5 的特性。

在 Rocket v5 中，不再Json是其中的一部分rocket_contib，而是包含在rocketcrate 中（请注意，您需要json在 crate 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，您现在也可以rocket_contrib从 Cargo.toml 中删除（因为您没有使用其中的任何功能）。

于 2021-08-06T14:15:43.597 回答
1

任何觉得困难的人，这里是解决方案：

  • 在您的文件中为火箭锈启用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

    // 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
   }
}

  • 使用 cURL 测试 API

    curl -d '{"age": 12,"name":"John Doe"}' -H 'Content-Type: application/json' 
http://localhost:8000/post

# Response
# {"name":"John Doe","age":12}
于 2022-01-29T09:52:01.727 回答
0

我想添加到 Elias 的答案，评论中提到：

在您cargo.toml需要启用 JSON 功能：

[dependencies]
## SEE HERE!! 
rocket = {version ="0.5.0-rc.1", features=["json"]}

# other properties omitted for brevity 

# You can remove this!! Rocket Contrib doesn't exist in Rocket V0.5 
#[dependencies.rocket_contrib]
#version = "0.4.10"
#default-features = false
#features = ["json"]
于 2021-11-18T02:33:16.143 回答