在Rocket中返回JAN，其状态不是200

Question

我希望我的Rocket API有这样的路由：

#[post("create/thing", format = "application/json", data="<thing>")]

当客户端发送{ "name": "mything" }时，一切都应该没问题，我知道如何做到这一点，但是当它发送{ "name": "foo" }时它应该响应这样的事情：

HTTP/1.1 422 Unprocessable Entity
Content-Type: application/json

{
  "errors": [
    {
      "status": "422",
      "title":  "Invalid thing name",
      "detail": "The name for a thing must be at least 4 characters long."
    }
  ]
}

如何在Rocket中使用JSON对象和不同于200的HTTP状态代码等结果进行响应？

这是我到目前为止所尝试的：

• impl FromRequest为我的Thing类型。这让我可以选择一个状态代码，因为我可以编写自己的from_request函数，但我无法返回任何其他内容。
• 在this example中注册错误捕获器，但这样我只能在没有上下文的情况下对一个HTTP状态代码做出反应。我有太多的失败模式为每个模式保留一个HTTP状态代码。

Answer 1

你需要建立一个响应。看看ResponseBuilder。您的回答可能看起来像这样。

use std::io::Cursor;
use rocket::response::Response;
use rocket::http::{Status, ContentType};

let response = Response::build()
    .status(Status::UnprocessableEntity)
    .header(ContentType::Json)
    .sized_body(Cursor::new("Your json body"))
    .finalize();

Answer 2

在@ hellow的帮助下，我明白了。解决方案是为新结构Responder实现ApiResponse特性，其中包含状态代码以及Json。这样我就可以完全按照自己的意愿行事：

#[post("/create/thing", format = "application/json", data = "<thing>")]
fn put(thing: Json<Thing>) -> ApiResponse {
    let thing: Thing = thing.into_inner();
    match thing.name.len() {
        0...3 => ApiResponse {
            json: json!({"error": {"short": "Invalid Name", "long": "A thing must have a name that is at least 3 characters long"}}),
            status: Status::UnprocessableEntity,
        },
        _ => ApiResponse {
            json: json!({"status": "success"}),
            status: Status::Ok,
        },
    }
}

这是完整的代码：

#![feature(proc_macro_hygiene)]
#![feature(decl_macro)]

#[macro_use]
extern crate rocket;
#[macro_use]
extern crate rocket_contrib;
extern crate serde;
#[macro_use]
extern crate serde_derive;
extern crate serde_json;

use rocket::http::{ContentType, Status};
use rocket::request::Request;
use rocket::response;
use rocket::response::{Responder, Response};
use rocket_contrib::json::{Json, JsonValue};

#[derive(Serialize, Deserialize, Debug)]
pub struct Thing {
    pub name: String,
}

#[derive(Debug)]
struct ApiResponse {
    json: JsonValue,
    status: Status,
}

impl<'r> Responder<'r> for ApiResponse {
    fn respond_to(self, req: &Request) -> response::Result<'r> {
        Response::build_from(self.json.respond_to(&req).unwrap())
            .status(self.status)
            .header(ContentType::JSON)
            .ok()
    }
}

#[post("/create/thing", format = "application/json", data = "<thing>")]
fn put(thing: Json<Thing>) -> ApiResponse {
    let thing: Thing = thing.into_inner();
    match thing.name.len() {
        0...3 => ApiResponse {
            json: json!({"error": {"short": "Invalid Name", "long": "A thing must have a name that is at least 3 characters long"}}),
            status: Status::UnprocessableEntity,
        },
        _ => ApiResponse {
            json: json!({"status": "success"}),
            status: Status::Ok,
        },
    }
}

fn main() {
    rocket::ignite().mount("/", routes![put]).launch();
}