如何使用 abonander/multipart 和 Rocket 解析多部分表单？

Question

I have no idea how you're meant to go about parsing a multipart form besides doing it manually using just the raw post-data string as input

我会尝试调整 the Hyper example，但如有任何帮助，我们将不胜感激。

相关问题：

Answer 1

Rocket 对数据的主要抽象是 FromData 特征。给定 POST 数据和请求，您可以构造给定类型：

pub trait FromData<'a>: Sized {
    type Error;
    type Owned: Borrow<Self::Borrowed>;
    type Borrowed: ?Sized;
    fn transform(
        request: &Request, 
        data: Data
    ) -> Transform<Outcome<Self::Owned, Self::Error>>;
    fn from_data(
        request: &Request, 
        outcome: Transformed<'a, Self>
    ) -> Outcome<Self, Self::Error>;
}

然后，只需读取 API for multipart 并将选项卡 A 插入插槽 B:

#![feature(proc_macro_hygiene, decl_macro)]

use multipart::server::Multipart; // 0.16.1, default-features = false, features = ["server"]
use rocket::{
    data::{Data, FromData, Outcome, Transform, Transformed},
    post, routes, Request,
}; // 0.4.2
use std::io::Read;

#[post("/", data = "<upload>")]
fn index(upload: DummyMultipart) -> String {
    format!("I read this: {:?}", upload)
}

#[derive(Debug)]
struct DummyMultipart {
    alpha: String,
    one: i32,
    file: Vec<u8>,
}

// All of the errors in these functions should be reported
impl<'a> FromData<'a> for DummyMultipart {
    type Owned = Vec<u8>;
    type Borrowed = [u8];
    type Error = ();

    fn transform(_request: &Request, data: Data) -> Transform<Outcome<Self::Owned, Self::Error>> {
        let mut d = Vec::new();
        data.stream_to(&mut d).expect("Unable to read");

        Transform::Owned(Outcome::Success(d))
    }

    fn from_data(request: &Request, outcome: Transformed<'a, Self>) -> Outcome<Self, Self::Error> {
        let d = outcome.owned()?;

        let ct = request
            .headers()
            .get_one("Content-Type")
            .expect("no content-type");
        let idx = ct.find("boundary=").expect("no boundary");
        let boundary = &ct[(idx + "boundary=".len())..];

        let mut mp = Multipart::with_body(&d[..], boundary);

        // Custom implementation parts

        let mut alpha = None;
        let mut one = None;
        let mut file = None;

        mp.foreach_entry(|mut entry| match &*entry.headers.name {
            "alpha" => {
                let mut t = String::new();
                entry.data.read_to_string(&mut t).expect("not text");
                alpha = Some(t);
            }
            "one" => {
                let mut t = String::new();
                entry.data.read_to_string(&mut t).expect("not text");
                let n = t.parse().expect("not number");
                one = Some(n);
            }
            "file" => {
                let mut d = Vec::new();
                entry.data.read_to_end(&mut d).expect("not file");
                file = Some(d);
            }
            other => panic!("No known key {}", other),
        })
        .expect("Unable to iterate");

        let v = DummyMultipart {
            alpha: alpha.expect("alpha not set"),
            one: one.expect("one not set"),
            file: file.expect("file not set"),
        };

        // End custom

        Outcome::Success(v)
    }
}

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

我从未真正使用过这些 API 中的任何一个，因此不能保证这是一个好的实现。事实上，所有对错误的恐慌肯定意味着它不是最优的。生产用途将干净利落地处理所有这些。

但是，它确实有效：

%curl -X POST -F alpha=omega -F one=2 -F file=@hello http://localhost:8000/
I read this: DummyMultipart { alpha: "omega", one: 2, file: [104, 101, 108, 108, 111, 44, 32, 119, 111, 114, 108, 100, 33, 10] }

高级实现将允许在特定于用户的数据和通用多部分方面之间进行一些抽象。像 Multipart<MyForm> 这样的东西会很好。

Rocket points out 的作者认为此解决方案允许恶意最终用户 POST 无限大小的文件，这将导致机器运行内存不足。根据预期用途，您可能希望对读取的字节数设置某种上限，可能会在某个断点处写入文件系统。

Answer 2

正式支持 Rocket 中的多部分表单解析 is still being discussed. Until then, take a look at the official example on how to integrate the multipart crate with Rocket: https://github.com/abonander/multipart/blob/master/examples/rocket.rs

如何使用 abonander/multipart 和 Rocket 解析多部分表单？

How to parse multipart forms using abonander/multipart with Rocket?

rust

rust-rocket