Share session information to iron handler

Question

I'm trying to implement a web API using Iron as a practical exercise. My session is the following struct, which will be encoded as a JWT. Every time I receive requests from clients, some handlers will need to access user_id;

#[derive(Serialize, Deserialize)]
struct Session {
    session_id: i32,
    user_id: Option<i32>,
    expiration: u64,
}

There are several ways to do this, but I don't know the most idiomatic and least verbose. I was thinking something like:

fn handle(&self, req: &mut Request) -> IronResult<Response> {
    let session = match get_session(req) {
        Err(err) => return Ok(Response::with((status::BadRequest, err.description()))),
        Ok(session) => session,
    };
    Ok(Response::with((status::Ok, err.description())))
}

But this way I'll need this snippet on several endpoints.

I could use a middleware, but I don't know how to catch the struct value between middlewares.

Answer 1

I ended up using a wrapper:

pub trait SessionHandler {
    fn session_manager(&self) -> &SessionManager;
    fn authenticated(&self) -> bool {
        false
    }
    fn handle_session(&self, session: &mut Session, req: &mut Request) -> IronResult<Response>;

    fn handle(&self, req: &mut Request) -> IronResult<Response> {
        let mut session = match self.session_manager().get_request_session(req) {
            None => return Ok(Response::with((status::Unauthorized, ""))),
            Some(session) => {
                if self.authenticated() {
                    if let None = session.user_id {
                        return Ok(Response::with((status::Forbidden, "")));
                    }
                }
                session
            }
        };
        self.handle_session(&mut session, req)
    }
}

pub struct SessionHandlerBox<T> {
    pub s: T
}

impl <T> Handler for SessionHandlerBox<T> where T: SessionHandler +  Send + Sync + 'static {
    fn handle(&self, r: &mut Request) -> IronResult<Response> {
        self.s.handle(r)
    }
}

So I use:

struct FileDelete {
    db: Arc<Pool<PostgresConnectionManager>>,
    sm: Arc<SessionManager>,
}

impl SessionHandler for FileDelete {
    fn session_manager(&self) -> &SessionManager {
        self.sm.as_ref()
    }
    fn handle_session(&self, session: &mut Session, req: &mut Request) -> IronResult<Response> {
        Ok(Response::with((status::Ok, "")))
    }
}

There's still boilerplate, but there's less "business logic". Any better solutions are welcome.

usage example:

 pub fn register_handlers<'s>(db: Pool<PostgresConnectionManager>, r: &'s mut Router, sm : Arc<SessionManager>) {
    let file_delete = FileDelete { db: Arc::new(db), sm: sm.clone() };
    r.delete("/file", SessionHandlerBox {s: file_delete}, "file_delete");
}