Rust: Rocket で Redis のデータを読む

Redis に次のようにデータが入っている時のデータを読みます。

$ redis-cli
127.0.0.1:6379> keys *
1) "t1857"
2) "t1859"
3) "t1855"
4) "t1853"
5) "t1858"
6) "t1854"
7) "t1856"
8) "t1851"
9) "t1852"
127.0.0.1:6379>

プロジェクトの作成

cargo new redis-cities --bin
cd redis-cities

次のファイルを作成します。

Cargo.toml

[package]
name = "backend"
version = "0.1.0"
edition = "2018"

[dependencies]
rocket = "0.4.5"

[dependencies.rocket_contrib]
version = "0.4.5"
default-features = false
features = ["redis_pool"]

Rocket.toml

[global.databases]
cities = { url = "redis://127.0.0.1:6379" }

src/main.rs

// --------------------------------------------------------------------
/*
    redis-cities/src/main.rs

                    Sep/20/2020
*/
// --------------------------------------------------------------------
#![feature(proc_macro_hygiene, decl_macro)]
#[macro_use] extern crate rocket;
#[macro_use] extern crate rocket_contrib;

use std::io::Cursor;

use rocket::request::Request;
use rocket::response::{self, Response, Responder};
use rocket::http::ContentType;

use rocket_contrib::databases::redis::{self, Commands};

// --------------------------------------------------------------------
#[database("cities")]
struct CitiesDbConn(redis::Connection);

struct Cities {
  destination: String,
}

// --------------------------------------------------------------------
impl<'r> Responder<'r> for Cities {
  fn respond_to(self, _: &Request) -> response::Result<'r> {
    Response::build()
      .sized_body(Cursor::new(format!("{}", self.destination)))
      .header(ContentType::new("text", "plain"))
      .ok()
  }
}

// --------------------------------------------------------------------
#[get("/api/<id>")]
fn lookup(conn: CitiesDbConn, id: String) -> Option<Cities> {
    match conn.get(&id) {
    Ok(value) => Some(Cities {destination: value}),
    Err(_e) => None,
    }
}



// --------------------------------------------------------------------
fn main() {
  rocket::ignite()
  .attach(CitiesDbConn::fairing())
  .mount(
    "/",
    rocket::routes![lookup]
    )
  .launch();

}

// --------------------------------------------------------------------

コンパイル

cargo build

サーバーの実行

cargo run

テスト

$ curl http://localhost:8000/api/t1851
{"date_mod":"1956-6-9","name":"福井","population":53921}