cargo.toml

[package]
name = "webexample"
version = "0.1.0"
authors = ["ifukazoo <ifukazoo@gmail.com>"]
edition = "2018"

# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html

[dependencies]
tower-web = "*"
reqwest = { version = "0.10", features = ["blocking", "json"] }
serde = { version = "1.0", features = ["derive"] }
serde_json = "*"

main.rs

#[macro_use]
extern crate tower_web;
extern crate reqwest;
extern crate serde;

use reqwest::blocking;
use serde::{Deserialize, Serialize};
use tower_web::ServiceBuilder;

/// This type will be part of the web service as a resource.
#[derive(Clone, Debug)]
struct HelloWorld;

/// This will be the JSON response
#[derive(Response)]
struct HelloResponse {
    message: &'static str,
}
#[derive(Response)]
struct UserResponse {
    users: Vec<User>,
}

#[derive(Serialize, Deserialize, Clone)]
struct User {
    userId: i32,
    id: i32,
    title: String,
    body: String,
}

impl_web! {
    impl HelloWorld {
        #[get("/")]
        #[content_type("json")]
        fn hello_world(&self) -> Result<HelloResponse, ()> {
            Ok(HelloResponse {
                            message: "hello world",
            })
        }
        #[get("/user")]
        #[content_type("json")]
        fn get_user(&self) -> Result<UserResponse, ()> {
            let resp = reqwest::blocking::get("https://jsonplaceholder.typicode.com/posts?userId=1").unwrap();
            let json  = resp.json::<Vec<User>>().unwrap();
            let mut json = json.clone();
            for u in &mut json {
                u.id = 0xFF;

            }
            let serialized = serde_json::to_string(&json).unwrap();

            Ok(UserResponse {
                            users: json,
            })
        }
    }
}

pub fn main() {
    let addr = "127.0.0.1:8082".parse().expect("Invalid address");
    println!("Listening on http://{}", addr);

    ServiceBuilder::new()
        .resource(HelloWorld)
        .run(&addr)
        .unwrap();
}