An issue with routing errors after adding status to the axum program

[jing-951]

I encountered an issue where a processing function registered in the router would report an error when obtaining parameters from a request after adding state to the program. This error requires the processing function to implement a handler<_, _>, which confused me a lot. I tried to solve it, but I was unable to do so.

# This is my dependency
axum = "0.7.5"
serde = {version = "1.0.203",features = ["derive"]}
serde_json = "1.0.117"
sqlx = {version = "0.7.4",features = ["runtime-tokio","postgres"]}
tokio = {version = "1.38.0",features = ["full"]}

# This is my testing program

use std::time::Duration;
use sqlx::postgres::PgPoolOptions;
use axum::{
    Router,
    routing::{get,post},
    Json,
    extract::State,
    response::IntoResponse
};
use serde::Deserialize;

#[derive(Debug,Clone)]
pub struct AppState{
    pub db:sqlx::PgPool,
}


#[tokio::main]
async fn main(){
    let db_connection_str = "postgres://obj:123456@localhost:5432/objects_store"
    .to_string();

    let pool = PgPoolOptions::new()
        .max_connections(10)
        .acquire_timeout(Duration::from_secs(3))
        .connect(&db_connection_str)
        .await
        .expect("Database connection failed");


    let app = Router::new()
    .route("/", get(||async {"Hello world!"}))
    .route("/login", post(login))
    .with_state(pool);

    let listener = tokio::net::TcpListener::bind("0.0.0.0:3000")
    .await.unwrap();


    axum::serve(listener, app).await.unwrap();
}

#[derive(Debug,Deserialize)]
struct Loginfo{
    name:String,
    pwd:String,
}

pub async fn login(
    Json(req):Json<Loginfo>,
    State(pool):State<AppState>
)->impl IntoResponse{
    println!("{}",req.name);
    println!("{}",req.pwd);
    let row = sqlx::query("select * from t_user where id = 0")
        .fetch_one(&pool.db)
        .await;
    match row{
        Ok(_) => "aaaaa".to_string(),
        Err(e) => e.to_string(),
    }
}

# This is an error message

PS E:\code\test\axum_state_test> cargo run
   Compiling axum_state_test v0.1.0 (E:\code\test\axum_state_test)
error[E0277]: the trait bound `fn(axum::Json<Loginfo>, State<AppState>) -> impl Future<Output = impl IntoResponse> {login}: Handler<_, _>` is not satisfied
   --> src\main.rs:33:27
    |
33  |     .route("/login", post(login))
    |                      ---- ^^^^^ the trait `Handler<_, _>` is not implemented for fn item `fn(axum::Json<Loginfo>, State<AppState>) -> impl Future<Output = impl IntoResponse> {login}`
    |                      |
    |                      required by a bound introduced by this call
    |
    = help: the following other types implement trait `Handler<T, S>`:
              <Layered<L, H, T, S> as Handler<T, S>>
              <MethodRouter<S> as Handler<(), S>>
note: required by a bound in `post`
   --> D:\soft_install\dev_env\rust\.cargo\registry\src\mirrors.ustc.edu.cn-61ef6e0cd06fb9b8\axum-0.7.5\src\routing\method_routing.rs:389:1
    |
389 | top_level_handler_fn!(post, POST);
    | ^^^^^^^^^^^^^^^^^^^^^^----^^^^^^^
    | |                     |
    | |                     required by a bound in this function
    | required by this bound in `post`
    = note: this error originates in the macro `top_level_handler_fn` (in Nightly builds, run with -Z macro-backtrace for more info)

For more information about this error, try `rustc --explain E0277`.
error: could not compile `axum_state_test` (bin "axum_state_test") due to 1 previous error
PS E:\code\test\axum_state_test> 

[mladedav]

Try decorating your handler with #[debug_handler], it should provide better errors.

One thing that strikes me is that you're calling with_state(pool) where pool doesn't seem to be AppState.

[jing-951]

Thank you very much for your answer. I have tried writing AppState to with_sate (AppState) and adding # [debug_handler] to the handler. The compiler told me that the Json parameter of the handler should use axum:: extract:: Json. I think I used axum:: Json before, which is why this issue occurred.