rust

name	rust
description	Use when building Axum applications, implementing type-safe handlers, working with SQLx, setting up error handling with thiserror, or writing Rust backend services.
disable-model-invocation	true

Rust Backend Patterns

Overview

Rust patterns for building backend services with Axum.

Project Structure

project/
├── src/
│   ├── main.rs               # Entry point
│   ├── lib.rs                # Library root
│   ├── config.rs             # Configuration
│   ├── error.rs              # Error types
│   ├── routes/               # Route handlers
│   │   ├── mod.rs
│   │   └── users.rs
│   ├── services/             # Business logic
│   ├── repositories/         # Data access
│   ├── models/               # Domain models
│   └── middleware/           # HTTP middleware
├── migrations/               # SQLx migrations
├── tests/                    # Integration tests
├── Cargo.toml
└── .env

Axum Application

Main Application

// src/main.rs
use axum::{
    routing::{get, post},
    Router,
};
use sqlx::postgres::PgPoolOptions;
use std::sync::Arc;
use tower_http::cors::CorsLayer;

mod config;
mod error;
mod routes;
mod services;
mod repositories;

use config::Config;

#[derive(Clone)]
pub struct AppState {
    pub db: sqlx::PgPool,
    pub config: Arc<Config>,
}

#[tokio::main]
async fn main() -> Result<(), Box<dyn std::error::Error>> {
    dotenvy::dotenv().ok();
    tracing_subscriber::init();

    let config = Config::from_env()?;

    let pool = PgPoolOptions::new()
        .max_connections(config.database.max_connections)
        .connect(&config.database.url)
        .await?;

    sqlx::migrate!().run(&pool).await?;

    let state = AppState {
        db: pool,
        config: Arc::new(config),
    };

    let app = Router::new()
        .route("/health", get(|| async { "ok" }))
        .nest("/api/users", routes::users::router())
        .with_state(state)
        .layer(CorsLayer::permissive());

    let listener = tokio::net::TcpListener::bind("0.0.0.0:3000").await?;
    tracing::info!("listening on {}", listener.local_addr()?);
    axum::serve(listener, app).await?;

    Ok(())
}

Configuration

// src/config.rs
use serde::Deserialize;

#[derive(Debug, Deserialize)]
pub struct Config {
    pub database: DatabaseConfig,
    pub jwt: JwtConfig,
}

#[derive(Debug, Deserialize)]
pub struct DatabaseConfig {
    pub url: String,
    #[serde(default = "default_max_connections")]
    pub max_connections: u32,
}

#[derive(Debug, Deserialize)]
pub struct JwtConfig {
    pub secret: String,
    #[serde(default = "default_expiry")]
    pub expiry_hours: u64,
}

fn default_max_connections() -> u32 { 10 }
fn default_expiry() -> u64 { 24 }

impl Config {
    pub fn from_env() -> Result<Self, config::ConfigError> {
        config::Config::builder()
            .add_source(config::Environment::default().separator())
            .()?
            .()
    }
}

Error Handling

// src/error.rs
use axum::{
    http::StatusCode,
    response::{IntoResponse, Response},
    Json,
};
use serde_json::json;
use thiserror::Error;

#[derive(Error, Debug)]
pub enum AppError {
    #[error("Not found: {0}")]
    NotFound(String),

    #[error("Validation error: {0}")]
    Validation(String),

    #[error("Unauthorized")]
    Unauthorized,

    #[error("Forbidden")]
    Forbidden,

    #[error("Database error")]
    Database(#[from] sqlx::Error),

    #[error("Internal error")]
    Internal(#[from] anyhow::Error),
}

impl IntoResponse for AppError {
    fn into_response(self) -> Response {
        let (status, code, message) = match &self {
            AppError::NotFound(msg) => (StatusCode::NOT_FOUND, "NOT_FOUND", msg.clone()),
            AppError::Validation(msg) => (StatusCode::BAD_REQUEST, "VALIDATION_ERROR", msg.clone()),
            AppError::Unauthorized => (StatusCode::UNAUTHORIZED, , .()),
            AppError::Forbidden => (StatusCode::FORBIDDEN, , .()),
            AppError::(e) => {
                tracing::error!(, e);
                (StatusCode::INTERNAL_SERVER_ERROR, , .())
            }
            AppError::(e) => {
                tracing::error!(, e);
                (StatusCode::INTERNAL_SERVER_ERROR, , .())
            }
        };

        (
            status,
            (json!({
                : {
                    : code,
                    : message
                }
            })),
        ).()
    }
}

  <T> = std::result::<T, AppError>;

Models and DTOs

// src/models/user.rs
use chrono::{DateTime, Utc};
use serde::{Deserialize, Serialize};
use sqlx::FromRow;
use uuid::Uuid;
use validator::Validate;

#[derive(Debug, FromRow, Serialize)]
pub struct User {
    pub id: Uuid,
    pub name: String,
    pub email: String,
    #[serde(skip_serializing)]
    pub password_hash: String,
    pub created_at: DateTime<Utc>,
    pub updated_at: Option<DateTime<Utc>>,
}

#[derive(Debug, Deserialize, Validate)]
pub struct CreateUser {
    #[validate(length(min = 2, max = 100))]
    pub name: String,
    #[validate(email)]
    pub email: String,
    #[validate(length(min = 8))]
    pub password: String,
}

#[derive(Debug, Deserialize, Validate)]
pub struct UpdateUser {
    #[validate(length(min = 2, max = 100))]
    pub name: Option<String>,
    #[validate(email)]
    pub email: Option<String>,
}

#[derive(Debug, Serialize)]
pub struct  {
     id: Uuid,
     name: ,
     email: ,
     created_at: DateTime<Utc>,
}

 <User>   {
     (user: User)   {
         {
            id: user.id,
            name: user.name,
            email: user.email,
            created_at: user.created_at,
        }
    }
}

Repository Pattern

// src/repositories/user.rs
use sqlx::PgPool;
use uuid::Uuid;
use crate::error::{AppError, Result};
use crate::models::user::{User, CreateUser, UpdateUser};

pub struct UserRepository<'a> {
    pool: &'a PgPool,
}

impl<'a> UserRepository<'a> {
    pub fn new(pool: &'a PgPool) -> Self {
        Self { pool }
    }

    pub async fn find_by_id(&self, id: Uuid) -> Result<Option<User>> {
        sqlx::query_as!(User, "SELECT * FROM users WHERE id = $1", id)
            .fetch_optional(self.pool)
            .await
            .map_err(AppError::Database)
    }

    pub async fn find_by_email(&self, email: &str) -> Result<Option<User>> {
        sqlx::query_as!(User, "SELECT * FROM users WHERE email = $1", email)
            .fetch_optional(self.pool)
            .await
            .map_err(AppError::Database)
    }

       (&, limit: , offset: )  <<User>> {
        sqlx::query_as!(
            User,
            ,
            limit,
            offset
        )
        .(.pool)
        .
        .(AppError::Database)
    }

       (&, input: &CreateUser, password_hash: &)  <User> {
        sqlx::query_as!(
            User,
            ,
            input.name,
            input.email,
            password_hash
        )
        .(.pool)
        .
        .(AppError::Database)
    }

       (&, id: Uuid, input: &UpdateUser)  <<User>> {
        sqlx::query_as!(
            User,
            ,
            id,
            input.name,
            input.email
        )
        .(.pool)
        .
        .(AppError::Database)
    }

       (&, id: Uuid)  <> {
          = sqlx::query!(, id)
            .(.pool)
            .
            .(AppError::Database)?;

        (result.() > )
    }
}

Route Handlers

// src/routes/users.rs
use axum::{
    extract::{Path, Query, State},
    routing::{get, post, delete},
    Json, Router,
};
use uuid::Uuid;
use validator::Validate;

use crate::{
    error::{AppError, Result},
    models::user::{CreateUser, UpdateUser, UserResponse},
    repositories::user::UserRepository,
    services::user::UserService,
    AppState,
};

#[derive(Debug, serde::Deserialize)]
pub struct ListQuery {
    #[serde(default = "default_page")]
    page: i64,
    #[serde(default = "default_limit")]
    limit: i64,
}

fn default_page() -> i64 { 1 }
fn default_limit() -> i64 { 20 }

pub fn router() -> Router<AppState> {
    Router::new()
        .route("/", get(list_users).post(create_user))
        .route("/:id", get(get_user).patch(update_user).delete(delete_user))
}

async fn list_users(
    State(state): State<AppState>,
    Query(query): Query<ListQuery>,
)  <Json<<UserResponse>>> {
      = UserRepository::(&state.db);
      = (query.page - ) * query.limit;
      = repo.(query.limit, offset).?;
    ((users.().(::into).()))
}

  (
    (state): State<AppState>,
    (id): Path<Uuid>,
)  <Json<UserResponse>> {
      = UserRepository::(&state.db);
      = repo
        .(id)
        .?
        .(|| AppError::(.()))?;
    ((user.()))
}

  (
    (state): State<AppState>,
    (input): Json<CreateUser>,
)  <Json<UserResponse>> {
    input.().(|e| AppError::(e.()))?;

      = UserService::(&state.db);
      = service.(input).?;
    ((user.()))
}

  (
    (state): State<AppState>,
    (id): Path<Uuid>,
    (input): Json<UpdateUser>,
)  <Json<UserResponse>> {
    input.().(|e| AppError::(e.()))?;

      = UserRepository::(&state.db);
      = repo
        .(id, &input)
        .?
        .(|| AppError::(.()))?;
    ((user.()))
}

  (
    (state): State<AppState>,
    (id): Path<Uuid>,
)  <()> {
      = UserRepository::(&state.db);
     !repo.(id).? {
         (AppError::(.()));
    }
    (())
}

Testing

// tests/users.rs
use axum::{
    body::Body,
    http::{Request, StatusCode},
};
use tower::ServiceExt;
use serde_json::json;

#[tokio::test]
async fn test_list_users() {
    let app = create_test_app().await;

    let response = app
        .oneshot(
            Request::builder()
                .uri("/api/users")
                .body(Body::empty())
                .unwrap(),
        )
        .await
        .unwrap();

    assert_eq!(response.status(), StatusCode::OK);
}

#[tokio::test]
async fn test_create_user() {
    let app = create_test_app().await;

    let response = app
        .oneshot(
            Request::builder()
                .method("POST")
                .uri("/api/users")
                .header("content-type", "application/json")
                .(Body::(
                    serde_json::(&json!({
                        : ,
                        : ,
                        : 
                    }))
                    .(),
                ))
                .(),
        )
        .
        .();

    (response.(), StatusCode::OK);
}

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Rust Axum patterns for backend development