eventide-application

中文版本: README.zh.md

Application layer of the eventide DDD/CQRS toolkit. It orchestrates use cases and translates external requests (HTTP / CLI / job runner) into domain commands and queries without leaking infrastructure concerns.

What is in here

Type / module	Role
`CommandHandler<C>`	Handles a single command type with side effects (writes).
`QueryHandler<Q, R>`	Handles a single query type and returns a typed result `R`.
`CommandBus`	Type-erased dispatch. Routes a command to its registered handler by `TypeId`.
`QueryBus`	Same idea for queries, with a typed return value.
`InMemoryCommandBus` / `InMemoryQueryBus`	Concurrent reference implementations backed by `dashmap::DashMap`.
`AppContext`	Cross-cutting context: `EventContext` (correlation / causation / actor) + `idempotency_key`.
`AppError`	`Domain` / `Validation` / `Authorization` / `Infra` / `HandlerNotFound` / `AggregateNotFound` / `TypeMismatch`.

Add it

[dependencies]
eventide-application = "0.1"
async-trait = "0.1"
tokio = { version = "1", features = ["full"] }

Or via the umbrella crate (recommended), which re-exports tokio and async_trait so a single dependency is enough:

[dependencies]
eventide = "0.1"

When using the umbrella crate, write #[eventide::tokio::main] and use eventide::async_trait::async_trait; instead of depending on tokio / async-trait directly.

Command example

use async_trait::async_trait;
use eventide_application::command_bus::CommandBus;
use eventide_application::command_handler::CommandHandler;
use eventide_application::context::AppContext;
use eventide_application::InMemoryCommandBus;
use std::sync::Arc;

#[derive(Debug)]
struct CreateUser { name: String }

struct CreateUserHandler;

#[async_trait]
impl CommandHandler<CreateUser> for CreateUserHandler {
    async fn handle(
        &self,
        _ctx: &AppContext,
        _cmd: CreateUser,
    ) -> Result<(), eventide_application::error::AppError> {
        Ok(())
    }
}

#[tokio::main]
async fn main() {
    let bus = InMemoryCommandBus::new();
    bus.register::<CreateUser, _>(Arc::new(CreateUserHandler)).unwrap();

    bus.dispatch(&AppContext::default(), CreateUser { name: "Alice".into() })
        .await
        .unwrap();
}

Query example

use async_trait::async_trait;
use eventide_application::context::AppContext;
use eventide_application::query_bus::QueryBus;
use eventide_application::query_handler::QueryHandler;
use eventide_application::InMemoryQueryBus;
use serde::Serialize;
use std::sync::Arc;

#[derive(Debug)]
struct GetUser { id: u32 }

#[derive(Debug, Serialize)]
struct UserDto { id: u32, name: String }

struct GetUserHandler;

#[async_trait]
impl QueryHandler<GetUser, UserDto> for GetUserHandler {
    async fn handle(
        &self,
        _ctx: &AppContext,
        q: GetUser,
    ) -> Result<UserDto, eventide_application::error::AppError> {
        Ok(UserDto { id: q.id, name: "Alice".into() })
    }
}

#[tokio::main]
async fn main() {
    let bus = InMemoryQueryBus::new();
    bus.register::<GetUser, UserDto, _>(Arc::new(GetUserHandler)).unwrap();

    let _ = bus
        .dispatch::<GetUser, UserDto>(&AppContext::default(), GetUser { id: 1 })
        .await;
}

Concurrency notes

Bus registries use dashmap::DashMap. Handlers are wrapped in Arc and cloned out before dispatch, so locks never span an await.
AppError::HandlerNotFound(name) reports the missing handler with std::any::type_name::<T>(), keeping the message short and stable.
AppError::TypeMismatch is a defensive error used when the registry is unexpectedly mutated to hold the wrong handler type.

Run tests / examples

cargo build -p eventide-application
cargo test  -p eventide-application
cargo run   -p eventide-application --example inmemory_command_bus
cargo run   -p eventide-application --example inmemory_query_bus

Layered architecture

eventide-application  →  eventide-domain  ←  eventide-macros

Application code depends only on the domain layer. Concrete repositories, event stores, and message buses live in your own infrastructure crate and are wired into handlers through dependency injection.

License

Licensed under either of Apache-2.0 or MIT at your option.

eventide-application 0.1.1