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120 lines
3.6 KiB
Markdown
120 lines
3.6 KiB
Markdown
---
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title: 数据库
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menu: docs_patterns
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weight: 1010
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---
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# Diesel
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目前，Diesel 1.0不支持异步操作，但可以将actix同步actor系统用作数据库接口API。从技术上讲，同步actor是worker风格的actor。
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多个同步actors可以并行运行并处理来自同一队列的消息。同步actors以mpsc模式工作。
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我们来创建一个简单的数据库api，它可以将一个新的 user row插入到SQLite表中。我们必须定义一个同步actor和该actor将使用的连接。其他数据库可以使用相同的方法。
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```rust
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use actix::prelude::*;
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struct DbExecutor(SqliteConnection);
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impl Actor for DbExecutor {
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type Context = SyncContext<Self>;
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}
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```
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这是我们actor的定义。现在，我们必须定义创建用户消息和响应。
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```rust
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struct CreateUser {
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name: String,
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}
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impl Message for CreateUser {
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type Result = Result<User, Error>;
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}
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```
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我们可以向演员发送`CreateUser`消息`DbExecutor` actor，因此我们将收到一个 `User`实例。接下来，我们必须为此消息定义处理程序实现。
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```rust
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impl Handler<CreateUser> for DbExecutor {
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type Result = Result<User, Error>;
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fn handle(&mut self, msg: CreateUser, _: &mut Self::Context) -> Self::Result
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{
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use self::schema::users::dsl::*;
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// Create insertion model
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let uuid = format!("{}", uuid::Uuid::new_v4());
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let new_user = models::NewUser {
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id: &uuid,
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name: &msg.name,
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};
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// normal diesel operations
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diesel::insert_into(users)
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.values(&new_user)
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.execute(&self.0)
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.expect("Error inserting person");
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let mut items = users
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.filter(id.eq(&uuid))
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.load::<models::User>(&self.0)
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.expect("Error loading person");
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Ok(items.pop().unwrap())
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}
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}
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```
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仅此而已！现在，我们可以使用来在于任何http处理程序或中间件的DbExecutor actor。我们需要的只是启动DbExecutor actors并将地址存储在http处理程序可以访问的状态中。
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```rust
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/// This is state where we will store *DbExecutor* address.
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struct State {
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db: Addr<Syn, DbExecutor>,
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}
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fn main() {
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let sys = actix::System::new("diesel-example");
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// Start 3 parallel db executors
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let addr = SyncArbiter::start(3, || {
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DbExecutor(SqliteConnection::establish("test.db").unwrap())
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});
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// Start http server
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HttpServer::new(move || {
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App::with_state(State{db: addr.clone()})
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.resource("/{name}", |r| r.method(Method::GET).a(index))})
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.bind("127.0.0.1:8080").unwrap()
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.start().unwrap();
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println!("Started http server: 127.0.0.1:8080");
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let _ = sys.run();
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}
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```
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我们将在请求处理程序中使用该地址。处理程序返回future对象; 因此，我们异步接收响应消息。`Route::a()`必须用于异步处理注册。
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```rust
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/// Async handler
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fn index(req: HttpRequest<State>) -> Box<Future<Item=HttpResponse, Error=Error>> {
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let name = &req.match_info()["name"];
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// Send message to `DbExecutor` actor
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req.state().db.send(CreateUser{name: name.to_owned()})
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.from_err()
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.and_then(|res| {
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match res {
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Ok(user) => Ok(HttpResponse::Ok().json(user)),
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Err(_) => Ok(HttpResponse::InternalServerError().into())
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}
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})
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.responder()
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}
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```
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[diesel directory](https://github.com/actix/examples/tree/master/diesel/)提供了一个完整的示例。
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有关同步actors的更多信息可以在[actix documentation](https://docs.rs/actix/0.5.0/actix/sync/index.html)文档中找到 。
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