Application

Application 是 Vapor 中一个非常重要的类，负责管理各类基础组件（比如：Provider、Middleware、Database、Route 等等）。

Application 的部分源码如下

public final class Application {
    public var environment: Environment
    public let eventLoopGroupProvider: EventLoopGroupProvider
    public let eventLoopGroup: EventLoopGroup
    public var storage: Storage
    public private(set) var didShutdown: Bool
    public var logger: Logger
    var isBooted: Bool

    public init(
        _ environment: Environment = .development,
        _ eventLoopGroupProvider: EventLoopGroupProvider = .createNew
    ) {
        Backtrace.install()
        self.environment = environment
        self.eventLoopGroupProvider = eventLoopGroupProvider
        switch eventLoopGroupProvider {
        case .shared(let group):
            self.eventLoopGroup = group
        case .createNew:
            self.eventLoopGroup = MultiThreadedEventLoopGroup(numberOfThreads: System.coreCount)
        }
        self.locks = .init()
        self.didShutdown = false
        self.logger = .init(label: "codes.vapor.application")
        self.storage = .init(logger: self.logger)
        self.lifecycle = .init()
        self.isBooted = false
        self.core.initialize()
        self.caches.initialize()
        self.views.initialize()
        self.passwords.use(.bcrypt)
        self.sessions.initialize()
        self.sessions.use(.memory)
        self.responder.initialize()
        self.responder.use(.default)
        self.servers.initialize()
        self.servers.use(.http)
        self.clients.initialize()
        self.clients.use(.http)
        self.commands.use(self.servers.command, as: "serve", isDefault: true)
        self.commands.use(RoutesCommand(), as: "routes")
        DotEnvFile.load(for: environment, on: .shared(self.eventLoopGroup), fileio: self.fileio, logger: self.logger)
    }

    ......
}

extension Application: RoutesBuilder {
    public func add(_ route: Route) {
        self.routes.add(route)
    }
}

其中

• environment：主要用于存放程序当前运行环境相关的数据。
• routes：主要用于管理 API 路由。

接下来，我们来看下 Run 目录中的 main.swift 文件。

var env = try Environment.detect()
try LoggingSystem.bootstrap(from: &env)
let app = Application(env)
defer { app.shutdown() }
try configure(app)
try app.run()

还有 configure.swift 文件。

// Called before your application initializes.
public func configure(_ app: Application) throws {
    // Serves files from `Public/` directory
    // app.middleware.use(FileMiddleware(publicDirectory: app.directory.publicDirectory))

    // Configure SQLite database
    app.databases.use(.sqlite(.file("db.sqlite")), as: .sqlite)

    // Configure migrations
    app.migrations.add(CreateTodo())

    try routes(app)
}

最后是 routes.swift 文件。

func routes(_ app: Application) throws {
    app.get { req in
        return "It works!"
    }

    app.get("hello") { req in
        return "Hello, world!"
    }

    try app.register(collection: TodoController())
}

从中可以看出，Application 管理着各类基础组件（比如：Environment、Logger、Route 等等），并贯穿于程序的整个生命周期。