kotlin-ktor-patterns

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Ktor Server Patterns

Ktor 服务器模式

Comprehensive Ktor patterns for building robust, maintainable HTTP servers with Kotlin coroutines.

这是一套全面的Ktor模式，用于基于Kotlin协程构建健壮、可维护的HTTP服务器。

When to Activate

适用场景

Building Ktor HTTP servers
Configuring Ktor plugins (Auth, CORS, ContentNegotiation, StatusPages)
Implementing REST APIs with Ktor
Setting up dependency injection with Koin
Writing Ktor integration tests with testApplication
Working with WebSockets in Ktor

构建Ktor HTTP服务器
配置Ktor插件（认证、CORS、内容协商、状态页面）
使用Ktor实现REST API
通过Koin设置依赖注入
使用testApplication编写Ktor集成测试
在Ktor中使用WebSockets

Application Structure

应用结构

Standard Ktor Project Layout

标准Ktor项目结构

text

src/main/kotlin/
├── com/example/
│   ├── Application.kt           # Entry point, module configuration
│   ├── plugins/
│   │   ├── Routing.kt           # Route definitions
│   │   ├── Serialization.kt     # Content negotiation setup
│   │   ├── Authentication.kt    # Auth configuration
│   │   ├── StatusPages.kt       # Error handling
│   │   └── CORS.kt              # CORS configuration
│   ├── routes/
│   │   ├── UserRoutes.kt        # /users endpoints
│   │   ├── AuthRoutes.kt        # /auth endpoints
│   │   └── HealthRoutes.kt      # /health endpoints
│   ├── models/
│   │   ├── User.kt              # Domain models
│   │   └── ApiResponse.kt       # Response envelopes
│   ├── services/
│   │   ├── UserService.kt       # Business logic
│   │   └── AuthService.kt       # Auth logic
│   ├── repositories/
│   │   ├── UserRepository.kt    # Data access interface
│   │   └── ExposedUserRepository.kt
│   └── di/
│       └── AppModule.kt         # Koin modules
src/test/kotlin/
├── com/example/
│   ├── routes/
│   │   └── UserRoutesTest.kt
│   └── services/
│       └── UserServiceTest.kt

text

src/main/kotlin/
├── com/example/
│   ├── Application.kt           # 入口点，模块配置
│   ├── plugins/
│   │   ├── Routing.kt           # 路由定义
│   │   ├── Serialization.kt     # 内容协商设置
│   │   ├── Authentication.kt    # 认证配置
│   │   ├── StatusPages.kt       # 错误处理
│   │   └── CORS.kt              # CORS配置
│   ├── routes/
│   │   ├── UserRoutes.kt        # /users 端点
│   │   ├── AuthRoutes.kt        # /auth 端点
│   │   └── HealthRoutes.kt      # /health 端点
│   ├── models/
│   │   ├── User.kt              # 领域模型
│   │   └── ApiResponse.kt       # 响应封装
│   ├── services/
│   │   ├── UserService.kt       # 业务逻辑
│   │   └── AuthService.kt       # 认证逻辑
│   ├── repositories/
│   │   ├── UserRepository.kt    # 数据访问接口
│   │   └── ExposedUserRepository.kt
│   └── di/
│       └── AppModule.kt         # Koin模块
src/test/kotlin/
├── com/example/
│   ├── routes/
│   │   └── UserRoutesTest.kt
│   └── services/
│       └── UserServiceTest.kt

Application Entry Point

应用入口点

kotlin

// Application.kt
fun main() {
    embeddedServer(Netty, port = 8080, module = Application::module).start(wait = true)
}

fun Application.module() {
    configureSerialization()
    configureAuthentication()
    configureStatusPages()
    configureCORS()
    configureDI()
    configureRouting()
}

kotlin

// Application.kt
fun main() {
    embeddedServer(Netty, port = 8080, module = Application::module).start(wait = true)
}

fun Application.module() {
    configureSerialization()
    configureAuthentication()
    configureStatusPages()
    configureCORS()
    configureDI()
    configureRouting()
}

Routing DSL

路由DSL

Basic Routes

基础路由

kotlin

// plugins/Routing.kt
fun Application.configureRouting() {
    routing {
        userRoutes()
        authRoutes()
        healthRoutes()
    }
}

// routes/UserRoutes.kt
fun Route.userRoutes() {
    val userService by inject<UserService>()

    route("/users") {
        get {
            val users = userService.getAll()
            call.respond(users)
        }

        get("/{id}") {
            val id = call.parameters["id"]
                ?: return@get call.respond(HttpStatusCode.BadRequest, "Missing id")
            val user = userService.getById(id)
                ?: return@get call.respond(HttpStatusCode.NotFound)
            call.respond(user)
        }

        post {
            val request = call.receive<CreateUserRequest>()
            val user = userService.create(request)
            call.respond(HttpStatusCode.Created, user)
        }

        put("/{id}") {
            val id = call.parameters["id"]
                ?: return@put call.respond(HttpStatusCode.BadRequest, "Missing id")
            val request = call.receive<UpdateUserRequest>()
            val user = userService.update(id, request)
                ?: return@put call.respond(HttpStatusCode.NotFound)
            call.respond(user)
        }

        delete("/{id}") {
            val id = call.parameters["id"]
                ?: return@delete call.respond(HttpStatusCode.BadRequest, "Missing id")
            val deleted = userService.delete(id)
            if (deleted) call.respond(HttpStatusCode.NoContent)
            else call.respond(HttpStatusCode.NotFound)
        }
    }
}

kotlin

// plugins/Routing.kt
fun Application.configureRouting() {
    routing {
        userRoutes()
        authRoutes()
        healthRoutes()
    }
}

// routes/UserRoutes.kt
fun Route.userRoutes() {
    val userService by inject<UserService>()

    route("/users") {
        get {
            val users = userService.getAll()
            call.respond(users)
        }

        get("/{id}") {
            val id = call.parameters["id"]
                ?: return@get call.respond(HttpStatusCode.BadRequest, "Missing id")
            val user = userService.getById(id)
                ?: return@get call.respond(HttpStatusCode.NotFound)
            call.respond(user)
        }

        post {
            val request = call.receive<CreateUserRequest>()
            val user = userService.create(request)
            call.respond(HttpStatusCode.Created, user)
        }

        put("/{id}") {
            val id = call.parameters["id"]
                ?: return@put call.respond(HttpStatusCode.BadRequest, "Missing id")
            val request = call.receive<UpdateUserRequest>()
            val user = userService.update(id, request)
                ?: return@put call.respond(HttpStatusCode.NotFound)
            call.respond(user)
        }

        delete("/{id}") {
            val id = call.parameters["id"]
                ?: return@delete call.respond(HttpStatusCode.BadRequest, "Missing id")
            val deleted = userService.delete(id)
            if (deleted) call.respond(HttpStatusCode.NoContent)
            else call.respond(HttpStatusCode.NotFound)
        }
    }
}

Route Organization with Authenticated Routes

带认证的路由组织

kotlin

fun Route.userRoutes() {
    route("/users") {
        // Public routes
        get { /* list users */ }
        get("/{id}") { /* get user */ }

        // Protected routes
        authenticate("jwt") {
            post { /* create user - requires auth */ }
            put("/{id}") { /* update user - requires auth */ }
            delete("/{id}") { /* delete user - requires auth */ }
        }
    }
}

kotlin

fun Route.userRoutes() {
    route("/users") {
        // 公开路由
        get { /* 列出用户 */ }
        get("/{id}") { /* 获取用户 */ }

        // 受保护路由
        authenticate("jwt") {
            post { /* 创建用户 - 需要认证 */ }
            put("/{id}") { /* 更新用户 - 需要认证 */ }
            delete("/{id}") { /* 删除用户 - 需要认证 */ }
        }
    }
}

Content Negotiation & Serialization

内容协商与序列化

kotlinx.serialization Setup

kotlinx.serialization 配置

kotlin

// plugins/Serialization.kt
fun Application.configureSerialization() {
    install(ContentNegotiation) {
        json(Json {
            prettyPrint = true
            isLenient = false
            ignoreUnknownKeys = true
            encodeDefaults = true
            explicitNulls = false
        })
    }
}

kotlin

// plugins/Serialization.kt
fun Application.configureSerialization() {
    install(ContentNegotiation) {
        json(Json {
            prettyPrint = true
            isLenient = false
            ignoreUnknownKeys = true
            encodeDefaults = true
            explicitNulls = false
        })
    }
}

Serializable Models

可序列化模型

kotlin

@Serializable
data class UserResponse(
    val id: String,
    val name: String,
    val email: String,
    val role: Role,
    @Serializable(with = InstantSerializer::class)
    val createdAt: Instant,
)

@Serializable
data class CreateUserRequest(
    val name: String,
    val email: String,
    val role: Role = Role.USER,
)

@Serializable
data class ApiResponse<T>(
    val success: Boolean,
    val data: T? = null,
    val error: String? = null,
) {
    companion object {
        fun <T> ok(data: T): ApiResponse<T> = ApiResponse(success = true, data = data)
        fun <T> error(message: String): ApiResponse<T> = ApiResponse(success = false, error = message)
    }
}

@Serializable
data class PaginatedResponse<T>(
    val data: List<T>,
    val total: Long,
    val page: Int,
    val limit: Int,
)

kotlin

@Serializable
data class UserResponse(
    val id: String,
    val name: String,
    val email: String,
    val role: Role,
    @Serializable(with = InstantSerializer::class)
    val createdAt: Instant,
)

@Serializable
data class CreateUserRequest(
    val name: String,
    val email: String,
    val role: Role = Role.USER,
)

@Serializable
data class ApiResponse<T>(
    val success: Boolean,
    val data: T? = null,
    val error: String? = null,
) {
    companion object {
        fun <T> ok(data: T): ApiResponse<T> = ApiResponse(success = true, data = data)
        fun <T> error(message: String): ApiResponse<T> = ApiResponse(success = false, error = message)
    }
}

@Serializable
data class PaginatedResponse<T>(
    val data: List<T>,
    val total: Long,
    val page: Int,
    val limit: Int,
)

Custom Serializers

自定义序列化器

kotlin

object InstantSerializer : KSerializer<Instant> {
    override val descriptor = PrimitiveSerialDescriptor("Instant", PrimitiveKind.STRING)
    override fun serialize(encoder: Encoder, value: Instant) =
        encoder.encodeString(value.toString())
    override fun deserialize(decoder: Decoder): Instant =
        Instant.parse(decoder.decodeString())
}

kotlin

object InstantSerializer : KSerializer<Instant> {
    override val descriptor = PrimitiveSerialDescriptor("Instant", PrimitiveKind.STRING)
    override fun serialize(encoder: Encoder, value: Instant) =
        encoder.encodeString(value.toString())
    override fun deserialize(decoder: Decoder): Instant =
        Instant.parse(decoder.decodeString())
}

Authentication

认证

JWT Authentication

JWT 认证

kotlin

// plugins/Authentication.kt
fun Application.configureAuthentication() {
    val jwtSecret = environment.config.property("jwt.secret").getString()
    val jwtIssuer = environment.config.property("jwt.issuer").getString()
    val jwtAudience = environment.config.property("jwt.audience").getString()
    val jwtRealm = environment.config.property("jwt.realm").getString()

    install(Authentication) {
        jwt("jwt") {
            realm = jwtRealm
            verifier(
                JWT.require(Algorithm.HMAC256(jwtSecret))
                    .withAudience(jwtAudience)
                    .withIssuer(jwtIssuer)
                    .build()
            )
            validate { credential ->
                if (credential.payload.audience.contains(jwtAudience)) {
                    JWTPrincipal(credential.payload)
                } else {
                    null
                }
            }
            challenge { _, _ ->
                call.respond(HttpStatusCode.Unauthorized, ApiResponse.error<Unit>("Invalid or expired token"))
            }
        }
    }
}

// Extracting user from JWT
fun ApplicationCall.userId(): String =
    principal<JWTPrincipal>()
        ?.payload
        ?.getClaim("userId")
        ?.asString()
        ?: throw AuthenticationException("No userId in token")

kotlin

// plugins/Authentication.kt
fun Application.configureAuthentication() {
    val jwtSecret = environment.config.property("jwt.secret").getString()
    val jwtIssuer = environment.config.property("jwt.issuer").getString()
    val jwtAudience = environment.config.property("jwt.audience").getString()
    val jwtRealm = environment.config.property("jwt.realm").getString()

    install(Authentication) {
        jwt("jwt") {
            realm = jwtRealm
            verifier(
                JWT.require(Algorithm.HMAC256(jwtSecret))
                    .withAudience(jwtAudience)
                    .withIssuer(jwtIssuer)
                    .build()
            )
            validate { credential ->
                if (credential.payload.audience.contains(jwtAudience)) {
                    JWTPrincipal(credential.payload)
                } else {
                    null
                }
            }
            challenge { _, _ ->
                call.respond(HttpStatusCode.Unauthorized, ApiResponse.error<Unit>("Invalid or expired token"))
            }
        }
    }
}

// 从JWT中提取用户信息
fun ApplicationCall.userId(): String =
    principal<JWTPrincipal>()
        ?.payload
        ?.getClaim("userId")
        ?.asString()
        ?: throw AuthenticationException("No userId in token")

Auth Routes

认证路由

kotlin

fun Route.authRoutes() {
    val authService by inject<AuthService>()

    route("/auth") {
        post("/login") {
            val request = call.receive<LoginRequest>()
            val token = authService.login(request.email, request.password)
                ?: return@post call.respond(
                    HttpStatusCode.Unauthorized,
                    ApiResponse.error<Unit>("Invalid credentials"),
                )
            call.respond(ApiResponse.ok(TokenResponse(token)))
        }

        post("/register") {
            val request = call.receive<RegisterRequest>()
            val user = authService.register(request)
            call.respond(HttpStatusCode.Created, ApiResponse.ok(user))
        }

        authenticate("jwt") {
            get("/me") {
                val userId = call.userId()
                val user = authService.getProfile(userId)
                call.respond(ApiResponse.ok(user))
            }
        }
    }
}

kotlin

fun Route.authRoutes() {
    val authService by inject<AuthService>()

    route("/auth") {
        post("/login") {
            val request = call.receive<LoginRequest>()
            val token = authService.login(request.email, request.password)
                ?: return@post call.respond(
                    HttpStatusCode.Unauthorized,
                    ApiResponse.error<Unit>("Invalid credentials"),
                )
            call.respond(ApiResponse.ok(TokenResponse(token)))
        }

        post("/register") {
            val request = call.receive<RegisterRequest>()
            val user = authService.register(request)
            call.respond(HttpStatusCode.Created, ApiResponse.ok(user))
        }

        authenticate("jwt") {
            get("/me") {
                val userId = call.userId()
                val user = authService.getProfile(userId)
                call.respond(ApiResponse.ok(user))
            }
        }
    }
}

Status Pages (Error Handling)

状态页面（错误处理）

kotlin

// plugins/StatusPages.kt
fun Application.configureStatusPages() {
    install(StatusPages) {
        exception<ContentTransformationException> { call, cause ->
            call.respond(
                HttpStatusCode.BadRequest,
                ApiResponse.error<Unit>("Invalid request body: ${cause.message}"),
            )
        }

        exception<IllegalArgumentException> { call, cause ->
            call.respond(
                HttpStatusCode.BadRequest,
                ApiResponse.error<Unit>(cause.message ?: "Bad request"),
            )
        }

        exception<AuthenticationException> { call, _ ->
            call.respond(
                HttpStatusCode.Unauthorized,
                ApiResponse.error<Unit>("Authentication required"),
            )
        }

        exception<AuthorizationException> { call, _ ->
            call.respond(
                HttpStatusCode.Forbidden,
                ApiResponse.error<Unit>("Access denied"),
            )
        }

        exception<NotFoundException> { call, cause ->
            call.respond(
                HttpStatusCode.NotFound,
                ApiResponse.error<Unit>(cause.message ?: "Resource not found"),
            )
        }

        exception<Throwable> { call, cause ->
            call.application.log.error("Unhandled exception", cause)
            call.respond(
                HttpStatusCode.InternalServerError,
                ApiResponse.error<Unit>("Internal server error"),
            )
        }

        status(HttpStatusCode.NotFound) { call, status ->
            call.respond(status, ApiResponse.error<Unit>("Route not found"))
        }
    }
}

kotlin

// plugins/StatusPages.kt
fun Application.configureStatusPages() {
    install(StatusPages) {
        exception<ContentTransformationException> { call, cause ->
            call.respond(
                HttpStatusCode.BadRequest,
                ApiResponse.error<Unit>("Invalid request body: ${cause.message}"),
            )
        }

        exception<IllegalArgumentException> { call, cause ->
            call.respond(
                HttpStatusCode.BadRequest,
                ApiResponse.error<Unit>(cause.message ?: "Bad request"),
            )
        }

        exception<AuthenticationException> { call, _ ->
            call.respond(
                HttpStatusCode.Unauthorized,
                ApiResponse.error<Unit>("Authentication required"),
            )
        }

        exception<AuthorizationException> { call, _ ->
            call.respond(
                HttpStatusCode.Forbidden,
                ApiResponse.error<Unit>("Access denied"),
            )
        }

        exception<NotFoundException> { call, cause ->
            call.respond(
                HttpStatusCode.NotFound,
                ApiResponse.error<Unit>(cause.message ?: "Resource not found"),
            )
        }

        exception<Throwable> { call, cause ->
            call.application.log.error("Unhandled exception", cause)
            call.respond(
                HttpStatusCode.InternalServerError,
                ApiResponse.error<Unit>("Internal server error"),
            )
        }

        status(HttpStatusCode.NotFound) { call, status ->
            call.respond(status, ApiResponse.error<Unit>("Route not found"))
        }
    }
}

CORS Configuration

CORS配置

kotlin

// plugins/CORS.kt
fun Application.configureCORS() {
    install(CORS) {
        allowHost("localhost:3000")
        allowHost("example.com", schemes = listOf("https"))
        allowHeader(HttpHeaders.ContentType)
        allowHeader(HttpHeaders.Authorization)
        allowMethod(HttpMethod.Put)
        allowMethod(HttpMethod.Delete)
        allowMethod(HttpMethod.Patch)
        allowCredentials = true
        maxAgeInSeconds = 3600
    }
}

kotlin

// plugins/CORS.kt
fun Application.configureCORS() {
    install(CORS) {
        allowHost("localhost:3000")
        allowHost("example.com", schemes = listOf("https"))
        allowHeader(HttpHeaders.ContentType)
        allowHeader(HttpHeaders.Authorization)
        allowMethod(HttpMethod.Put)
        allowMethod(HttpMethod.Delete)
        allowMethod(HttpMethod.Patch)
        allowCredentials = true
        maxAgeInSeconds = 3600
    }
}

Koin Dependency Injection

Koin依赖注入

Module Definition

模块定义

kotlin

// di/AppModule.kt
val appModule = module {
    // Database
    single<Database> { DatabaseFactory.create(get()) }

    // Repositories
    single<UserRepository> { ExposedUserRepository(get()) }
    single<OrderRepository> { ExposedOrderRepository(get()) }

    // Services
    single { UserService(get()) }
    single { OrderService(get(), get()) }
    single { AuthService(get(), get()) }
}

// Application setup
fun Application.configureDI() {
    install(Koin) {
        modules(appModule)
    }
}

kotlin

// di/AppModule.kt
val appModule = module {
    // 数据库
    single<Database> { DatabaseFactory.create(get()) }

    // 仓库
    single<UserRepository> { ExposedUserRepository(get()) }
    single<OrderRepository> { ExposedOrderRepository(get()) }

    // 服务
    single { UserService(get()) }
    single { OrderService(get(), get()) }
    single { AuthService(get(), get()) }
}

// 应用配置
fun Application.configureDI() {
    install(Koin) {
        modules(appModule)
    }
}

Using Koin in Routes

在路由中使用Koin

kotlin

fun Route.userRoutes() {
    val userService by inject<UserService>()

    route("/users") {
        get {
            val users = userService.getAll()
            call.respond(ApiResponse.ok(users))
        }
    }
}

kotlin

fun Route.userRoutes() {
    val userService by inject<UserService>()

    route("/users") {
        get {
            val users = userService.getAll()
            call.respond(ApiResponse.ok(users))
        }
    }
}

Koin for Testing

测试中的Koin使用

kotlin

class UserServiceTest : FunSpec(), KoinTest {
    override fun extensions() = listOf(KoinExtension(testModule))

    private val testModule = module {
        single<UserRepository> { mockk() }
        single { UserService(get()) }
    }

    private val repository by inject<UserRepository>()
    private val service by inject<UserService>()

    init {
        test("getUser returns user") {
            coEvery { repository.findById("1") } returns testUser
            service.getById("1") shouldBe testUser
        }
    }
}

kotlin

class UserServiceTest : FunSpec(), KoinTest {
    override fun extensions() = listOf(KoinExtension(testModule))

    private val testModule = module {
        single<UserRepository> { mockk() }
        single { UserService(get()) }
    }

    private val repository by inject<UserRepository>()
    private val service by inject<UserService>()

    init {
        test("getUser returns user") {
            coEvery { repository.findById("1") } returns testUser
            service.getById("1") shouldBe testUser
        }
    }
}

Request Validation

请求验证

kotlin

// Validate request data in routes
fun Route.userRoutes() {
    val userService by inject<UserService>()

    post("/users") {
        val request = call.receive<CreateUserRequest>()

        // Validate
        require(request.name.isNotBlank()) { "Name is required" }
        require(request.name.length <= 100) { "Name must be 100 characters or less" }
        require(request.email.matches(Regex(".+@.+\\..+"))) { "Invalid email format" }

        val user = userService.create(request)
        call.respond(HttpStatusCode.Created, ApiResponse.ok(user))
    }
}

// Or use a validation extension
fun CreateUserRequest.validate() {
    require(name.isNotBlank()) { "Name is required" }
    require(name.length <= 100) { "Name must be 100 characters or less" }
    require(email.matches(Regex(".+@.+\\..+"))) { "Invalid email format" }
}

kotlin

// 在路由中验证请求数据
fun Route.userRoutes() {
    val userService by inject<UserService>()

    post("/users") {
        val request = call.receive<CreateUserRequest>()

        // 验证
        require(request.name.isNotBlank()) { "Name is required" }
        require(request.name.length <= 100) { "Name must be 100 characters or less" }
        require(request.email.matches(Regex(".+@.+\\..+"))) { "Invalid email format" }

        val user = userService.create(request)
        call.respond(HttpStatusCode.Created, ApiResponse.ok(user))
    }
}

// 或者使用验证扩展函数
fun CreateUserRequest.validate() {
    require(name.isNotBlank()) { "Name is required" }
    require(name.length <= 100) { "Name must be 100 characters or less" }
    require(email.matches(Regex(".+@.+\\..+"))) { "Invalid email format" }
}

WebSockets

kotlin

fun Application.configureWebSockets() {
    install(WebSockets) {
        pingPeriod = 15.seconds
        timeout = 15.seconds
        maxFrameSize = 64 * 1024 // 64 KiB — increase only if your protocol requires larger frames
        masking = false // Server-to-client frames are unmasked per RFC 6455; client-to-server are always masked by Ktor
    }
}

fun Route.chatRoutes() {
    val connections = Collections.synchronizedSet<Connection>(LinkedHashSet())

    webSocket("/chat") {
        val thisConnection = Connection(this)
        connections += thisConnection

        try {
            send("Connected! Users online: ${connections.size}")

            for (frame in incoming) {
                frame as? Frame.Text ?: continue
                val text = frame.readText()
                val message = ChatMessage(thisConnection.name, text)

                // Snapshot under lock to avoid ConcurrentModificationException
                val snapshot = synchronized(connections) { connections.toList() }
                snapshot.forEach { conn ->
                    conn.session.send(Json.encodeToString(message))
                }
            }
        } catch (e: Exception) {
            logger.error("WebSocket error", e)
        } finally {
            connections -= thisConnection
        }
    }
}

data class Connection(val session: DefaultWebSocketSession) {
    val name: String = "User-${counter.getAndIncrement()}"

    companion object {
        private val counter = AtomicInteger(0)
    }
}

kotlin

fun Application.configureWebSockets() {
    install(WebSockets) {
        pingPeriod = 15.seconds
        timeout = 15.seconds
        maxFrameSize = 64 * 1024 // 64 KiB — 仅当协议需要更大帧时再增加
        masking = false // 根据RFC 6455，服务器到客户端的帧无需掩码；Ktor会自动为客户端到服务器的帧添加掩码
    }
}

fun Route.chatRoutes() {
    val connections = Collections.synchronizedSet<Connection>(LinkedHashSet())

    webSocket("/chat") {
        val thisConnection = Connection(this)
        connections += thisConnection

        try {
            send("Connected! Users online: ${connections.size}")

            for (frame in incoming) {
                frame as? Frame.Text ?: continue
                val text = frame.readText()
                val message = ChatMessage(thisConnection.name, text)

                // 加锁创建快照以避免ConcurrentModificationException
                val snapshot = synchronized(connections) { connections.toList() }
                snapshot.forEach { conn ->
                    conn.session.send(Json.encodeToString(message))
                }
            }
        } catch (e: Exception) {
            logger.error("WebSocket error", e)
        } finally {
            connections -= thisConnection
        }
    }
}

data class Connection(val session: DefaultWebSocketSession) {
    val name: String = "User-${counter.getAndIncrement()}"

    companion object {
        private val counter = AtomicInteger(0)
    }
}

testApplication Testing

testApplication测试

Basic Route Testing

基础路由测试

kotlin

class UserRoutesTest : FunSpec({
    test("GET /users returns list of users") {
        testApplication {
            application {
                install(Koin) { modules(testModule) }
                configureSerialization()
                configureRouting()
            }

            val response = client.get("/users")

            response.status shouldBe HttpStatusCode.OK
            val body = response.body<ApiResponse<List<UserResponse>>>()
            body.success shouldBe true
            body.data.shouldNotBeNull().shouldNotBeEmpty()
        }
    }

    test("POST /users creates a user") {
        testApplication {
            application {
                install(Koin) { modules(testModule) }
                configureSerialization()
                configureStatusPages()
                configureRouting()
            }

            val client = createClient {
                install(io.ktor.client.plugins.contentnegotiation.ContentNegotiation) {
                    json()
                }
            }

            val response = client.post("/users") {
                contentType(ContentType.Application.Json)
                setBody(CreateUserRequest("Alice", "alice@example.com"))
            }

            response.status shouldBe HttpStatusCode.Created
        }
    }

    test("GET /users/{id} returns 404 for unknown id") {
        testApplication {
            application {
                install(Koin) { modules(testModule) }
                configureSerialization()
                configureStatusPages()
                configureRouting()
            }

            val response = client.get("/users/unknown-id")

            response.status shouldBe HttpStatusCode.NotFound
        }
    }
})

kotlin

class UserRoutesTest : FunSpec({
    test("GET /users returns list of users") {
        testApplication {
            application {
                install(Koin) { modules(testModule) }
                configureSerialization()
                configureRouting()
            }

            val response = client.get("/users")

            response.status shouldBe HttpStatusCode.OK
            val body = response.body<ApiResponse<List<UserResponse>>>()
            body.success shouldBe true
            body.data.shouldNotBeNull().shouldNotBeEmpty()
        }
    }

    test("POST /users creates a user") {
        testApplication {
            application {
                install(Koin) { modules(testModule) }
                configureSerialization()
                configureStatusPages()
                configureRouting()
            }

            val client = createClient {
                install(io.ktor.client.plugins.contentnegotiation.ContentNegotiation) {
                    json()
                }
            }

            val response = client.post("/users") {
                contentType(ContentType.Application.Json)
                setBody(CreateUserRequest("Alice", "alice@example.com"))
            }

            response.status shouldBe HttpStatusCode.Created
        }
    }

    test("GET /users/{id} returns 404 for unknown id") {
        testApplication {
            application {
                install(Koin) { modules(testModule) }
                configureSerialization()
                configureStatusPages()
                configureRouting()
            }

            val response = client.get("/users/unknown-id")

            response.status shouldBe HttpStatusCode.NotFound
        }
    }
})

Testing Authenticated Routes

认证路由测试

kotlin

class AuthenticatedRoutesTest : FunSpec({
    test("protected route requires JWT") {
        testApplication {
            application {
                install(Koin) { modules(testModule) }
                configureSerialization()
                configureAuthentication()
                configureRouting()
            }

            val response = client.post("/users") {
                contentType(ContentType.Application.Json)
                setBody(CreateUserRequest("Alice", "alice@example.com"))
            }

            response.status shouldBe HttpStatusCode.Unauthorized
        }
    }

    test("protected route succeeds with valid JWT") {
        testApplication {
            application {
                install(Koin) { modules(testModule) }
                configureSerialization()
                configureAuthentication()
                configureRouting()
            }

            val token = generateTestJWT(userId = "test-user")

            val client = createClient {
                install(io.ktor.client.plugins.contentnegotiation.ContentNegotiation) { json() }
            }

            val response = client.post("/users") {
                contentType(ContentType.Application.Json)
                bearerAuth(token)
                setBody(CreateUserRequest("Alice", "alice@example.com"))
            }

            response.status shouldBe HttpStatusCode.Created
        }
    }
})

kotlin

class AuthenticatedRoutesTest : FunSpec({
    test("protected route requires JWT") {
        testApplication {
            application {
                install(Koin) { modules(testModule) }
                configureSerialization()
                configureAuthentication()
                configureRouting()
            }

            val response = client.post("/users") {
                contentType(ContentType.Application.Json)
                setBody(CreateUserRequest("Alice", "alice@example.com"))
            }

            response.status shouldBe HttpStatusCode.Unauthorized
        }
    }

    test("protected route succeeds with valid JWT") {
        testApplication {
            application {
                install(Koin) { modules(testModule) }
                configureSerialization()
                configureAuthentication()
                configureRouting()
            }

            val token = generateTestJWT(userId = "test-user")

            val client = createClient {
                install(io.ktor.client.plugins.contentnegotiation.ContentNegotiation) { json() }
            }

            val response = client.post("/users") {
                contentType(ContentType.Application.Json)
                bearerAuth(token)
                setBody(CreateUserRequest("Alice", "alice@example.com"))
            }

            response.status shouldBe HttpStatusCode.Created
        }
    }
})

Configuration

配置

application.yaml

yaml

ktor:
  application:
    modules:
      - com.example.ApplicationKt.module
  deployment:
    port: 8080

jwt:
  secret: ${JWT_SECRET}
  issuer: "https://example.com"
  audience: "https://example.com/api"
  realm: "example"

database:
  url: ${DATABASE_URL}
  driver: "org.postgresql.Driver"
  maxPoolSize: 10

yaml

ktor:
  application:
    modules:
      - com.example.ApplicationKt.module
  deployment:
    port: 8080

jwt:
  secret: ${JWT_SECRET}
  issuer: "https://example.com"
  audience: "https://example.com/api"
  realm: "example"

database:
  url: ${DATABASE_URL}
  driver: "org.postgresql.Driver"
  maxPoolSize: 10

Reading Config

读取配置

kotlin

fun Application.configureDI() {
    val dbUrl = environment.config.property("database.url").getString()
    val dbDriver = environment.config.property("database.driver").getString()
    val maxPoolSize = environment.config.property("database.maxPoolSize").getString().toInt()

    install(Koin) {
        modules(module {
            single { DatabaseConfig(dbUrl, dbDriver, maxPoolSize) }
            single { DatabaseFactory.create(get()) }
        })
    }
}

kotlin

fun Application.configureDI() {
    val dbUrl = environment.config.property("database.url").getString()
    val dbDriver = environment.config.property("database.driver").getString()
    val maxPoolSize = environment.config.property("database.maxPoolSize").getString().toInt()

    install(Koin) {
        modules(module {
            single { DatabaseConfig(dbUrl, dbDriver, maxPoolSize) }
            single { DatabaseFactory.create(get()) }
        })
    }
}

Quick Reference: Ktor Patterns

快速参考：Ktor模式

Pattern	Description
`route("/path") { get { } }`	Route grouping with DSL
`call.receive<T>()`	Deserialize request body
`call.respond(status, body)`	Send response with status
`call.parameters["id"]`	Read path parameters
`call.request.queryParameters["q"]`	Read query parameters
`install(Plugin) { }`	Install and configure plugin
`authenticate("name") { }`	Protect routes with auth
`by inject<T>()`	Koin dependency injection
`testApplication { }`	Integration testing

Remember: Ktor is designed around Kotlin coroutines and DSLs. Keep routes thin, push logic to services, and use Koin for dependency injection. Test with

testApplication

for full integration coverage.

模式	说明
`route("/path") { get { } }`	使用DSL进行路由分组
`call.receive<T>()`	反序列化请求体
`call.respond(status, body)`	发送带状态码的响应
`call.parameters["id"]`	读取路径参数
`call.request.queryParameters["q"]`	读取查询参数
`install(Plugin) { }`	安装并配置插件
`authenticate("name") { }`	使用认证保护路由
`by inject<T>()`	Koin依赖注入
`testApplication { }`	集成测试

注意：Ktor基于Kotlin协程和DSL设计。保持路由简洁，将逻辑转移到服务层，并使用Koin进行依赖注入。使用

testApplication

实现完整的集成测试覆盖。