General information

Community

Quickstart

Add dependency

Maven

<dependency>    <groupId>io.javalin</groupId>    <artifactId>javalin</artifactId>    <version>6.7.0</version></dependency>

Gradle

implementation("io.javalin:javalin:6.7.0")

Start programming (Java)

importio.javalin.Javalin;publicclassHelloWorld {publicstaticvoidmain(String[]args) {varapp =Javalin.create(/*config*/)            .get("/",ctx ->ctx.result("Hello World"))            .start(7070);    }}

Start programming (Kotlin)

importio.javalin.Javalinfunmain() {val app=Javalin.create(/*config*/)        .get("/") { it.result("Hello World") }        .start(7070)}

Examples

Api structure and server config

importio.javalin.Javalinimportio.javalin.apibuilder.ApiBuilder.*funmain() {val app=Javalin.create { config->        config.useVirtualThreads=true        config.http.asyncTimeout=10_000L        config.staticFiles.add("/public")        config.staticFiles.enableWebjars()        config.router.apiBuilder {            path("/users") {                get(UserController::getAll)                post(UserController::create)                path("/{userId}") {                    get(UserController::getOne)                    patch(UserController::update)                    delete(UserController::delete)                }                ws("/events", userController::webSocketEvents)            }        }    }.start(7070)}

WebSockets

app.ws("/websocket/{path}") { ws->    ws.onConnect { ctx->println("Connected") }    ws.onMessage { ctx->val user= ctx.message<User>()// convert from json string to object        ctx.send(user)//  convert to json string and send back    }    ws.onClose { ctx->println("Closed") }    ws.onError { ctx->println("Errored") }}

Filters and Mappers

app.before("/some-path/*") { ctx->... }// runs before requests to /some-path/*app.before { ctx->... }// runs before all requestsapp.after { ctx->... }// runs after all requestsapp.exception(Exception.class) { e, ctx->... }// runs if uncaught Exceptionapp.error(404) { ctx->... }// runs if status is 404 (after all other handlers)app.wsBefore("/some-path/*") { ws->... }// runs before ws events on /some-path/*app.wsBefore { ws->... }// runs before all ws eventsapp.wsAfter { ws->... }// runs after all ws eventsapp.wsException(Exception.class) { e, ctx->... }// runs if uncaught Exception in ws handler

JSON-mapping

var todos= arrayOf(...)app.get("/todos") { ctx->// map array of Todos to json-string    ctx.json(todos)}app.put("/todos") { ctx->// map request-body (json) to array of Todos    todos= ctx.body<Array<Todo>>()    ctx.status(204)}

File uploads

app.post("/upload") { ctx->    ctx.uploadedFiles("files").forEach { uploadedFile->FileUtil.streamToFile(uploadedFile.content(),"upload/${uploadedFile.filename()}")    }}

Plugins

Javalin.create { config->    config.registerPlugin(MyPlugin())}

OpenAPI Plugin

@OpenApi(    summary="Get all users",    operationId="getAllUsers",    tags= ["User"],    responses= [OpenApiResponse("200", [OpenApiContent(Array<User>::class)])],    path="/users",    methods= [HttpMethod.GET])fungetAll(ctx:Context) {    ctx.json(UserService.getAll())}

SSL Plugin

val plugin=SSLPlugin { conf->    conf.pemFromPath("/path/to/cert.pem","/path/to/key.pem")}Javalin.create { javalinConfig->    javalinConfig.plugins.register(plugin)}.start()

Sponsors

Special thanks