Javalin 6 is finally here! (January 28th, 2024)

public static void main(String[] args) {
    var app = Javalin.create(/*config*/)
        .get("/", ctx -> ctx.result("Hello World"))
        .start(7070);
}

ctx.result(stringOrStream);           // writes string or input stream to client (`text/plain` by default)
ctx.json(myJson);                     // serializes object to JSON string and writes to client (as `application/json`)
ctx.jsonStream(myJson);               // serializes JSON directly to client (nothing buffered in memory)
ctx.writeSeekableStream(myMediaFile); // stream audio and video to client (supports seeking/skipping)
ctx.future(myFutureSupplier);         // instructs Javalin to handle request asynchronously
ctx.render("/file.ext", model);       // render template or markdown file (as `text/html`)

ctx.body();                     // get the request body as a string (caches the body)
ctx.formParam("name");          // get a form parameter
ctx.queryParam("name");         // get a query parameter
ctx.uploadedFile("name");       // get an uploaded file

// JSON methods
ctx.bodyAsClass(Clazz);         // deserialize ctx.body() to class
ctx.bodyStreamAsClass(Clazz);   // consume input stream from request body and deserialize to class

// validation
var age = ctx.queryParamAsClass("age", Integer.class)  // wraps parameter in Validator
    .check(age -> age > 18, "NOT_OLD_ENOUGH") // adds check with error message
    .get(); // gets the validated value, or throws ValidationException
var bananaBox = ctx.bodyValidator(BananaBox.class)
    .check(box -> box.weight < 5, ValidationError("WEIGHT_TOO_HIGH", Map.of("MAX_WEIGHT", 5)))
    .check(box -> box.bananas.length > 20, ValidationError("NOT_ENOUGH_BANANAS", Map.of("MIN_BANANAS", 20)))
    .getOrDefault(defaultBananaBox) // uses default if body is null, runs validation rules otherwise

app.ws("/websocket/{path}", ws -> {
    ws.onConnect(ctx -> System.out.println("Connected"));
    ws.onMessage(ctx -> {
        var user = ctx.messageAsClass(User.class); // convert from json
        ctx.send(user); // convert to json and send back
    });
    ws.onBinaryMessage(ctx -> System.out.println("Message"))
    ws.onClose(ctx -> System.out.println("Closed"));
    ws.onError(ctx -> System.out.println("Errored"));
});

app.sse("/sse", client -> {
    client.sendEvent("connected", "Hello, SSE");  // can also send an object, which will be serialized
    client.onClose(() -> System.out.println("Client disconnected"));
});

// app object
var app = Javalin.create(/*config*/)
    .get("/", ctx -> ctx.result("Hello World"))
    .start(7070);

// config.router object
var app = Javalin.create(config -> {
    config.router.mount(router -> { // access to router instance
        router.get("/", ctx -> ctx.result("Hello World"));
    });
    config.router.apiBuilder(() -> { // sets a static variable scoped to the lambda
        path("users", () -> { // statically imported to improve readability
            get(UserController::getAll);
            post(UserController::create);
            path(":user-id", () -> {
                get(UserController::getOne);
                patch(UserController::update);
                delete(UserController::delete);
            });
        });
    });
}).start(7070);

var app = Javalin.create(config -> {
    config.http.asyncTimeout = 10_000L;
    config.router.ignoreTrailingSlashes = true;
    config.staticFiles.add("/public", Location.CLASSPATH);
});

var app = Javalin.create(config -> {
    config.jetty.threadPool = new QueuedThreadPool();
    config.jetty.modifyWebSocketServletFactory(factory -> {});
    config.jetty.modifyServer(server -> {});
    config.jetty.modifyServletContextHandler(handler -> {});
    config.jetty.addConnector((server, httpConfig) -> new ServerConnector(server));
});

Javalin.create(config -> {
    config.registerPlugin(new ExamplePlugin(exampleConfig -> {
        exampleConfig.exampleSetting = "example";
    }));
});