An example of dynamic routing based on host

HostRoutingExample.java

package io.activej.launchers.http;

import io.activej.http.AsyncServlet;
import io.activej.http.HttpHeaders;
import io.activej.http.HttpResponse;
import io.activej.http.RoutingServlet;
import io.activej.inject.annotation.Named;
import io.activej.inject.annotation.Provides;

public final class HostRoutingExample extends HttpServerLauncher {
	private static final String TEST_HOST = "test.com";
	private static final String EXAMPLE_HOST = "example.com";

	@Provides
	AsyncServlet mainServlet(@Named("Test") AsyncServlet testServlet, @Named("Example") AsyncServlet exampleServlet) {
		return RoutingServlet.create()
				.map("/*", request -> {
					String hostHeader = request.getHeader(HttpHeaders.HOST);
					if (hostHeader == null) {
						return HttpResponse.ofCode(400).withPlainText("Host header is missing");
					}
					if (hostHeader.equals(TEST_HOST)) {
						return testServlet.serve(request);
					} else if (hostHeader.equals(EXAMPLE_HOST)) {
						return exampleServlet.serve(request);
					} else {
						return HttpResponse.ofCode(400).withPlainText("Unknown host");
					}
				});
	}

	@Provides
	@Named("Test")
	AsyncServlet testServlet() {
		return request -> HttpResponse.ok200().withHtml("<h1>This page is served on test.com</h1>");
	}

	@Provides
	@Named("Example")
	AsyncServlet exampleServlet() {
		return request -> HttpResponse.ok200().withHtml("<h1>This page is served on example.com</h1>");
	}

	public static void main(String[] args) throws Exception {
		new HostRoutingExample().launch(args);
	}
}