public interface PersonRepository {
 Mono<Person> getPerson(int id);
 Flux<Person> allPeople();
 Mono<Void> savePerson(Mono<Person> person);
}

RouterFunction<?> route = route(GET("/person/{id}"),
 request -> {
  Mono<Person> person = Mono.justOrEmpty(request.pathVariable("id"))
   .map(Integer::valueOf)
   .then(repository::getPerson);
  return Response.ok().body(fromPublisher(person, Person.class));
 })
 .and(route(GET("/person"),
  request -> {
   Flux<Person> people = repository.allPeople();
  return Response.ok().body(fromPublisher(people, Person.class));
 }))
 .and(route(POST("/person"),
 request -> {
  Mono<Person> person = request.body(toMono(Person.class));
 return Response.ok().build(repository.savePerson(person));
}));

HttpHandler httpHandler = RouterFunctions.toHttpHandler(route);
ReactorHttpHandlerAdapter adapter =
 new ReactorHttpHandlerAdapter(httpHandler);
HttpServer server = HttpServer.create("localhost", 8080);
server.startAndAwait(adapter);

$ curl 'http://localhost:8080/person/1'
{"name":"John Doe","age":42}

HandlerFunction<String> helloWorld =
 request -> Response.ok().body(fromObject("Hello World"));

RouterFunction<String> helloWorldRoute = 
 request -> {
  if (request.path().equals("/hello-world")) {
   return Optional.of(r -> Response.ok().body(fromObject("Hello World")));
  } else {
   return Optional.empty();
  }
 };

RouterFunction<String> helloWorldRoute =
 RouterFunctions.route(request -> request.path().equals("/hello-world"),
  request -> Response.ok().body(fromObject("Hello World")));

RouterFunction<String> helloWorldRoute =
 RouterFunctions.route(RequestPredicates.path("/hello-world"),
  request -> Response.ok().body(fromObject("Hello World")));
 

RouterFunction<?> route =
 route(path("/hello-world"),
  request -> Response.ok().body(fromObject("Hello World")))
 .and(route(path("/the-answer"),
  request -> Response.ok().body(fromObject("42"))));

RouterFunction<?> route =
 route(method(HttpMethod.GET).and(path("/hello-world")), 
  request -> Response.ok().body(fromObject("Hello World")))
 .and(route(method(HttpMethod.GET).and(path("/the-answer")), 
  request -> Response.ok().body(fromObject("42"))));

RouterFunction<?> route =
 route(GET("/hello-world"),
  request -> Response.ok().body(fromObject("Hello World")))
 .and(route(GET("/the-answer"),
  request -> Response.ok().body(fromObject(42))));

class DemoHandler {
 public Response<String> helloWorld(Request request) {
  return Response.ok().body(fromObject("Hello World"));
 }
 /* http://www.manongjc.com/article/1590.html */
 public Response<String> theAnswer(Request request) {
  return Response.ok().body(fromObject("42"));
 }
}

DemoHandler handler = new DemoHandler(); // or obtain via DI
RouterFunction<?> route =
 route(GET("/hello-world"), handler::helloWorld)
 .and(route(GET("/the-answer"), handler::theAnswer));
 

// http://www.manongjc.com
RouterFunction<?> route =
 route(GET("/hello-world"), handler::helloWorld)
 .and(route(GET("/the-answer"), handler::theAnswer))
 .filter((request, next) -> {
  System.out.println("Before handler invocation: " + request.path());
  Response<?> response = next.handle(request);
  Object body = response.body();
  System.out.println("After handler invocation: " + body);
 return response;
});

RouterFunction<String> route =
 route(GET("/hello-world"), handler::helloWorld)
 .andSame(route(GET("/the-answer"), handler::theAnswer))
 .filter((request, next) -> {
 Response<String> response = next.handle(request);
 String newBody = response.body().toUpperCase();
 return Response.from(response).body(fromObject(newBody));
 });

HttpHandler httpHandler = RouterFunctions.toHttpHandler(route);
HttpServlet servlet = new ServletHttpHandlerAdapter(httpHandler);
Tomcat server = new Tomcat();
Context rootContext = server.addContext("",
 System.getProperty("java.io.tmpdir"));
Tomcat.addServlet(rootContext, "servlet", servlet);
rootContext.addServletMapping("/", "servlet");
tomcatServer.start();