Spring-Webflux: Extracting Object from Mono without block()

I am new Spring Webflux. I am writing a simple api which call another api and returns response.
The problem I have is my api takes diffrent type of request than the external api.I have to convert the incoming request to send to external api.I am using Mono<T> to receive request for my api, but having trouble to convert to another object without block().

Input

Router

@Configuration
@EnableWebFlux
public class RouterConfig implements WebFluxConfigurer{
@Bean
public RouterFunction<ServerResponse> routes(UserHandler handler){
return RouterFunctions
.route(POST("/rest/create"),
handler::createUser);
}
} 

Handler

@Component
public class UserHandler {
private UserService service;
public UserHandler(UserService service) {
this.service = service;
}
public Mono<ServerResponse> saveUser(ServerRequest request) 
{
Mono<User> user = request.bodyToMono(User.class)
/* currently I am using block to get User object */
User user1 = user.block()
/* convert user to person */
Person p =getPersonFromUser(user);
}

Pojos

 class User
{
private String name;
private String id;
private String email;
private String phone;    
}
class Person
{
private String email;
/* Combination of id and name */
private String accountNumber;
private String phone;
}

Is there a way I can convert the Mono<User> to Person object without blocking?

If you're willing to have Person p processed in a Mono-Lambda, then you can try

public Mono<ServerResponse> saveUser(ServerRequest request) 
{
// Mono<User> user = request.bodyToMono(User.class)
request.bodyToMono(User.class)
// Convert a Mono<User> to a Mono<Person>    
.map((User user1) -> getPersonFromUser(user))
.map((Person p) -> {
// Code that either returns ServerResponse object or an intermediary object
})
// Additional code as needed

Because request.bodyToMono(User.class) returns a Mono of a User, you can call that Mono's map method. the map method takes in a lambda of type Function which takes in a parameter of one type and returns an object of a different type.

The first map call made:

.map((User user1) -> getPersonFromUser(user))

is given a Lambda that takes in a Function that converts a User to a Person, hence I jumped from having a "Mono for User" to a "Mono for Person".

I don't know if there is a way to get a ServerResponse directly from Person but in the second map call, you can write the function to return a ServerResponse (in which case you have a "Mono of a ServerResponse" and you're basically done) or return another intermediary object. If you do the latter, you'll likely need additional mapping calls.

Note: If within your Lambda, you get a Mono, you'll want to use the flatMap method, i.e. if getPersonFromUser(user) returns a Mono of a Person instead of a Person, then instead of

.map((User user1) -> getPersonFromUser(user))

you would use

.flatMap((User user1) -> getPersonFromUser(user))

You can checkout this StackOverFlow Question if you're interested in map vs flatmap