Reactor, best practice to retrieve nested (multiple levels) objects?

Question

Suppose the following objects :

public class Employee {

    private Address address;

public class Address {

    private String street;
    private String country;

Which of the two following processes is the "best" (best practice and/or performance) ?

A :

return Mono.just(employee)
            .map(employee -> employee.getAddress().getCountry())

B :

return Mono.just(employee)
            .map(employee -> employee.getAddress())
            .map(address -> address.getCountry())

Answer 1

The second approach is more preferable:

return Mono.just(employee)
            .map(employee -> employee.getAddress())
            .map(address -> address.getCountry())

because you can make it simpler by adding a separete functions for each getter, or using method reference:

return Mono.just(employee).map(Emploee::getAddress).map(Address::getCountry)

It's obvious example, but in more complicated cases simplification of code by using method refecences could be significant. Moreover, method chaining employee.getAddress().getCountry() isn't a good practice. You can read more about method chaining discussion there.