Get Attribute value using java reflection in two level.

I want to write global java method (using reflection) to convert object to CSV. when user gives map with field name as key and CSV header as value i want to create csv file using that data.

Suppose i have class User and User have address as attribute. Address is also object.

public class User {
    private String userName;
    private Address address;


    public String getUserName() {
        return userName;
    }

    public void setUserName(String userName) {
        this.userName = userName;
    }

    public Address getAddress() {
        return address;
    }

    public void setAddress(Address address) {
        this.address = address;
    }
}

public class Address {

    private String city;
    private String country;

    public String getCity() {
        return city;
    }

    public void setCity(String city) {
        this.city = city;
    }

    public String getCountry() {
        return country;
    }

    public void setCountry(String country) {
        this.country = country;
    }
}

I want to get user address city and country using reflection. suppose third party application pass address.city as key and i want to return city.

So what is the best way to find value using jave reflection.