SpringBoot: how to obtain the user IP address?

ClientHostResolver.java

package br.com.zup.edu.nossocartao.propostas.shared.web;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Component;
import org.springframework.web.context.annotation.RequestScope;
import javax.servlet.http.HttpServletRequest;
import java.util.Objects;
import java.util.stream.Stream;

@Component
@RequestScope
public class ClientHostResolver {

    private final HttpServletRequest request;

    @Autowired
    public ClientHostResolver(HttpServletRequest request) {
        this.request = request;
    }

    /**
     * Resolves client IP address when application is behind a NGINX or other reverse proxy server
     */
    public String resolve() {

        String xRealIp = request.getHeader("X-Real-IP"); // used by Nginx
        String xForwardedFor = request.getHeader("X-Forwarded-For"); // used by the majority of load balancers
        String remoteAddr = request.getRemoteAddr(); // otherwise uses the remote IP address obtained by our Servlet container

        // returns the first non null
        return Stream.of(xRealIp, xForwardedFor, remoteAddr)
                     .filter(Objects::nonNull)
                     .findFirst().orElse(null);
    }

}

Important note: the X-Forwarded-For header may return a list of IP adresses, for example:

X-Forwarded-For: client, proxy1, proxy2

X-Forwarded-For: 203.0.113.195, 70.41.3.18, 150.172.238.178
X-Forwarded-For: 203.0.113.195
X-Forwarded-For: 2001:db8:85a3:8d3:1319:8a2e:370:7348