Request.java

import java.net.MalformedURLException;
import java.net.URL;

import javax.servlet.http.HttpServletRequest;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Component;
import org.springframework.util.StringUtils;

@Component
public class Request {
    enum Header {
        HOST("Host"), REFERER("Referer");

        private String value;

        Header(String value) {
            this.value = value;
        }

        public String value() {
            return this.value;
        }

        @Override
        public String toString() {
            return value();
        }
    }

    @Autowired
    private HttpServletRequest request;

    public String getHeaderValue(String header) {
        return request.getHeader(header);
    }

    public String getHeaderValue(Header header) {
        return request.getHeader(header.value());
    }

    public String getHost() {
        // nao podemos usar o header Host pq o spring está o modificando
        String referer = getReferer();

        if (referer == null || StringUtils.isEmpty(referer)) {
            throw new RuntimeException("Referer can't be null!");
        }

        URL url;
        try {
            url = new URL(referer);
        }
        catch (MalformedURLException e) {
            throw new RuntimeException(String.format("Referer can't be invalid (%s)!", referer));
        }

        return extractRootUrl(url);
    }

    public String getReferer() {
        return getHeaderValue(Header.REFERER);
    }

    private String extractRootUrl(URL url) {
        StringBuilder sb = new StringBuilder();
        sb.append(url.getProtocol());
        sb.append("://");
        sb.append(url.getHost());

        if (hasPort(url)) {
            sb.append(":");
            sb.append(url.getPort());
        }

        return sb.toString();
    }

    private boolean hasPort(URL url) {
        return url.getPort() != -1;
    }
}