I think it should be configured in the frontend like apache or proxy (nginx or other).

I would advise to redirect at your web server configuration, outside the Spring Boot aplication. But in case you want to redirect for some specific reason you could add Filter to your Spring Boot Configuration:

@Component
public class RedirectionFilter extends GenericFilterBean {

    @Override
    public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain)
            throws IOException, ServletException {

        final String host = request.getServerName();
    
        if (!org.apache.commons.lang.StringUtils.startsWithIgnoreCase(host, "www.")) {
            HttpServletRequest httpRequest = (HttpServletRequest) request;
            HttpServletResponse httpResponse = (HttpServletResponse) response;
            
            //obtain the full requested URL
            StringBuffer requestURL = httpRequest.getRequestURL();
            String queryString = httpRequest.getQueryString();
            if (queryString != null) {
                requestURL.append("?").append(queryString);
            }
            
            //set up redirect
            String redirectURL = requestURL.toString();
            redirectURL = redirectURL.replace(host, "www." + host);
            httpResponse.sendRedirect(redirectURL);
        }  else {
            chain.doFilter(request, response);
        }
    }
}