servlet获取二级域名

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;

@WebServlet("/getSubdomain")
public class SubdomainServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        String host = request.getHost();
        String[] parts = host.split("\\.");
        
        if (parts.length > 2) {
            String subdomain = parts[0];
            response.getWriter().println("二级域名: " + subdomain);
        } else {
            response.getWriter().println("无法获取二级域名");
        }
    }
}