servlet获取域名

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("/getDomain")
public class GetDomainServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        StringBuilder url = new StringBuilder();
        url.append(request.getScheme()).append("://").append(request.getServerName());
        if (request.getServerPort() != 80 && request.getServerPort() != 443) {
            url.append(":").append(request.getServerPort());
        }
        url.append(request.getRequestURI());

        response.setContentType("text/plain");
        response.getWriter().write("Full URL: " + url.toString());
    }
}