来自RFC 2616-sec 14
Host request-header字段指定所请求资源的Internet主机和端口号，从用户或引用资源提供的原始URI获得。

request.getHeader("Host");

字符串
将返回请求中的“Host”（在您的情况下为xxxxx.abcd.com）头的值。
你可以使用下面的程序来获取所有的头信息。

import java.io.IOException;
import java.io.PrintWriter;
import java.util.Enumeration;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
/**
 * Servlet implementation class RequestHeaderServlet
*/
@WebServlet("/RequestHeaderServlet")
public class RequestHeaderServlet extends HttpServlet {
private static final long serialVersionUID = 1L;
/**
 * @see HttpServlet#HttpServlet()
 */
public RequestHeaderServlet() {
    super();
    // TODO Auto-generated constructor stub
}
/**
 * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
 */
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    // TODO Auto-generated method stub
    response.setContentType("text/html");
    PrintWriter out = response.getWriter();
    Enumeration en = request.getHeaderNames();
    while(en.hasMoreElements()){
        //get header name Accept,Accept-Charset,Authorization,Connection,Host etc.   
        String headerName = (String) en.nextElement(); //nextElement() returns Object need type cast
        //get the value of the headerName 
        String headerValue = request.getHeader(headerName);
        //display on browser
        out.print("Header Name = "+ headerName + " " + " Header Value = "+ headerValue + "<br>");
    }
out.close();
}
/**
 * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
 */
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    // TODO Auto-generated method stub
 }
}

型

相关链接

• Servlet请求头
• tutorialspoint.com header example

它将返回请求中的“Host”头的值，该值必须是“从用户或引用资源给出的原始URI中获得的”。参见RFC 2616。