request.getHeader("Host") 返回什么值

Question

我的申请链接是 https://xxxx.abcd.com

现在，当在浏览器中点击此 URL 时，如果我给出

，我会得到什么字符串中的值？

   String host=request.getHeader("Host");

Answer 1

来自 RFC 2616-sec14

主机请求标头字段指定所请求资源的互联网主机和端口号，从用户或引用资源给出的原始 URI 中获取。

request.getHeader("Host");

将返回请求中“Host”（在您的情况下为 xxxxx.abcd.com）标头的值。

您可以使用以下程序来获取所有标头信息。

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
 }
}

相关链接

• Servlet 教程请求标头
• tutorialspoint.com 标题示例

Answer 2

它将返回请求中“Host”标头的值，该值必须是“从用户或引用资源给出的原始 URI 获取的”。请参阅RFC 2616。

Answer 3

在您的情况下，您的字符串实际上得到 xxxxx.abcd.com