Java如何获取servlet请求标头信息？

package org.nhooo.example.servlet;

import java.io.IOException;
import java.io.PrintWriter;
import java.util.Enumeration;

import javax.servlet.Servlet;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

 public class ServletRequestHeader extends HttpServlet implements Servlet {
    protected void doGet(HttpServletRequest request, 
            HttpServletResponse response) throws ServletException, IOException {
        response.setContentType("text/html");
        PrintWriter writer = response.getWriter(); 

        Enumeration enumeration = request.getHeaderNames();
        while (enumeration.hasMoreElements()) {
            // 获取请求标头名称
            String name = (String) enumeration.nextElement();

            // 获取请求标头值
            String value = request.getHeader(name);
            writer.println("Header [" + name + " = " + value + "<br/>");            

            // 读取请求值，以获取具有多个标题信息
            // 价值观。
            Enumeration values = request.getHeaders(name);
            while (values.hasMoreElements()) {
                value = (String) values.nextElement();
                writer.println("   Header [" + name + " = " + value + "<br/>");         
            }
        }
        writer.close();
    }   

    protected void doPost(HttpServletRequest request, 
            HttpServletResponse response) throws ServletException, IOException {
        // 没做什么！
    }               
}