1.目標：將http中的請求頭全部列印在Console中

2.基本語句

        //1.獲得指定的頭
        String header = response.getHeader("User-Agert");
        System.out.println(header);
        
        //2.獲得所有頭的名稱
        Enumeration<String> headerNames = request.getHeaderNames();
        while(headerNames.hasMoreElements()) {//
 
判斷是否還有下一個元素
            String nextElement = headerNames.nextElement();//獲取headerNames集合中的請求頭
            String header2 = request.getHeader(nextElement);//通過請求頭得到請求內容
            System.out.println(nextElement+":"+header2);

 3.執行結果

4.完整程式碼

package com.hdh.requesd;

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

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

public class requestHead extends HttpServlet {
    protected void doGet(HttpServletRequest request, HttpServletResponse response)
            
 
throws ServletException, IOException {
        // 1.獲得指定的頭
        String header = response.getHeader("User-Agert");
        System.out.println(header);

        // 2.獲得所有頭的名稱
        Enumeration<String> headerNames = request.getHeaderNames();
        while (headerNames.hasMoreElements()) {// 判斷是否還有下一個元素
            String nextElement = headerNames.nextElement();// 獲取headerNames集合中的請求頭
            String header2 = request.getHeader(nextElement);// 通過請求頭得到請求內容
            System.out.println(nextElement + ":" + header2);

        }

    }

    protected void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        doGet(request, response);
    }

}