遍历HTTP请求所有头信息原理

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package cn.itcast.servlet.request;

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 RequestServlet2 extends HttpServlet {

    // 遍历HTTP请求中所有头信息
    public void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        // request.getHeaders 和 request.getHeaderNames
        // 获得所有头信息 key值集合
        Enumeration enumeration1 = request.getHeaderNames();
        while (enumeration1.hasMoreElements()) {
            String key = enumeration1.nextElement();
            System.out.println("头信息的key:" + key);
            Enumeration enumeration2 = request.getHeaders(key);
            while (enumeration2.hasMoreElements()) {
                String value = enumeration2.nextElement();
                System.out.println(key + ":" + value);
            }
        }
    }