package com.yyz.request;

 import java.io.IOException;
 import java.io.OutputStream;

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

 public class RequestDemo extends HttpServlet {

   public void doGet(HttpServletRequest request, HttpServletResponse response)
       throws ServletException, IOException {
     /**
     * URL是URI的子集。
     * URI用来标识一个资源。
     * URL用来标识互联网上的一个资源。
     */
     System.out.println(request.getRequestURL());//得到请求URL地址
     System.out.println(request.getRequestURI());//得到请求的资源
     System.out.println(request.getQueryString());
     System.out.println(request.getRemoteAddr());//得到来访者IP
     System.out.println(request.getRemoteHost());
     //由于没有在dns上注册所以打印结果还是127.0.0.1,如果是百度访问这个程序，则打印www.baidu.com
     System.out.println(request.getRemotePort());//得到请求的资源
     System.out.println(request.getMethod());//得到请求的资源
 }

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

 }

 package com.yyz.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;
 //获取请求头
 public class RequestDemo extends HttpServlet {

   public void doGet(HttpServletRequest request, HttpServletResponse response)
       throws ServletException, IOException {
     String head = request.getHeader("Accept-Encoding");
     //有些浏览器不支持压缩数据
     if(head.contains("gzip")){
       //输出压缩数据
     }else{
       //输出不压缩数据
     }
     //获取指定名称的头的所有值
     Enumeration e = request.getHeaders("Accept-Encoding");
     while(e.hasMoreElements()){
       String value = (String ) e.nextElement();
       System.out.println(value);
     }
     System.out.println("------------------------");
     //获取所有的头和值
     e = request.getHeaderNames();
     while(e.hasMoreElements()){
     String name = (String)e.nextElement();
     String   value = request.getHeader(name);
     System.out.println(name+"="+value);
     }
 }

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

 }

package com.yyz.request;
 import java.io.IOException;
 import java.util.Enumeration;
 import java.util.Map;
 import java.util.Map.Entry;
 import javax.servlet.ServletException;
 import javax.servlet.http.HttpServlet;
 import javax.servlet.http.HttpServletRequest;
 import javax.servlet.http.HttpServletResponse;
 //获取请求数据
 public class RequestDemo extends HttpServlet {
  public void doGet(HttpServletRequest request, HttpServletResponse response)
    throws ServletException, IOException {
   //http://localhost:8080/test/servlet/RequestDemo?name=yyz
   String value = request.getParameter("name");
   System.out .println(value);
   //http://localhost:8080/test/servlet/RequestDemo?like=sing&like=dance
   String likes[] = request.getParameterValues("like");
   if(likes!=null){
    for(String like : likes){
     System.out.println(like);
    }
   }
   //下面是这种遍历的专业写法,获取数组数据的方式（可避免空指针异常）
   for(int i=0;likes!=null&&i<likes.length;i++){
    System.out.println(likes[i]);
   }
   //获取所有名称，并根据名称获取值
   Enumeration e = request.getParameterNames();
   while(e.hasMoreElements()){
    String name = (String) e.nextElement();
    value = request.getParameter(name);
    System.out.println(name+"="+value);
   }
   System.out.println("----------------------");
   //得到request对象中用来封装数据的Map集合
   Map<String,String[]> map = request.getParameterMap();
   for(Entry<String, String[]> me : map.entrySet()){
    String name = me.getKey();
    String [] v = me.getValue();
    System.out.println(name+"="+v[0]);
   }
 } 
  public void doPost(HttpServletRequest request, HttpServletResponse response)
    throws ServletException, IOException {
   doGet(request,response);
 }
 }