–典型的请求头信息 
–读取HTTP请求头 
–使用表格显示所有请求头信息 
–理解各种请求头的含义 
–区分不同的浏览器类型
##############Michael分割线###################
• 典型的请求头信息
image
• 读取HTTP请求头 
–使用HttpServletRequest中的方法 
• 一般方法 
 –getHeader (header名称不区分大小写) 
–getHeaders 
–getHeaderNames 
• 专门方法 
–getCookies 
–getAuthType 
–getRemoteUser 
–getContentLength 
–getContentType 
–getDateHeader 
–getIntHeader 
• 相关信息 
–getMethod 
–getRequestURI 
–getQueryString 
–getProtocol
• 使用表格显示有请求头信息
image
login.html
< !DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" >    
< html >    
     < head >    
         < title >login.html </title>    
         < meta  http-equiv ="keywords"  content ="keyword1,keyword2,keyword3" >    
         < meta  http-equiv ="description"  content ="this is my page" >    
         < meta  http-equiv ="content-type"  content ="text/html; charset=UTF-8" >    
         < ! --<link rel="stylesheet" type="text/css" href="./styles.css">-->    

     </head>    
     < body >    
         < form  name ="f1"  id ="f1"  action ="/Servlet_RequestHeader/servlet/RequestHeaderServlet"  method ="post" >    
             < table  border ="0" >    
                 < tr >    
                     < td >Login: </td>    
                     < td > < input  type ="text"  name ="login"  id ="login" > </td>    
                 </tr>    
                 < tr >    
                     < td >Password: </td>    
                     < td > < input  type ="password"  name ="password"  id ="password" > </td>    
                 </tr>    
                 < tr >    
                     < td  colspan ="2"  align ="center" > < input  type ="submit"  value ="login" > </td>    
                 </tr>    
             </table>    
         </form>    
     </body>    
</html> 
image
RequestHeaderServlet.java
package com.michael.servlet;    

import java.io.IOException;    
import java.io.PrintWriter;    
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 RequestHeaderServlet  extends HttpServlet {    

         /**    
         * Constructor of the object.    
         */    
         public RequestHeaderServlet() {    
                 super();    
        }    

         /**    
         * Destruction of the servlet. <br>    
         */    
         public  void destroy() {    
                 super.destroy();  // Just puts "destroy" string in log    
                 // Put your code here    
        }    

         /**    
         * The doGet method of the servlet. <br>    
         *    
         * This method is called when a form has its tag value method equals to get.    
         *    
         * @param request the request send by the client to the server    
         * @param response the response send by the server to the client    
         * @throws ServletException if an error occurred    
         * @throws IOException if an error occurred    
         */    
         public  void doGet(HttpServletRequest request, HttpServletResponse response)    
                         throws ServletException, IOException {    

                doPost(request,response);    
        }    

         /**    
         * The doPost method of the servlet. <br>    
         *    
         * This method is called when a form has its tag value method equals to post.    
         *    
         * @param request the request send by the client to the server    
         * @param response the response send by the server to the client    
         * @throws ServletException if an error occurred    
         * @throws IOException if an error occurred    
         */    
         public  void doPost(HttpServletRequest request, HttpServletResponse response)    
                         throws ServletException, IOException {    
                Enumeration names = request.getHeaderNames();                 

                response.setContentType( "text/html");    
                PrintWriter out = response.getWriter();    
                out    
                                .println( "<!DOCTYPE HTML PUBLIC \"-//W3C//DTD HTML 4.01 Transitional//EN\">");    
                out.println("<HTML>");    
                out.println("    <HEAD><TITLE>A Servlet</TITLE></HEAD>");    
                out.println("    <BODY>");    

                out.println("<table>");    
                out.println("<tr>");    
                out.println("<th>");    
                out.println("RequestHeader Name");    
                out.println("</th>");    
                out.println("<th>");    
                out.println("RequestHeader Value");    
                out.println("</th>");    
                out.println("</tr>");    
                while(names.hasMoreElements()){    
                        String name = (String) names.nextElement();    
                        String value = request.getHeader(name);    
                        out.println("<tr>");    
                        out.println("<td>");    
                        out.println(name);    
                        out.println("</td>");    
                        out.println("<td>");    
                        out.println(value);    
                        out.println("</td>");    
                        out.println("</tr>");    
                }    
                out.println("</table>");    
                out.println("    </BODY>");    
                out.println("</HTML>");    
                out.flush();    
                out.close();    
        }    

        /**    
         * Initialization of the servlet. <br>    
         *    
         * @throws ServletException if an error occure    
         */    
        public void init() throws ServletException {    
                // Put your code here    
        }    

} 
image
看下效果
image
image
• 理解各种请求头的含义 
– Accept 
• 标识浏览器能处理MIME类型 
• 能发送不同的内容到不同的客户端. 例如，PNG文件有好的压缩特性，但是在浏览器中支持的不是很广泛。 
• 一个Servlet可以检查是否支持PNG文件格式，如果支持 
– <IMG SRC=“picture.png” ...> 否则 
– <IMG SRC="picture.gif" ...> 
– Accept-Encoding 
• 标识浏览器能处理的编码类型 
– Authorization 
• 授权信息，通常出现在对服务器发送的WWW-Authenticate头的应答中 
– Connection 
• 表示是否需要持久连接。如果Servlet看到这里的值为“Keep-Alive”，或者看到请求使用的是HTTP 1.1（HTTP 1.1默认进行持久连接），它就可以利用持久连接的优点，当页面包含多个元素时（例如Applet，图片），显著地减少下载所需要的时间。要实现这一点，Servlet需要在应答中发送一个Content-Length头，最简单的实现方法是：先把内容写入ByteArrayOutputStream，然后在正式写出内容之前计算它的大小。 
– Cookie 
• 参考Java EE WEB工程师培训-JDBC+Servlet+JSP整合开发之16.Cookie
–Host 
• 包含一个URL，用户从该URL代表的页面出发访问当前请求的页面 
–If-Modified-Since 
• 只有当所请求的内容，在指定的日期之后，又经过修改才返回它，否则返回304“Not Modified”应答 
–Referer 
• 包含一个URL，用户从该URL代表的页面出发访问当前请求的页面。 
–User-Agent 
• 浏览器类型，如果Servlet返回的内容与浏览器类型有关则该值非常有用。
• 区分不同的浏览器类型 image
BrowserTypeServlet.java
package com.michael.servlet;    

import java.io.IOException;    
import java.io.PrintWriter;    

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

public  class BrowserTypeServlet  extends HttpServlet {    

         /**    
         * Constructor of the object.    
         */    
         public BrowserTypeServlet() {    
                 super();    
        }    

         /**    
         * Destruction of the servlet. <br>    
         */    
         public  void destroy() {    
                 super.destroy();  // Just puts "destroy" string in log    
                 // Put your code here    
        }    

         /**    
         * The doGet method of the servlet. <br>    
         *    
         * This method is called when a form has its tag value method equals to get.    
         *    
         * @param request the request send by the client to the server    
         * @param response the response send by the server to the client    
         * @throws ServletException if an error occurred    
         * @throws IOException if an error occurred    
         */    
         public  void doGet(HttpServletRequest request, HttpServletResponse response)    
                         throws ServletException, IOException {    

                doPost(request,response);    
        }    

         /**    
         * The doPost method of the servlet. <br>    
         *    
         * This method is called when a form has its tag value method equals to post.    
         *    
         * @param request the request send by the client to the server    
         * @param response the response send by the server to the client    
         * @throws ServletException if an error occurred    
         * @throws IOException if an error occurred    
         */    
         public  void doPost(HttpServletRequest request, HttpServletResponse response)    
                         throws ServletException, IOException {    
                String browserName = request.getHeader( "user-agent");    
                String result="";    
                 if(browserName.indexOf( "MSIE")!=-1){    
                        result =  "您当前使用的浏览器是IE!";    
                } else{    
                        result =  "您当前使用的浏览器是FireFox!";    
                }    

                response.setContentType( "text/html;charset=gbk");    
                PrintWriter out = response.getWriter();    
                out    
                                .println( "<!DOCTYPE HTML PUBLIC \"-//W3C//DTD HTML 4.01 Transitional//EN\">");    
                out.println("<HTML>");    
                out.println("    <HEAD><TITLE>A Servlet</TITLE></HEAD>");    
                out.println("    <BODY>");    
                out.println(result);    
                out.println("    </BODY>");    
                out.println("</HTML>");    
                out.flush();    
                out.close();    
        }    

        /**    
         * Initialization of the servlet. <br>    
         *    
         * @throws ServletException if an error occure    
         */    
        public void init() throws ServletException {    
                // Put your code here    
        }    

} 
image
测试
image
image
OK!
##############Michael分割线###################