ResquestInfoServlet类通过访问HttpServletRequest对象的各种方法来读取HTTP请求中的特定信息，并且把它们写入到HTML中

ResquestInfoServlet.java

package com.demo.servlet;

import com.sun.xml.internal.ws.policy.privateutil.PolicyUtils;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.Enumeration;

/**
* Created by 谭雪娇 on 2017/4/5.
*/
public class RequestInfoServlet extends HttpServlet {
 /*响应客户请求*/
 public void doGet(HttpServletRequest request, HttpServletResponse response)throws IOException,ServletException {
 //设置HTTP响应的正文的类型
 response.setContentType("text/html;charset=GB2312");
 /*输出html文档*/
 PrintWriter out=response.getWriter();
 out.println("<html><head><title>RequestInfo</title></head>");
 out.println("<body>");
 out.println(" LocalAddr:"+request.getLocalAddr());
 out.println(" LocalName:"+request.getLocalName());
 out.println(" LocalPort:"+request.getLocalPort());
 out.println(" Protocol:"+request.getProtocol());
 out.println(" RemoteAddr:"+request.getRemoteAddr());
 out.println(" RemoteHost:"+request.getRemoteHost());
 out.println(" RemotePort:"+request.getRemotePort());
 out.println(" Method:"+request.getMethod());
 out.println(" URI:"+request.getRequestURI());
 out.println(" ContextPath:"+request.getContextPath());
 out.println(" QueryString:"+request.getQueryString());
 /*打印HTTP请求头*/
 out.println(" ***打印HTTP请求头***");
 Enumeration eu=request.getHeaderNames();
 while(eu.hasMoreElements()){
 String headerName=(String)eu.nextElement();
 out.println(" "+headerName+":"+request.getHeader(headerName));
 }
 out.println(" ***打印请求头结束*** ");
 out.println(" username :"+request.getParameter("username"));
 out.println("</body></html>");
 //关闭输入流
 out.close();

 }
}

web.xml

<servlet>
 <servlet-name>dispatcher</servlet-name>
 <servlet-class>com.demo.servlet.RequestInfoServlet</servlet-class>

</servlet>
<servlet-mapping>
 <servlet-name>dispatcher</servlet-name>
 <url-pattern>/info</url-pattern>
</servlet-mapping>

ResquestInfoServlet生成的HTML页面