Java EE WEB工程师培训-JDBC+Servlet+JSP整合开发之15.Servlet响应头信息-优快云博客

本文介绍了HTTP响应的基础知识，包括响应格式、报头设置等内容，并通过实例展示了如何利用Servlet构建Excel电子表格、动态生成JPEG图像及实现页面定时刷新。

–HTTP响应的格式
–设置响应报头
–常见MIME类型
–常见HTTP 1.1响应报头
–构建Excel电子表格
–动态生成JPEG图像
–定时刷新页面

###################Michael分割线#######################

• HTTP响应的格式

• 设置响应报头
– 设置任意响应头
• public void setHeader(String headerName, String headerValue)
– 设定任意的报头
• public void setDateHeader(String name,long millisecs)
– 将自1970年以来的毫秒数转换成GMT格式日期字符串
• public void setIntHeader(String name,int headerValue)
– 可以省去在调用setHeader之前将int转换成字符串的麻烦
• addHeader, addDateHeader, addIntHeader
– 增加新报头，而非替换已有的报头

– 普通响应报头的设置
• setContentType
– 设定Content-Type报头
– servlet几乎总会用到这个报头
– 参见常见MIME类型的表格
• setContentLength
– 设定Content-Length报头
– 用于持续性HTTP连接。
– 参见Connection请求报头
• addCookie
– 为Set-Cookie报头增加一个值
– 参见介绍cookie的部分
• sendRedirect
– 设定Location报头(以及改变状态代码)

• 常见MIME类型

• 常见HTTP 1.1响应报头
– Cache-Control (1.1) 和Pragma (1.0)
• no-cache值阻止浏览器缓存页面。
– Content-Disposition
• 通过这个报头，可以请求浏览器询问用户将响应存储到磁盘上给定名称的文件中
• Content-Disposition: attachment; filename=file-name
– Content-Encoding
• 文档的编码方式
– Content-Length
• 响应中的字节数
– Content-Type
• 返回文档时所采用的MIME类型。
• 使用setContentType设置这个报头。
– Expires
• 特定的一段时间，这段时间后应该将文档认作是过期，不应该再继续缓存
• 使用setDateHeader设置这个报头
– Last-Modified
• 文档最后被改动的时间
• 不要直接设置这个报头，而应该提供getLastModified方法
–Location
• 浏览器应该重新连接到的URL
• 不要直接设置这个报头，而要使用sendRedirect进行设定
–Refresh
• 多少秒后浏览器应该重新载入页面
–Set-Cookie
• 浏览器应该记下来的cookie。不要直接设置这个报头，而应该使用addCookie
–WWW-Authenticate
• 授权的类型和范围需要在Authorization报头中给出

• 构建Excel电子表格

Servlet_ResponseHeader

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 PrintExcelServlet extends HttpServlet {

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

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

 /**
 * The doGet method of the servlet. 
 *
 * 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. 
 *
 * 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 {

 response.setContentType( "application/vnd.ms-excel");
 PrintWriter out = response.getWriter();
 out.println( "\tQ1\tQ2\tQ3\tQ4\tTotal");
 out.println( "Apples\t78\t87\t92\t29\t=SUM(B2:E2)");
 out.println( "Oranges\t77\t86\t93\t30\t=SUM(B3:E3)");
 }

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

}

测试

• 动态生成JPEG图像

PrintPictureServlet.java

package com.michael.servlet;

import java.io.IOException;
import java.io.InputStream;
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 PrintPictureServlet extends HttpServlet {

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

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

 /**
 * The doGet method of the servlet. 
 *
 * 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. 
 *
 * 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 {

 response.setContentType( "image/jpeg");
 InputStream in = this.getClass().getClassLoader().getResourceAsStream( "Michael.JPG");
 int len = in.available();
 byte[] buffer = new byte[len];
 in.read(buffer);
 //输出流
 OutputStream out = response.getOutputStream();
 out.write(buffer);
 }

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

}

看下效果

• 定时刷新页面

TimeServlet.java

package com.michael.servlet;

import java.io.IOException;
import java.io.PrintWriter;
import java.util.Date;

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

public class TimeServlet extends HttpServlet {

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

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

 /**
 * The doGet method of the servlet. 
 *
 * 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. 
 *
 * 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 {
 response.setHeader( "refresh", "1");

 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.print(" 当前页面刷新时间为： ");
 out.print(new Date().toLocaleString());
 out.println(" </BODY>");
 out.println("</HTML>");
 out.flush();
 out.close();
 }

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

}