HttpServletResponse 学习

1： 利用Response向浏览器输出中文：

        private void test1(HttpServletResponse response) throws IOException {
		String data1 = "aaaa";
		String data2 = "中文";

		//向浏览器输出中文方法1： 利用 OutputStream 和 PrintWriter 输出
		//字节流可是输出任何东西， 注意response.getOutputStream(); 与  response.getWriter(); 不能同时存在
		/*
		  	OutputStream out = response.getOutputStream();
			out.write(data1.getBytes());
			out.write(data2.getBytes());
		*/
	    //字符流会出现中文乱码问题
		//解决方法
		response.setCharacterEncoding("UTF-8"); //设置response所查的码表
		PrintWriter pw = response.getWriter();

		pw.write(data1);
		pw.write(data2);
	}
        //向浏览器输出中文
	private void test2(HttpServletResponse response) throws IOException,
			UnsupportedEncodingException {
		String data = "中文";
		OutputStream out = response.getOutputStream();
		out.write("<meta http-equiv='content-type'  content='text/html; charset=UTF-8'>".getBytes()); //控制浏览器以什么码表解析
		out.write(data.getBytes("UTF-8"));  // 将数据以UTF-8码表所对应的编码发给浏览器
	}

　　

2： 实现web资源的下载：

//利用response实现文件下载
	private void teest3(HttpServletResponse response)
			throws UnsupportedEncodingException, FileNotFoundException,
			IOException {
		String path = this.getServletContext().getRealPath("/download/美女.jpg");
		String filename = path.substring(path.lastIndexOf("\\") + 1);
		System.out.println(path);
		System.out.println("filename = " + filename);

		//response.setHeader("content-disposition", "attachment; filename=" + filename);
		//中文的要进行URL编码
		response.setHeader("content-disposition", "attachment; filename=" + URLEncoder.encode(filename, "UTF-8"));
		InputStream in = new FileInputStream(path);
		OutputStream out = response.getOutputStream();
		int len = 0;
		byte[] buf = new byte[1024];
		while ((len = in.read(buf)) > 0) {
			out.write(buf, 0, len);
		}
	}

　　

3： 实现登陆注册时，验证码的生成与验证：

package cn.response.com;

import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.Random;

import javax.imageio.ImageIO;
import javax.jms.Session;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;

public class ResDemo2 extends HttpServlet {

	private int WIDTH = 120;
	private int HEIGHT = 25;
	public void doGet(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		BufferedImage bufimg = new BufferedImage(WIDTH, HEIGHT, BufferedImage.TYPE_INT_RGB);
		Graphics g = bufimg.getGraphics();

		HttpSession session = request.getSession();

		//1:设置背景色
		setBackGround(g);
		//2:设置边框
		setBorder(g);
		//3:画干扰线
		drawRandomLine(g);
		//4:写随机数
		drawRandomNum(session,(Graphics2D)g);
		//5图形写给浏览器

		 //设置浏览器不要缓存
		response.setHeader("expires", "-1");
		response.setHeader("Cache-Control", "no-cache");
		response.setHeader("Pragma", "no-cache");

		response.setContentType("image/jpeg");
		ImageIO.write(bufimg, "jpg", response.getOutputStream());
	}	

	private void setBackGround(Graphics g) {
		g.setColor(Color.WHITE);
		g.fillRect(0, 0, WIDTH, HEIGHT);
	}
	private void setBorder(Graphics g) {
		g.setColor(Color.BLUE);
		g.drawRect(1, 1, WIDTH - 2, HEIGHT - 2);
	}
	private void drawRandomLine(Graphics g) {
		g.setColor(Color.GREEN);

		for (int i = 0; i < 8; ++i) {
			int x1 = new Random().nextInt(WIDTH);
			int y1 = new Random().nextInt(HEIGHT);

			int x2 = new Random().nextInt(WIDTH);
			int y2 = new Random().nextInt(HEIGHT);
			g.drawLine(x1, y1, x2, y2);
		}
	}
	//常见中文的编码
	String base = "\u7684\u4e00\u4e86\u662f\u6211\u4e0d\u5728\u4eba\u4eec\u6709\u6765\u4ed6\u8fd9\u4e0a\u7740\u4e2a\u5730\u5230\u5927\u91cc\u8bf4\u5c31\u53bb\u5b50\u5f97\u4e5f\u548c\u90a3\u8981\u4e0b\u770b\u5929\u65f6\u8fc7\u51fa\u5c0f\u4e48\u8d77\u4f60\u90fd\u628a\u597d\u8fd8\u591a\u6ca1\u4e3a\u53c8\u53ef\u5bb6\u5b66\u53ea\u4ee5\u4e3b\u4f1a\u6837\u5e74\u60f3\u751f\u540c\u8001\u4e2d\u5341\u4ece\u81ea\u9762\u524d\u5934\u9053\u5b83\u540e\u7136\u8d70\u5f88\u50cf\u89c1\u4e24\u7528\u5979\u56fd\u52a8\u8fdb\u6210\u56de\u4ec0\u8fb9\u4f5c\u5bf9\u5f00\u800c\u5df1\u4e9b\u73b0\u5c71\u6c11\u5019\u7ecf\u53d1\u5de5\u5411\u4e8b\u547d\u7ed9\u957f\u6c34\u51e0\u4e49\u4e09\u58f0\u4e8e\u9ad8\u624b\u77e5\u7406\u773c\u5fd7\u70b9\u5fc3\u6218\u4e8c\u95ee\u4f46\u8eab\u65b9\u5b9e\u5403\u505a\u53eb\u5f53\u4f4f\u542c\u9769\u6253\u5462\u771f\u5168\u624d\u56db\u5df2\u6240\u654c\u4e4b\u6700\u5149\u4ea7\u60c5\u8def\u5206\u603b\u6761\u767d\u8bdd\u4e1c\u5e2d\u6b21\u4eb2\u5982\u88ab\u82b1\u53e3\u653e\u513f\u5e38\u6c14\u4e94\u7b2c\u4f7f\u5199\u519b\u5427\u6587\u8fd0\u518d\u679c\u600e\u5b9a\u8bb8\u5feb\u660e\u884c\u56e0\u522b\u98de\u5916\u6811\u7269\u6d3b\u90e8\u95e8\u65e0\u5f80\u8239\u671b\u65b0\u5e26\u961f\u5148\u529b\u5b8c\u5374\u7ad9\u4ee3\u5458\u673a\u66f4\u4e5d\u60a8\u6bcf\u98ce\u7ea7\u8ddf\u7b11\u554a\u5b69\u4e07\u5c11\u76f4\u610f\u591c\u6bd4\u9636\u8fde\u8f66\u91cd\u4fbf\u6597\u9a6c\u54ea\u5316\u592a\u6307\u53d8\u793e\u4f3c\u58eb\u8005\u5e72\u77f3\u6ee1\u65e5\u51b3\u767e\u539f\u62ff\u7fa4\u7a76\u5404\u516d\u672c\u601d\u89e3\u7acb\u6cb3\u6751\u516b\u96be\u65e9\u8bba\u5417\u6839\u5171\u8ba9\u76f8\u7814\u4eca\u5176\u4e66\u5750\u63a5\u5e94\u5173\u4fe1\u89c9\u6b65\u53cd\u5904\u8bb0\u5c06\u5343\u627e\u4e89\u9886\u6216\u5e08\u7ed3\u5757\u8dd1\u8c01\u8349\u8d8a\u5b57\u52a0\u811a\u7d27\u7231\u7b49\u4e60\u9635\u6015\u6708\u9752\u534a\u706b\u6cd5\u9898\u5efa\u8d76\u4f4d\u5531\u6d77\u4e03\u5973\u4efb\u4ef6\u611f\u51c6\u5f20\u56e2\u5c4b\u79bb\u8272\u8138\u7247\u79d1\u5012\u775b\u5229\u4e16\u521a\u4e14\u7531\u9001\u5207\u661f\u5bfc\u665a\u8868\u591f\u6574\u8ba4\u54cd\u96ea\u6d41\u672a\u573a\u8be5\u5e76\u5e95\u6df1\u523b\u5e73\u4f1f\u5fd9\u63d0\u786e\u8fd1\u4eae\u8f7b\u8bb2\u519c\u53e4\u9ed1\u544a\u754c\u62c9\u540d\u5440\u571f\u6e05\u9633\u7167\u529e\u53f2\u6539\u5386\u8f6c\u753b\u9020\u5634\u6b64\u6cbb\u5317\u5fc5\u670d\u96e8\u7a7f\u5185\u8bc6\u9a8c\u4f20\u4e1a\u83dc\u722c\u7761\u5174\u5f62\u91cf\u54b1\u89c2\u82e6\u4f53\u4f17\u901a\u51b2\u5408\u7834\u53cb\u5ea6\u672f\u996d\u516c\u65c1\u623f\u6781\u5357\u67aa\u8bfb\u6c99\u5c81\u7ebf\u91ce\u575a\u7a7a\u6536\u7b97\u81f3\u653f\u57ce\u52b3\u843d\u94b1\u7279\u56f4\u5f1f\u80dc\u6559\u70ed\u5c55\u5305\u6b4c\u7c7b\u6e10\u5f3a\u6570\u4e61\u547c\u6027\u97f3\u7b54\u54e5\u9645\u65e7\u795e\u5ea7\u7ae0\u5e2e\u5566\u53d7\u7cfb\u4ee4\u8df3\u975e\u4f55\u725b\u53d6\u5165\u5cb8\u6562\u6389\u5ffd\u79cd\u88c5\u9876\u6025\u6797\u505c\u606f\u53e5\u533a\u8863\u822c\u62a5\u53f6\u538b\u6162\u53d4\u80cc\u7ec6";
	private void drawRandomNum(HttpSession session, Graphics2D g) {
		g.setColor(Color.red);
		g.setFont(new Font("宋体",Font.BOLD, 20));
		int x = 5;
		String checkCode = "";
		for (int i = 0; i < 4; ++i) {
			String ch = base.charAt(new Random().nextInt(base.length())) + "";
			checkCode += ch;
			double degree = new Random().nextInt()%30;

			g.rotate(degree*Math.PI/180, x, 20);
			g.drawString(ch, x, 20);
			g.rotate(-degree*Math.PI/180, x, 20);
			x += 30;
		}
		session.setAttribute("checkCode", checkCode);
	}
	public void doPost(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		doGet(request, response);
	}

}

　　

登陆界面：

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
  <head>
    <base href="<%=basePath%>">

    <title>登陆</title>

	<meta http-equiv="pragma" content="no-cache">
	<meta http-equiv="cache-control" content="no-cache">
	<meta http-equiv="expires" content="0">
	<meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
	<meta http-equiv="description" content="This is my page">
	<!--
	<link rel="stylesheet" type="text/css" href="styles.css">
	-->
	<script type="text/javascript">

		function change(img) {

			img.src=img.src+"?"+new Date().getTime();
		}
	</script>
  </head>

  <body>
    <form action="/Test/ResDemo3">

    	用户名： <input type="text" name = "usrename"> <br/>
    	密码：  <input type="password" name = "password">  <br/>
    	验证码：<input type="text" name="checkCode" >
    	<img  src="/Test/ResDemo2" onclick="change(this)" alt="换一张" style="cursor: hand">  <br/>
    	<input type="submit" value="登陆">  <br/>
    </form>
  </body>
</html>

　　

验证：

package cn.response.com;

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;
import javax.servlet.http.HttpSession;

public class ResDemo3 extends HttpServlet {

	public void doGet(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		HttpSession session = request.getSession();
		System.out.println(session.getAttribute("checkCode"));
		String a = (String) session.getAttribute("checkCode");
		String b = (String) request.getParameter("checkCode");
		String tb = new String(b.getBytes("ISO-8859-1"), "UTF-8");
		if (a.equals(tb)) {
			response.sendRedirect("/Test/index.jsp");
		} else {
			System.out.println("error!");
		}
	}

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

}

　　

4：发送Http头，控制浏览器定时刷新

private void Test2(HttpServletResponse response) throws IOException {
		/*response.setHeader("refresh", "3;url='/Test/index.jsp'");
		//防止中文乱码， 设置编码
		response.setCharacterEncoding("UTF-8");
		response.setContentType("text/html; charset=UTF-8");

		response.getWriter().write("注册成功3秒后自动跳到主页");*/

		//利用<meta>标签来模拟响应头
		response.getWriter().write("<meta http-equiv='refresh'  content='3; url=/Test/index.jsp'>");
	}

	//refresh 实现每个3秒访问一次服务器，取回新数据， 可以用作OJ比赛排名时的Rank
	private void Test1(HttpServletResponse response) throws IOException {
		int data = new Random().nextInt();
		response.setHeader("refresh", "3");
		response.getWriter().write(data + "");
	}

　　

5： 禁止缓存，控制缓存

禁止缓存：

		 //设置浏览器不要缓存
		response.setHeader("expires", "-1");
		response.setHeader("Cache-Control", "no-cache");
		response.setHeader("Pragma", "no-cache");

　　

设置缓存：

	public void doGet(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		response.setDateHeader("expires", System.currentTimeMillis() + 1000*3600); // 设置缓存多久
		String data = "aaaa";
		response.getWriter().write(data);
	}

　　

6：请求重定向

	public void doGet(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		//重定向与转发
		/*
		 * 重定向，浏览器会向服务器发送两次请求， 生成2个request ，response
		 * 浏览器地址栏会发生变化
		 *
		 * 因为要向服务器发送两次请求， 所以重定向尽量不要用
		 *
		 * 主要用在： 登陆， 和购物车实现
		 */

		/*response.setStatus(302);
		response.setHeader("location", "/Test/index.jsp"); */
		//这一句等于上边两句话的执行
		response.sendRedirect("/Test/index.jsp");
	}