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 = "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";
	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");
	}