HTTP Servlet Response完成文件下载、一次性验证码的实现

HTTP Servlet Response运行过程

通过Response设置响应行

package cn.aynortechnology.line;import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;public class StatusServlet extends HttpServlet {public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {//手动设置http响应行中的状态码response.setStatus(404);}public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {doGet(request, response);}
}

通过Response设置响应头

package cn.aynortechnology.header;import java.io.IOException;
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 Header extends HttpServlet {protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {Date date = new Date();//设置响应头//add在遇到同名的时候会加到后面response.addHeader("name", "aynor");response.addIntHeader("age", 21);response.addDateHeader("birthday", date.getTime());//setresponse.setHeader("name", "wangwang");response.setIntHeader("age", 23);}protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {doGet(request, response);}
}

重定向

重定向：
-状态码：302
-响应头：location代表重定向的地址
新建两个Servlet作为源和重定向测试一下
Servlet1

package cn.aynortechnology.header;import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;public class Servlet1 extends HttpServlet {public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {//没有响应资源 告知客户端去重定向到servlet2//1.设置状态码302response.setStatus(302);//2.设置响应头Locationresponse.setHeader("Location", "/WEB14/servlet2");}public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {doGet(request, response);}
}

Servlet2

package cn.aynortechnology.header;import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;public class Servlet2 extends HttpServlet {public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {response.getWriter().write("hello aynor");}public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {doGet(request, response);}
}

使用Servlet1直接跳转到Servlet2

一个封装好的方法

//封装成一个重定向的方法sendRedirect(url)
response.sendRedirect("/WEB14/servlet2");

定时刷新(跳转)

package cn.aynortechnology.header;import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;public class Refresh extends HttpServlet {public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {//设置定时刷新的头response.setHeader("refresh", "5;url=http://www.baidu.com");}public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {doGet(request, response);}
}

用js完成页面定时跳转

<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Insert title here</title>
<script type="text/javascript">window.onload = function(){var time = 5;var secondEle = document.getElementById("second");var timer = setInterval(function(){secondEle.innerHTML = time;time--;if(time==0){clearInterval(timer);location.href="http://www.baidu.com";}},1000);}
</script>
</head>
<body>恭喜您，注册成功，<span style="color:red" id="second">5</span>秒钟后跳转，如不跳转请点击<a href="http://www.baidu.com"'>这里</a>！
</body>
</html>

想要使用中文需要设置编码、解码方式

package cn.aynortechnology.content;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 TextServlet extends HttpServlet {public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {//writer.write("text");//设置response查询的码表//response.setCharacterEncoding("UTF-8"); PrintWriter writer = response.getWriter();//通过一个头Content-Type告知客户端使用何种码表进行解码//response.setHeader("Content-Type", "text/html;charset=UTF-8");response.setContentType("text/html;charset=UTF-8");writer.write("中国");}public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {doGet(request, response);}
}

用OutputStream输出字节流(此处以图片为例)

package cn.aynortechnology.content;import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;import javax.servlet.ServletException;
import javax.servlet.ServletOutputStream;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;public class ByteServlet extends HttpServlet {public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {//使用response获得一个字节输出流ServletOutputStream out = response.getOutputStream();//获得服务器上的图片String realPath = this.getServletContext().getRealPath("土味照片1.jpg");InputStream in = new FileInputStream(realPath);int len = 0;byte[] buffer = new byte[1024];while((len=in.read(buffer))>0) {out.write(buffer, 0, len);}in.close();out.close();}public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {doGet(request, response);}
}

前端代码

<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Insert title here</title>
</head>
<body><h1>使用a标签直接指向服务器上的资源</h1><a href="/WEB14/花纹库/龙角.jpg">龙角.jpg</a><br><a href="/WEB14/花纹库/图腾.jpg">图腾.jpg</a><br><h1>使用服务器端编码的方式实现文件下载</h1><a href="/WEB14/download?filename=龙角.jpg">龙角.jpg</a><br><a href="/WEB14/download?filename=图腾.jpg">图腾.jpg</a><br>
</body>
</html>

服务器端代码

package cn.aynortechnology.content;import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;import javax.servlet.ServletException;
import javax.servlet.ServletOutputStream;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;public class DownloadServlet extends HttpServlet {public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {//获得要下载的文件的名称String filename = request.getParameter("filename");//要下载的这个文件的类型---客户端通过文件的MIME类型取区分类型response.setContentType(this.getServletContext().getMimeType(filename));//告诉客户端该文件不是直接解析而是以附件形式打开(下载)response.setHeader("Content-Disposition", "attachment;filename="+filename);//获取文件的绝对路径String path = this.getServletContext().getRealPath("花纹库/"+filename);//获得该文件的输入流InputStream in = new FileInputStream(path);//获得输出流---通过response获得的输出流 用于向客户端写内容ServletOutputStream out = response.getOutputStream();//文件拷贝的模板代码int len = 0;byte[] buffer = new byte[1024];while((len=in.read(buffer))>0) {out.write(buffer, 0, len);}in.close();out.close();}public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {doGet(request, response);}
}

自适应浏览器下载中文文件名文件

package cn.aynortechnology.content;import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.net.URLEncoder;import javax.servlet.ServletException;
import javax.servlet.ServletOutputStream;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;import sun.misc.BASE64Encoder;public class DownloadServlet2 extends HttpServlet {public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {//*************文件名称是中文的下载**************////获得要下载的文件的名称String filename = request.getParameter("filename");//解决获得中文参数的乱码//filename = new String(filename.getBytes("ISO8859-1"),"UTF-8");filename = new String(filename.getBytes("ISO8859-1"),"UTF-8");//获得请求头中的User-AgentString agent = request.getHeader("User-Agent");//根据不同的客户端进行不同的编码if(agent.contains("MSIE")) {//IE浏览器filename = URLEncoder.encode(filename,"utf-8");filename = filename.replace("+", " ");}else if(agent.contains("Firefox")){//火狐浏览器BASE64Encoder base64Encoder = new BASE64Encoder();filename = "=?utf-8?B?"+base64Encoder.encode(filename.getBytes("utf-8"))+"?=";}else {//其他浏览器filename = URLEncoder.encode(filename, "utf-8");}//要下载的这个文件的类型---客户端通过文件的MIME类型取区分类型response.setContentType(this.getServletContext().getMimeType(filename));//告诉客户端该文件不是直接解析而是以附件形式打开(下载)response.setHeader("Content-Disposition", "attachment;filename="+filename);//获取文件的绝对路径String path = this.getServletContext().getRealPath("花纹库/"+filename);//获得该文件的输入流InputStream in = new FileInputStream(path);//获得输出流---通过response获得的输出流 用于向客户端写内容ServletOutputStream out = response.getOutputStream();//文件拷贝的模板代码int len = 0;byte[] buffer = new byte[1024];while((len=in.read(buffer))>0) {out.write(buffer, 0, len);}in.close();out.close();}public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {doGet(request, response);}
}

前端

<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Insert title here</title><script type="text/javascript">window.onload = function(){}function changeImg(obj){obj.src = "/WEB14/checkImg?time="+new Date().getTime();}
</script></head>
<body><form action="/WEB13/login" method="post">用户名：<input type="text" name="username"><br/>密码：<input type="password" name="password"><br/>验证码：<input type="text" name="username"><img onclick="changeImg(this)" src="/WEB14/checkImg"><br/><input type="submit" value="登录"><br/></form>
</body>
</html>

验证码代码

package cn.aynortechnology.checkimg;import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.image.BufferedImage;
import java.io.BufferedReader;
import java.io.FileReader;
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;
import java.util.Random;import javax.imageio.ImageIO;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;/*** 验证码生成程序* * * */
public class CheckImgServlet extends HttpServlet {// 集合中保存所有成语private List<String> words = new ArrayList<String>();@Overridepublic void init() throws ServletException {// 初始化阶段，读取new_words.txt// web工程中读取 文件，必须使用绝对磁盘路径String path = getServletContext().getRealPath("/WEB-INF/new_words.txt");try {BufferedReader reader = new BufferedReader(new FileReader(path));String line;while ((line = reader.readLine()) != null) {words.add(line);}reader.close();} catch (IOException e) {e.printStackTrace();}}public void doGet(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {// 禁止缓存// response.setHeader("Cache-Control", "no-cache");// response.setHeader("Pragma", "no-cache");// response.setDateHeader("Expires", -1);int width = 120;int height = 30;// 步骤一 绘制一张内存中图片BufferedImage bufferedImage = new BufferedImage(width, height,BufferedImage.TYPE_INT_RGB);// 步骤二 图片绘制背景颜色 ---通过绘图对象Graphics graphics = bufferedImage.getGraphics();// 得到画图对象 --- 画笔// 绘制任何图形之前 都必须指定一个颜色graphics.setColor(getRandColor(200, 250));graphics.fillRect(0, 0, width, height);// 步骤三 绘制边框graphics.setColor(Color.WHITE);graphics.drawRect(0, 0, width - 1, height - 1);// 步骤四 四个随机数字Graphics2D graphics2d = (Graphics2D) graphics;// 设置输出字体graphics2d.setFont(new Font("宋体", Font.BOLD, 18));Random random = new Random();// 生成随机数int index = random.nextInt(words.size());String word = words.get(index);// 获得成语// 定义x坐标int x = 10;for (int i = 0; i < word.length(); i++) {// 随机颜色graphics2d.setColor(new Color(20 + random.nextInt(110), 20 + random.nextInt(110), 20 + random.nextInt(110)));// 旋转 -30 --- 30度int jiaodu = random.nextInt(60) - 30;// 换算弧度double theta = jiaodu * Math.PI / 180;// 获得字母数字char c = word.charAt(i);// 将c 输出到图片graphics2d.rotate(theta, x, 20);graphics2d.drawString(String.valueOf(c), x, 20);graphics2d.rotate(-theta, x, 20);x += 30;}// 将验证码内容保存sessionrequest.getSession().setAttribute("checkcode_session", word);// 步骤五 绘制干扰线graphics.setColor(getRandColor(160, 200));int x1;int x2;int y1;int y2;for (int i = 0; i < 30; i++) {x1 = random.nextInt(width);x2 = random.nextInt(12);y1 = random.nextInt(height);y2 = random.nextInt(12);graphics.drawLine(x1, y1, x1 + x2, x2 + y2);}// 将上面图片输出到浏览器 ImageIOgraphics.dispose();// 释放资源ImageIO.write(bufferedImage, "jpg", response.getOutputStream());}public void doPost(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {doGet(request, response);}/*** 取其某一范围的color* * @param fc*            int 范围参数1* @param bc*            int 范围参数2* @return Color*/private Color getRandColor(int fc, int bc) {// 取其随机颜色Random random = new Random();if (fc > 255) {fc = 255;}if (bc > 255) {bc = 255;}int r = fc + random.nextInt(bc - fc);int g = fc + random.nextInt(bc - fc);int b = fc + random.nextInt(bc - fc);return new Color(r, g, b);}}

(页码SR1)HTTP Servlet Response设置响应头、重定向、定时刷新
(页码SR2)HTTP Servlet Response设置响应体、发送中文、图片
(页码SR3)HTTP Servlet Response文件下载基本代码
(页码SR4)HTTP Servlet Response一次性验证码的实现
整合：HTTP Servlet Response完成文件下载、一次性验证码的实现

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