HTTP Servlet Response完成文件下载、一次性验证码的实现

约定不等于承诺〃 2023-07-07 12:41 8阅读 0赞

HTTP Servlet Response运行过程  
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**通过Response设置响应行**  
![在这里插入图片描述][20200222155516943.png]

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**  
![在这里插入图片描述][20200222155544835.png]

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());
    		//set
    		response.setHeader("name", "wangwang");
    		response.setIntHeader("age", 23);
    	}
    
    	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    		doGet(request, response);
    	}
    }

**重定向**  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQwOTIyODQ1_size_16_color_FFFFFF_t_70 2]  
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302
    		response.setStatus(302);
    		//2.设置响应头Location
    		response.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  
![在这里插入图片描述][20200222163218451.png]  
![在这里插入图片描述][20200222163242319.png]  
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>

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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);
    	}
    }

![在这里插入图片描述][20200222210757206.png]  
用OutputStream输出字节流(此处以图片为例)

![在这里插入图片描述][20200222212659138.png]  
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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);
    	}
    }

![在这里插入图片描述][20200223024128787.png]  
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![在这里插入图片描述][20200223034418167.png]  
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-Agent
    		String 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>();
     
    	@Override
    	public 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session
    		request.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 ImageIO
    		graphics.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][SR1_HTTP Servlet Response]  
[(页码SR2)HTTP Servlet Response设置响应体、发送中文、图片][SR2_HTTP Servlet Response]  
[(页码SR3)HTTP Servlet Response文件下载基本代码][SR3_HTTP Servlet Response]  
[(页码SR4)HTTP Servlet Response一次性验证码的实现][SR4_HTTP Servlet Response]  
整合：HTTP Servlet Response完成文件下载、一次性验证码的实现

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[20200222155516943.png]: https://img-blog.csdnimg.cn/20200222155516943.png
[20200222155544835.png]: https://img-blog.csdnimg.cn/20200222155544835.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQwOTIyODQ1_size_16_color_FFFFFF_t_70 2]: https://img-blog.csdnimg.cn/20200222162327178.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQwOTIyODQ1,size_16,color_FFFFFF,t_70
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[SR1_HTTP Servlet Response]: https://blog.csdn.net/qq_40922845/article/details/104444704
[SR2_HTTP Servlet Response]: https://blog.csdn.net/qq_40922845/article/details/104448580
[SR3_HTTP Servlet Response]: https://blog.csdn.net/qq_40922845/article/details/104452337
[SR4_HTTP Servlet Response]: https://blog.csdn.net/qq_40922845/article/details/104460218