JavaWeb | 验证码、文件的“上传”与“下载”

验证码和文件的“上传”与“下载”

1.验证码

验证码：就是由服务器生成的一串随机数字或符号形成一幅图片，图片应该传给客户端，为了防止客户端用一些程序进行自动识别，在图片中通常需要添加一些干扰因素，由用户用肉眼来识别。
验证码在网络投票、交友论坛、网上商城等业务经常用来防止恶意客户侵入、恶意灌水、刷票。

1.1在JSP上开发验证码

loginForm.jsp

<%@ page language="java" pageEncoding="gb2312" %>
<html>
<head><title>第十三章 loginForm.jsp</title>
</head>
<body>
欢迎登录本系统<br>
<form action="/com/servlets/ValidateServlet" method="post">请输入你的账号: <input type="text" name="account"/><br>请输入你的密码: <input type="password" name="password"/><br>验证码: <input type="text" name="code" size="10"/><br><!-- 当验证码当做图片处理 --><img src="validate.jsp" border=0><input type="submit" value="登录">
</form>
</body>
</html>

web.xml

 <?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee"xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_4_0.xsd"version="4.0"><!--  访问到ValidateServlet.java类  -->
<servlet><servlet-name>validateServlet</servlet-name><servlet-class>com.servlets.ValidateServlet</servlet-class>
</servlet><servlet-mapping><servlet-name>validateServlet</servlet-name><url-pattern>/com/servlets/ValidateServlet</url-pattern>
</servlet-mapping>
</web-app>

ValidateServlet.class

/*
验证输入的验证码是否正确
*/
public class ValidateServlet extends HttpServlet { //用来验证表单登录的servletprotected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {//得到提交的验证码String code = request.getParameter("code");//获取session中的验证码HttpSession session = request.getSession();String randomStr = (String)session.getAttribute("randomStr"); //获取存储在session中的验证码response.setCharacterEncoding("gb2312");PrintWriter out = response.getWriter();//判断输入的验证码和生成的验证码是否相等if (!code.equals(randomStr)) {out.println("验证码错误！"); //在页面上显示} else {out.println("验证码正确！跳转到LoginServlet...");}}
}

validate.jsp

<%@ page import="java.awt.image.BufferedImage" %>
<%@ page import="java.awt.*" %>
<%@ page import="java.util.Random" %>
<%@ page import="javax.imageio.ImageIO" %>
<%@ page contentType="text/html;charset=gb2312" language="java" %>
<html>
<head><title>第十三章 validate.jsp</title>
</head>
<body>
<%response.setHeader("Cache-Control","no-cache");int width = 60;int height = 20;//1.实例化cBufferImage 对象BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);//2.从BufferImage中获取画笔Graphics类对象Graphics g = image.getGraphics();//设置画笔的属性g.setColor(new Color(200,200,200)); //设置颜色 / 设置背景颜色g.fillRect(0, 0, width, height); //设置生成的图片为长方形//3.生成随机数(4位数字)Random random = new Random();//这个随机数没有“种子”,用默认种子int randomNum  = random.nextInt(8999) +100; //左闭右开//转换为字符串String randomStr = String.valueOf(randomNum);//存入Session中session.setAttribute("randomStr",randomStr);//将验证码显示在图像中//用画笔画出干扰线和干扰电g.setColor(Color.black);g.setFont(new Font("", Font.PLAIN, 20));g.drawString(randomStr,10,17);//产生干扰点for (int i = 0; i < 100; i++) {int x = random.nextInt(width);int y = random.nextInt(height);g.drawOval(x,y,1,1);//干扰点为一个一个圆}//输出图像到页面response.setContentType("image/jpeg");ImageIO.write(image, "JPEG", response.getOutputStream());out.clear();out = pageContext.pushBody();
%>
</body>
</html>

loginForm_refresh.jsp

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head><title>第十三章: loginForm_refresh.jsp</title>
</head>
<body>
<%-- 具有刷新验证码功能的loginForm页面 --%>
<%-- 重新刷新验证码--%>
<script>function refresh() {//当点击验证码图片时就重新刷新img标签中的url//让url后面带一个随机数参数,来让每次访问的路径不一样，得到的验证码也不一样loginForm.imgValidate.src = "validate.jsp?id=" + Math.random() +";"}
</script>
欢迎登录本系统<br>
<%-- action中访问的为web.xml 中servlet标签中的 url --%>
<form name="loginForm" action="/com/servlets/ValidateServlet" method="post">请输入你的账号: <input type="text" name="account"/><br>请输入你的密码: <input type="password" name="password"/><br>验证码: <input type="text" name="code" size="10"/><br><!-- 当验证码当做图片处理 ,为该img标签添加"点击事件",让它被点击时,刷牙验证码--><img name = "imgValidate" src="validate.jsp"  οnclick="refresh()" border=0><input type="submit" value="登录">
</form>
</body>
</html>

2.“文件上传” 和 “文件下载”

2.1“文件上传 ”

在Java Web应用开发中，文件的上传是必不可少的，如上传简历、上传图片、上传资源代码等。
要实现文件上传，要导入 : jspsmart文件上传包。

fileTest.jsp ：

<%@ page  language="java" import="java.util.*" pageEncoding="gb2312" %>
<html>
<head><title>第十三章 文件上传: fileTest.jsp</title>
</head>
<body>
<form method="post" name="upload">
请你选择一个文件进行上传:<input type="file" name="myFile"><br><input type="submit" value="上传"><br>
</form>
</body>
</html>

web.xml

     <?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee"xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_4_0.xsd"version="4.0"><servlet><servlet-name>uploadServlet</servlet-name><servlet-class>com.servlets.UploadServlet</servlet-class>
</servlet><servlet-mapping><servlet-name>uploadServlet</servlet-name><url-pattern>/UploadServlet</url-pattern>
</servlet-mapping>
</web-app>

UploadServlet.java

public class UploadServlet extends HttpServlet { //关于文件上传的Servlet类@Overrideprotected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {//创建SmartUpload对象,其负责文件的上传SmartUpload smartUpload = new SmartUpload();//初始化SmartUpload对象//获得ServletConfig对象ServletConfig config = this.getServletConfig();smartUpload.initialize(config, request, response);try {//上传文件--调用.upload()方法上传文件smartUpload.upload();//获得上传的文件File file = smartUpload.getFiles().getFile(0);//保存文件file.saveAs("/S:/aaa/"+file.getFileName(),smartUpload.SAVE_PHYSICAL); //这个是存储在S盘中（物理路径存储）//file.saveAs("/img/"+file.getFileName(),smartUpload.SAVE_VIRTUAL);} catch (SmartUploadException e) {e.printStackTrace();}//上传成功了,保存成功上传的信息String msg = "Upload Success!";request.setAttribute("msg", msg);RequestDispatcher rd = request.getRequestDispatcher("/upload/第十三章/文件上传/uploadForm.jsp"); //上传完之后又回来点击内容进行上传的页面rd.forward(request, response);}
}

2.2“文件下载”

download2.jsp

<%@ page  language="java" pageEncoding="GB2312" import="java.util.*" %>
<html>
<head>
<title>第十三章 文件下载: download2.jsp</title>
</head>
<body>
文件下载
<hr>
<a href="/第十三章/文件下载/download.jsp?filename=java.jpg">下载</a>
</body>
</html>
download.jsp
<%@ page  language="java" pageEncoding="gb2312" import="java.util.*" %>
<html>
<head><title>文件下载: download.jsp</title>
</head>
<body>
<%String filename = request.getParameter("filename"); //获得url传参传递过来的参数//告诉客户端出现下载框,并指定下载框中的文件名response.setHeader("Content-Disposition","attachment;filename="+filename);//指定文件的类型response.setContentType("image/jpeg"); //jpeg//指定文件RequestDispatcher rd = request.getRequestDispatcher("/S:/aaa/"+filename);//rd.forward(request,response);
%>
</body>
</html>
此处给出常见文件对应的contentType类型，主要包括以下几种:
bmp : “application/x-bmp”;

doc: “application/msword”;

exe: “application/x-msdownload" ;

jpg: “image/jpeg" ;

mdb: “application/ msaccess”;

mp3: " audio/mp3”

pdf:”application/pdf";

ppt:”application/ vnd. ms-powerpoint";

rm:”application/vnd. rn- realmedia";

rmvb: “application/vnd. rn-realmedia-vbr”;

swf: “application/ x-shockwave-flash”;

xIs: “application/vnd. ms-excel”。