JavaWeb | 验证码 、 文件的“上传”与“下载”

目录:

  • 验证码 和 文件的“上传”与“下载”
    • 1.验证码
      • 1.1在JSP上开发验证码
    • 2.“文件上传” 和 “文件下载”
      • 2.1“文件上传 ”
      • 2.2“文件下载”

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.jsptitle>
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>
 
 <img src="validate.jsp" border=0>
 <input type="submit" value="登录">
form>
body>
html>

web.xml

 
<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>validateServletservlet-name>
 <servlet-class>com.servlets.ValidateServletservlet-class>
servlet>

<servlet-mapping>
 <servlet-name>validateServletservlet-name>
 <url-pattern>/com/servlets/ValidateServleturl-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servlet

 protected 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" %>


 第十三章 validate.jsp


<%
 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();
%>


loginForm_refresh.jsp

<%@ page contentType="text/html;charset=UTF-8" language="java" %>


 第十三章: loginForm_refresh.jsp


<%-- 具有刷新验证码功能的loginForm页面 --%>
<%-- 重新刷新验证码--%>

欢迎登录本系统
<%-- action中访问的为web.xml 中servlet标签中的 url --%>
请输入你的账号:
请输入你的密码:
验证码:

2.“文件上传” 和 “文件下载”

2.1“文件上传 ”

  • Java Web应用开发中,文件的上传必不可少的,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" %>


 第十三章 文件上传: fileTest.jsp


请你选择一个文件进行上传:

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

 @Override
 protected 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.*" %>
    
    
    第十三章 文件下载: download2.jsp
    
    
    文件下载
    
    下载

    download.jsp

  • <%@ page  language="java" pageEncoding="gb2312" import="java.util.*" %>
    
    
        文件下载: download.jsp
    
    
    <%
        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);
    %>
    
    
    
  • 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”。

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