java 文件的上传和下载

Posted 2020-10-10 TheStar

主要介绍使用 smartupload.jar 包中的方法对文件的上传和下载。上传时文件是存放在服务器中，我用的是tamcat。

首先建立一个servlet 类，对文件的操作

 1 package com.dkt.servlet;
 2 
 3 import java.io.File;
 4 import java.io.IOException;
 5 import java.sql.SQLException;
 6 import java.util.ArrayList;
 7 
 8 import javax.servlet.ServletException;
 9 import javax.servlet.http.HttpServlet;
10 import javax.servlet.http.HttpServletRequest;
11 import javax.servlet.http.HttpServletResponse;
12 
13 import org.lxh.smart.Files;
14 import org.lxh.smart.SmartUpload;
15 import org.lxh.smart.SmartUploadException;
16 
17 public class FileUpdownLoad extends HttpServlet {
18 
19     public void doGet(HttpServletRequest request, HttpServletResponse response)
20             throws ServletException, IOException {
21         doPost(request, response);
22     }
23 
24     public void doPost(HttpServletRequest request, HttpServletResponse response)
25             throws ServletException, IOException {
26 
27         response.setContentType("text/html");
28         request.setCharacterEncoding("GB2312");
29         response.setCharacterEncoding("GB2312");
30         SmartUpload su = new SmartUpload();
31         
32         String op = request.getParameter("op");
33         if (("upload").equals(op)) {
34             su.initialize(getServletConfig(), request, response);//初始化
35             su.setAllowedFilesList("txt,jpg,png,docx,xml,PNG,xlsx");//允许上传的文件类型，区分大小写
36             try {
37                 su.setDeniedFilesList("html,exe");//不允许上传的文件类型
38             } catch (SQLException e) {
39                 e.printStackTrace();
40             }
41             su.setMaxFileSize(5000000);//文件大小
42             
43             /*Files files = su.getFiles();
44             org.lxh.smart.File file2 = files.getFile(0);
45             System.out.println(file2.getFileName());
46             for(int i=0;i<files.getCount();i++){
47                 org.lxh.smart.File file = files.getFile(i);
48                 String fileName = file.getFileName();
49                 System.out.println("fileName---->"+fileName);
50                 fileName =  new String(fileName.getBytes("ISO-8859-1"),"GB2312");
51                 try {
52                     file.saveAs(fileName);
53                 } catch (SmartUploadException e) {
54                     e.printStackTrace();
55                 }
56             }*/
57             try {
58                 su.upload();//上传
59                 su.save("/smartUpdownload");//上传的路径，在tomcat下的文件夹中
60                 System.out.println("上传成功！！！");
61             } catch (SmartUploadException e) {
62                 e.printStackTrace();
63             }
64             request.getRequestDispatcher("fileUpDownload.jsp").forward(request, response);
65         }else if(("showFiles").equals(op)){
66             //得到上传到服务器的文件夹
67             String realPath = this.getServletContext().getRealPath("smartUpdownload");
68             //得到所有文件的文件名，并显示在页面上
69             File file = new File(realPath);
70             File[] listFiles = file.listFiles();
71             ArrayList<String> list = new ArrayList<String>();
72             for (File fi : listFiles) {
73                 list.add(fi.getName());//把所有的文件名存入集合
74             }
75             request.setAttribute("list", list);        
76             request.getRequestDispatcher("fileUpDownload.jsp").forward(request, response);
77         }else if(("download").equals(op)){
78             su.initialize(getServletConfig(), request, response);//初始化
79             su.setContentDisposition(null);
80             String filename1 = request.getParameter("filename");
81             String filename = new String(filename1.getBytes("ISO-8859-1"), "GB2312");
82             System.out.println(filename);
83             try {
84                 su.downloadFile("/smartUpdownload/"+filename);
85             } catch (SmartUploadException e) {
86                 e.printStackTrace();
87             }
88         }
89         
90         
91         
92         
93     }
94 
95 }

jsp 内容如下:

这里使用到了  c 标签，所以需要两个jar包  jstl.jar 和   standard-1.1.2.jar

并使用

<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c" %> 导入包

 1 <%@ page language="java" import="java.util.*" pageEncoding="gb2312"%>
 2 <%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c" %>
 3 <%@page import="org.lxh.smart.SmartUpload"%>
 4 <%@page import="org.lxh.smart.File"%>
 5 <%
 6 String path = request.getContextPath();
 7 String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
 8 %>
 9 
10 <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
11 <html>
12   <head>
13     <base href="<%=basePath%>">
14     
15     <title>My JSP \'fileUpDownload.jsp\' starting page</title>
16     
17     <meta http-equiv="pragma" content="no-cache">
18     <meta http-equiv="cache-control" content="no-cache">
19     <meta http-equiv="expires" content="0">    
20     <meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
21     <meta http-equiv="description" content="This is my page">
22     <!--
23     <link rel="stylesheet" type="text/css" href="styles.css">
24     -->
25 
26   </head>
27   
28   <body>
29     <form action="FileUpdownLoad?op=upload"  method="post" enctype="multipart/form-data" >
30             <input  type="file" name="file1" value="上传的文件">
31             <input type="submit" value="上传">
32     </form>
33     <hr/>
34     <a href = "FileUpdownLoad?op=showFiles">显示下载的文件目录</a><br/>
35     <c:forEach  items="${list}" var="filename">  
36         <a href="FileUpdownLoad?op=download&filename=${filename }">下载文件：${filename }</a><br/>
37     </c:forEach>
38     
39     <a href="ImageServlet">显示水印图片</a>
40   </body>
41 </html>