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Java Servlet文件上传

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平常项目中需要用到文件的上传,下面将详细介绍在Servlet中使用commons-fileupload-1.3.jar进行文件上传的经过。首先项目中要导入JAR包commons-fileupload-1.3.jar、commons-io-2.3.jar。但这也有缺点,不能上传大文件。

1、编写Servlet类

package com.fileupload;

import java.io.File;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.List;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.apache.commons.fileupload.FileItem;
import org.apache.commons.fileupload.disk.DiskFileItemFactory;
import org.apache.commons.fileupload.servlet.ServletFileUpload;

public class UpLoadServlet extends HttpServlet {
   public void doPost(HttpServletRequest request, HttpServletResponse response)
           throws ServletException, IOException {
       DiskFileItemFactory df = new DiskFileItemFactory();
       //设定阀值1M,如果超过这个值,则文件就直接写到临时文件,不会一直占用内存
       //利用这个特性可在上传大文件的时候不会占用大量内存,可以提高并发使用量。
       df.setSizeThreshold(1024 * 1024);
       
       try {
           File f = new File("E:\\preprocess_gd_package\\temp");
           if (!f.exists()) {
               f.mkdirs();
           }
           
           df.setRepository(f);
           ServletFileUpload sf = new ServletFileUpload(df);
           sf.setFileSizeMax(1024 * 1024 * 100);//上传文件最大为100M
           List list = sf.parseRequest(request);
           for (int i = 0; i < list.size(); i++) {
               FileItem fileItem = (FileItem) list.get(i);
               String filePath = fileItem.getName();  //获得文件路径+文件名
               if(filePath == null || "".equals(filePath.trim())){
                   continue;
               }
               int pos = filePath.lastIndexOf("\\");
               String fileName = filePath.substring(pos+1); //获取文件名
               
               File ff = new File("E:\\preprocess_gd_package\\files");
               if (!ff.exists()) {
                   ff.mkdirs();
               }
               
               File f2 = new File(ff, fileName);
               fileItem.write(f2);
           }
       } catch (Exception e) {
           e.printStackTrace();
       }

       response.setContentType("text/html");
       response.setCharacterEncoding("GBK");
       PrintWriter out = response.getWriter();
       out.println("<script>alert('文件上传成功!');</script>");
       out.flush();
       out.close();
   }

}

2、配置web.xml文件

<?xml version="1.0" encoding="UTF-8"?>
<web-app version="2.5" xmlns="http://java.sun.com/xml/ns/javaee"
   xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
   xsi:schemaLocation="http://java.sun.com/xml/ns/javaee
   http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd">
   <welcome-file-list>
       <welcome-file>index.jsp</welcome-file>
   </welcome-file-list>

   <servlet>
       <servlet-name>Upload</servlet-name>
       <servlet-class>com.fileupload.UpLoadServlet</servlet-class>
   </servlet>

   <servlet-mapping>
       <servlet-name>Upload</servlet-name>
       <url-pattern>/fileupload</url-pattern>
   </servlet-mapping>

</web-app>

3、编写index.jsp文件

<%@ page language="java" import="java.util.*" pageEncoding="GBK"%>
<%
   String path = request.getContextPath();
   String basePath = request.getScheme() + "://"
           + request.getServerName() + ":" + request.getServerPort()
           + path + "/";
%>

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
   <head>
       <base href="<%=basePath%>">
       <title>文件上传</title>
       <meta http-equiv="pragma" content="no-cache">
       <meta http-equiv="cache-control" content="no-cache">
       <meta http-equiv="expires" content="0">
       <meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
       <meta http-equiv="description" content="This is my page">
   </head>

   <body>
       <form action="fileupload" method="post" enctype="multipart/form-data" name="form1">
           <input type="file" name="file">
           <input type="submit" name="Submit" value="upload">
       </form>

   </body>
</html>

4、运行结果


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