java文件上传Demo(必看篇)

时间：2021-05-19

说到文件上传我们要做到：

1.引入两个包：commons-fileupload-1.2.1.jar和commons-io-1.3.2.jar

2.将form改为上传文件模式：enctype="multipart/form-data"

3.开始编写相关代码

这里会用到几个关键的类：磁盘文件工厂DiskFileItemFactory ； 创建servlet文件上传类：ServletFileUpload

还有几个重要的方法：DiskFileItemFactory类用于将以临时文件形式保存在磁盘上的存放目录的方法setRepository；

ServletFileUpload类得到表单中所有的数据，得到form表单中所有的元素方法：parseRequest

下面看具体代码：

说明以这种方式上传文件是保存在服务器端的！

import java.io.File;import java.io.IOException;import java.io.PrintWriter;import java.util.ArrayList;import java.util.List;import java.util.UUID; 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.FileUploadException;import org.apache.commons.fileupload.disk.DiskFileItemFactory;import org.apache.commons.fileupload.servlet.ServletFileUpload;import org.apache.commons.io.FileUtils; public class UploadServlet extends HttpServlet { /** * Constructor of the object. */ public UploadServlet() { super(); } /** * Destruction of the servlet. <br> */ public void destroy() { super.destroy(); // Just puts "destroy" string in log // Put your code here } /** * The doGet method of the servlet. <br> * * This method is called when a form has its tag value method equals to get. * * @param request the request send by the client to the server * @param response the response send by the server to the client * @throws ServletException if an error occurred * @throws IOException if an error occurred */ public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { this.doPost(request, response); } /** * The doPost method of the servlet. <br> * * This method is called when a form has its tag value method equals to post. * * @param request the request send by the client to the server * @param response the response send by the server to the client * @throws ServletException if an error occurred * @throws IOException if an error occurred */ public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { response.setContentType("text/html"); PrintWriter out = response.getWriter(); DiskFileItemFactory sf= new DiskFileItemFactory();//实例化磁盘被文件列表工厂 String path = request.getRealPath("/upload");//得到上传文件的存放目录 sf.setRepository(new File(path));//设置文件存放目录 sf.setSizeThreshold(1024*1024);//设置文件上传小于1M放在内存中 String rename = "";//文件新生成的文件名 String fileName = "";//文件原名称 String name = "";//普通field字段 //从工厂得到servletupload文件上传类 ServletFileUpload sfu = new ServletFileUpload(sf); try { List<FileItem> lst = sfu.parseRequest(request);//得到request中所有的元素 for (FileItem fileItem : lst) { if(fileItem.isFormField()){ if("name".equals(fileItem.getFieldName())){ name = fileItem.getString("UTF-8"); } }else{ //获得文件名称 fileName = fileItem.getName(); fileName = fileName.substring(fileName.lastIndexOf("\\")+1); String houzhui = fileName.substring(fileName.lastIndexOf(".")); rename = UUID.randomUUID()+houzhui; fileItem.write(new File(path, rename)); } } } catch (Exception e) { // TODO Auto-generated catch block e.printStackTrace(); } System.out.println("普通字段"+name); System.out.println("文件名称"+fileName); System.out.println("修改后生成的文件名称"+rename); response.sendRedirect("ok.jsp"); out.flush(); out.close(); } /** * Initialization of the servlet. <br> * * @throws ServletException if an error occurs */ public void init() throws ServletException { // Put your code here } }

index.jsp页面：

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%><!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"><html> <head> <title>文件测试界面</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> <div align="center"> <form action="UploadServlet" enctype="multipart/form-data" method="post"> 名称：<input name="name" /> <br> 图片：<input name="img" type="file"/><br> <input type="submit" value="提交" /> <input type="reset" value="重置" /> </form> </div> </body></html>

ok.jsp页面：

<body> <h1 align="center">上传文件成功!</h1> </body>

实现效果就不截图了，有需要自己那过去用！

以上这篇java文件上传Demo(必看篇)就是小编分享给大家的全部内容了，希望能给大家一个参考，也希望大家多多支持。

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