java eclipse 文件上传和下载 java eclipse 中文件的上传和下载示例解析
java小斌 人气:0文件的上传与下载(一)
在实现文件上传和下载之前我们需要做一些准备工作,在Apache官网去下载文件上传下载的两个组件,下载链接这里给出:common-fileupload组件下载:http://commons.apache.org/proper/commons-fileupload/
common-io组件下载:http://commons.apache.org/proper/commons-io/
根据自己需求下载对应版本
一、创建工程
将所需要的两个开发包导入到工程项目中如图:
二、代码编写
1.前端页面代码
1). 在WebRoot目录下新建一个fileUpload.jsp页面,用来上传文件
<%@ page language="java" import="java.util.*" pageEncoding="GB18030"%> <% 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>My JSP 'fileUpload.jsp' starting page</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"> <!-- <link rel="stylesheet" type="text/css" href="styles.css"> --> </head> <body> <!-- 文件上传表单的提交方式必须是“post” 编码类型必须为:enctype="multipart/form-data" --> <form action="UploadServlet" method="post" enctype="multipart/form-data"> username: <input type="text" name="username" /><br> file: <input type="file" name="file"><br> file2: <input type="file" name="file2"><br> <input type="submit" value="上传文件"> </form> </body> </html>
2).新建一个fileUploadResult.jsp页面用来显示结果信息
<%@ page language="java" import="java.util.*,java.io.*" pageEncoding="GB18030"%> <% 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>My JSP 'fileUploadResult.jsp' starting page</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"> <!-- <link rel="stylesheet" type="text/css" href="styles.css"> --> </head> <body> <%-- <% //获取流对象 InputStream inputStream = request.getInputStream(); BufferedReader br = new BufferedReader(new InputStreamReader(inputStream)); String buffer = null; while((buffer = br.readLine()) != null){ out.print(buffer + "<br>"); } br.close(); inputStream.close(); %> --%> ${message}<br> EL-username : ${requestScope.username} <br> EL-file1 : ${requestScope.file }<br> EL-file2 : ${requestScope.file2}<br> </body> </html>
2. 编写上传文件处理的Servlet代码
1) UploadServlet.java代码如下:
package com.Servlet; import java.io.File; import java.io.FileOutputStream; import java.io.IOException; import java.io.InputStream; 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 { /** * 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 { //得到上传文件的保存目录,将上传的文件放在webRoot目录下(但是一般为了安全放在WEB-INF目录下,不允许外界直接访问,保证上传的安全) String path = this.getServletContext().getRealPath("/upload"); File file = new File(path); //判断上传文件的保存目录是否存在 if(!file.exists() && !file.isDirectory()){ System.out.println(path + "目录不存在,需要创建!"); //创建目录 file.mkdir(); } //消息提示 String message = ""; try{ //使用Apache文件上传组件处理文件上传步骤: //1.创建一个DiskFileItemFactory工厂 DiskFileItemFactory factory = new DiskFileItemFactory(); //2.创建一个文件上传解析器 ServletFileUpload upload = new ServletFileUpload(factory); //解决中文乱码 upload.setHeaderEncoding("UTF-8"); //3.判断提交的数据普通表单的数据还是带文件上传的表单 if(!upload.isMultipartContent(request)){ //如果是表单数据普通表单,则按照传统方式获取数据 return ; } //4.使用ServletFileUpload解析器解析上传数据,解析结果返回的是一个List<FileItem>集合,每一个FileItem对应一个Form表单的输入项 List<FileItem> list = upload.parseRequest(request); for(FileItem item : list){ //如果fileItem中封装的是普通输入项的数据 if(item.isFormField()){ //获取字段名字 String name = item.getFieldName(); //解决普通输入项中中文乱码问题 String value = item.getString("UTF-8");//value = new String(value.getBytes("iso8859-1"),"UTF-8"); System.out.println(name + " = " + value); }else{ //如果表单中提交的是上传文件 //获得上传的文件名称 String filename = item.getName(); System.out.println(filename); if(filename == null || filename.trim().equals(" ")){ continue; } //注意:不同的浏览器提交的文件名称是不一样的,有些浏览器提交的文件会带有路径,如“D:\\project\WebRoot\hello.jsp”,有一些是单纯的文件名:hello.jsp //去掉获取到文件名中的路径名,保留单纯的文件名 filename = filename.substring(filename.lastIndexOf("\\") + 1); //获取item中的上传文件的输入流 InputStream in = item.getInputStream(); //创建一个文件输入流 FileOutputStream out = new FileOutputStream(path + "\\" + filename); //创建一个缓冲区 byte buffer[] = new byte[1024]; //判断输入流中的数据是否已经读取完毕的标志位 int len = 0; //循环将输入流读入到缓冲区当中,(len = in.read(buffer)>0)就表示in里面还有数据存在 while((len = in.read(buffer)) > 0){ //使用FileOutputStream输出流将缓冲区的数据写入到指定的目录(path+"\\"+filename)当中 out.write(buffer, 0, len); } //关闭输入流 in.close(); //关闭输出流 out.close(); //删除处理文件上传生成的临时文件 item.delete(); message = "文件上传成功!"; } } }catch(Exception e){ message = "文件上传失败!"; e.printStackTrace(); } request.setAttribute(message, message); request.getRequestDispatcher("fileUploadResult.jsp").forward(request, response); } }
2)web.xml文件中的配置
<?xml version="1.0" encoding="UTF-8"?> <web-app version="3.0" 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_3_0.xsd"> <servlet> <servlet-name>UploadServlet</servlet-name> <servlet-class>com.Servlet.UploadServlet</servlet-class> </servlet> <servlet-mapping> <servlet-name>UploadServlet</servlet-name> <url-pattern>/UploadServlet</url-pattern> </servlet-mapping> </web-app>
结果:
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