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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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