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：
