在JSP页面实现文件的上传与下载

准备工作,引入jar包:

commons-fileupload-1.2.1.jar

commons-io-1.4

java页:

package com.baidu.com;

import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
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.FileUploadException;
import org.apache.commons.fileupload.disk.DiskFileItemFactory;
import org.apache.commons.fileupload.servlet.ServletFileUpload;

import com.sun.xml.internal.bind.v2.runtime.Name;
public class Test4 extends HttpServlet {
	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		try {
		//先建立磁盘文件项工厂
		DiskFileItemFactory diskFileItemFactory =new DiskFileItemFactory();
		//创建一个核心解析类
		ServletFileUpload fileupload = new ServletFileUpload(diskFileItemFactory);
		//利用核心解析类解析Request
		
			List<FileItem> list = fileupload.parseRequest(request);
			//遍历这个List集合,得到代表每个部分的文件项对象,根据判断是否是文件
			for (FileItem fileItem : list) {
				//判断这个问津是普通箱还是文件上传项
				if (fileItem.isFormField()) {
					//普通箱
					//接受普通项目的值
					//如果是普通箱那就取普通项的名称和值(接受值不能再使用request.getparameter())
					String name = fileItem.getFieldName();
					//拿普通类型的值
					String value = fileItem.getString("UTF-8");
					System.out.println("输出打印 :"+ name +"       "+value);
					//
				}else {
					//文件上传项
					//获得文件上传的文件名称
					String filename = fileItem.getName();
					//获得文件上传的文件数据
					InputStream is = fileItem.getInputStream();
					//获得文件上传的文件的路径 ,池畔的绝对路径
					String realpath = getServletContext().getRealPath("./a");
					//创建一个输出流写入到刚才(上面)的设置的路径中
					OutputStream os = new FileOutputStream(realpath+"/"+filename);
					//以下两个输出流,利用之前所学的数组传输字节流对象
					//定义一个int类型的变量
					int len = 0;
					//定义一个byte类型的数组
					byte[] b = new byte[1024];
					while ((len = is.read(b))!= -1) {
						os.write(b, 0, len);
						
					}
					os.close();
					is.close();
					
					
					
					
				}
			}
			
			
			
		} catch (FileUploadException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
		
	}
	

	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		doGet(request, response);
	}

}

.jsp页:

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTf-8">
<title>Insert title here</title>
</head>
<body>
<h1>文件上传</h1>
<form action="/shangchuanxiazai/Test1" method="post" enctype="multipart/form-data">
文件描述:<input type ="text" name="info"><br>
文件上传:<input type="file" name = "up"><br>
<input type = "submit" value="上传"> 


</form>
</body>
</html>