文件上传下载-白红宇

文件上传下载

阅读量：4102 次

发布时间：2019-05-25

本文共 5317 字，大约阅读时间需要 17 分钟。

文件上传原理

表单method属性应该设置为POST方法，不能使用GET方法。

表单enctype属性应该设置为multipart/form-data.

表单action属性应该设置为在后端服务器上处理文件上传的Servlet文件。下面的实例使用了UploadServletServlet来上传文件。

上传单个文件，您应该使用单个带有属性type="file"的<input.../>标签。为了允许多个文件上传，请包含多个name属性值不同的input标签。输入标签具有不同的名称属性的值。浏览器会为每个input标签关联一个浏览按钮

需要jar包

定义form

<%@ page language="java" contentType="text/html; charset=UTF-8"    pageEncoding="UTF-8"%><%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c" %>   
    Insert title here	
    	
    		
     		
     	
    
	
    
              	
    
    
		 	
		           			       文件名 			       下载 		      
		      			       ${item.name} 			       下载

文件名	下载
${item.name}	下载

文件上传

package cn.et.upload;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.FileUploadException;import org.apache.commons.fileupload.disk.DiskFileItemFactory;import org.apache.commons.fileupload.servlet.ServletFileUpload;/** * 文件上传 */public class UpaloadServlet extends HttpServlet {		protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {		response.setContentType("text/html");		String contextPath = request.getContextPath();//获取上下文路径		PrintWriter out = response.getWriter();		//接收文件		boolean isMultipart = ServletFileUpload.isMultipartContent(request);		//判断是否是文件上传请求		if(isMultipart){			//用于创建解析文件上传的工厂类			DiskFileItemFactory factory = new DiskFileItemFactory();						//默认上传文件 暂时存放在临时目录 System.getProperty("java.io.tmpdir");			//也有可能是tomcat/temp目录			//用于从请求中解析文件			ServletFileUpload upload = new ServletFileUpload(factory);			//设置字符集    解决文件名中文乱码问题			upload.setHeaderEncoding("UTF-8");			try {				//解析出文件的个数				List
    
      list = upload.parseRequest(request);				for(FileItem li:list){					//表示输入的文本框					if(li.isFormField()){						System.out.println(li.getFieldName()+"=>"+li.getString());					}else{//表示输入的是文件						//获取文件名						String fileName=li.getName();						InputStream is = li.getInputStream();						String destPath = "F:/file/"+fileName;						FileOutputStream fis = new FileOutputStream(destPath);						byte[] bt = new byte[1024];						int len = 0;						while((len=is.read(bt))!=-1){							fis.write(bt,0,len);						}						fis.close();						is.close();					}				}			} catch (FileUploadException e) {				e.printStackTrace();			}finally{				response.sendRedirect(contextPath+"/sud");			}		}		out.close();	}	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {		this.doGet(request, response);	}}

文件下载

package cn.et.download;import java.io.FileInputStream;import java.io.IOException;import java.io.OutputStream;import java.net.URLEncoder;import javax.servlet.ServletException;import javax.servlet.http.HttpServlet;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;/** * 文件下载 */public class DewnloadServlet extends HttpServlet {	public void doGet(HttpServletRequest request, HttpServletResponse response)			throws ServletException, IOException {		response.setContentType("text/html");		//文件下载的输出流		OutputStream os = response.getOutputStream();		//获取传递过的的文件名		String fileName = request.getParameter("fileName");		//告诉浏览器下载的文件名 		response.setHeader("Location", URLEncoder.encode(fileName,"UTF-8"));		response.setHeader("Content-Disposition", "attachment; filename="+URLEncoder.encode(fileName,"UTF-8"));		//将文件流 写入OutputSteam		FileInputStream fis = new FileInputStream("F:/file"+"/"+fileName);		byte[] bys = new byte[1024];		int len = 0;		while((len=fis.read(bys))!=-1){			os.write(bys, 0, len);			os.flush();		}		os.close();		fis.close(); 	}		public void doPost(HttpServletRequest request, HttpServletResponse response)			throws ServletException, IOException {		this.doPost(request, response);	}}

将文件夹里的文件获取出来，将显示在浏览器上

package cn.et.show;import java.io.File;import java.io.IOException;import java.util.ArrayList;import java.util.HashMap;import java.util.List;import java.util.Map;import javax.servlet.ServletException;import javax.servlet.http.HttpServlet;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;public class ShowUploadDownload extends HttpServlet {	public void doGet(HttpServletRequest request, HttpServletResponse response)			throws ServletException, IOException {		response.setContentType("text/html;charset=UTF-8");		File file = new File("F:/file");		File[] files = file.listFiles();		//设置样式		List
      
       > list = new ArrayList
       
        
         >();		for(File tfile:files){			Map
         
           map = new HashMap
          
           (); String name = tfile.getName(); map.put("name", name); list.add(map); } request.setAttribute("list", list); request.getRequestDispatcher("/index.jsp").forward(request, response); } public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { this.doGet(request, response); }}

示例：

访问ShowUploadDownload，将文件夹里的文件显示在浏览器上

上传文件

点击上传

下载文件点击下载

即会下载到C:\Users\Administrator\Downloads系统指定的下载目录下

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