使用Servlet实现文件的上传与下载

太过爱你忘了你带给我的痛 2022-07-12 05:44 214阅读 0赞

一、新建JavaWeb项目

File->New->Other->Dynamic Web Project

二、新建UploadDownloadServlet

package com.cc.uploaddownload;
    
    import java.io.File;
    import java.io.FileInputStream;
    import java.io.IOException;
    import java.io.InputStream;
    import java.io.OutputStream;
    
    import javax.servlet.RequestDispatcher;
    import javax.servlet.ServletException;
    import javax.servlet.annotation.MultipartConfig;
    import javax.servlet.http.HttpServlet;
    import javax.servlet.http.HttpServletRequest;
    import javax.servlet.http.HttpServletResponse;
    import javax.servlet.http.Part;
    
    @MultipartConfig
    public class UploadDownloadServlet extends HttpServlet {
    
    	@Override
    	protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
    		// TODO Auto-generated method stub
    		doPost(req, resp);
    	}
    
    	@Override
    	protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
    		// TODO Auto-generated method stub
    		String method = req.getParameter("method");
    		if (method.equals("download")) {
    			this.download(req,resp);
    		}
    		if (method.equals("upload")) {
    			this.upload(req, resp);
    		}
    	}
    
    	@Override
    	public void destroy() {
    		// TODO Auto-generated method stub
    		super.destroy();
    	}
    
    	@Override
    	public void init() throws ServletException {
    		// TODO Auto-generated method stub
    		super.init();
    	}
    
    	private void upload(HttpServletRequest request, HttpServletResponse response) throws IOException, ServletException {
    		request.setCharacterEncoding("UTF-8");
    		response.setCharacterEncoding("text/html;charset=UTF-8");
    		// 获取上传文件域
    		Part part = request.getPart("headShot");
    		// 获取上传文件名称
    		String fileName = part.getSubmittedFileName();
    		// 为防止上传文件重名，对文件重新命名
    		String newFileName = System.currentTimeMillis() + fileName.substring(fileName.lastIndexOf("."));
    		// 将上传的文件保存在服务器发布路径的application/images路径下
    		// String filePath =
    		// getServletContext().getRealPath("/application/images");
    		String filePath = "D:/application/files";
    		System.out.println(filePath);
    		File f = new File(filePath);
    		if (!f.exists()) {
    			f.mkdirs();
    		}
    		part.write(filePath + "/" + newFileName);
    		RequestDispatcher dispatcher = request.getRequestDispatcher("updown.jsp");
    		dispatcher.forward(request, response);
    
    	}
    
    	private void download(HttpServletRequest request, HttpServletResponse response)
    			throws IOException, ServletException {
    		//得到工程的绝对路径  http://localhost:8080/UpDown
    //		String path = request.getServletContext().getRealPath("/")+"images\\";
    //		String path1 = request.getServletContext().getContextPath();
    //		String path2 = request.getServletPath();
    //		String path3 = request.getRequestURI();
    //		System.out.println(path);
    //		System.out.println("2:"+path1);
    //		System.out.println("3:"+path2);
    //		System.out.println("4:"+path3);
    		
    		String filename = "file.png";
    		File file = new File("D:\\application\\files\\1.png");
    		if (file.exists()) {
    			response.setContentType("application/x-msdownload");
    			response.setHeader("Content-Disposition", "attachment;filename=\"" + filename + "\"");
    			InputStream inputStream = new FileInputStream(file);
    			OutputStream outputStream = response.getOutputStream();
    			byte[] b = new byte[1024]; 
    			int n ;
    			while((n = inputStream.read(b))!=-1){
    				outputStream.write(b, 0, n);
    			}
    			outputStream.close();
    			inputStream.close();
    		}else{
    			RequestDispatcher dispatcher = request.getRequestDispatcher("updown.jsp");
    			dispatcher.forward(request, response);
    		}
    	}
    
    }

三、在web.xml添加servlet的映射

<?xml version="1.0" encoding="UTF-8"?>
    <web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://xmlns.jcp.org/xml/ns/javaee" xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd" version="3.1">
      <display-name>DownLoadUpLoad</display-name>
      
        <servlet>
        <servlet-name>UploadDownloadServlet</servlet-name>
        <servlet-class>com.cc.uploaddownload.UploadDownloadServlet</servlet-class>
      </servlet>
    
      <servlet-mapping>
        <servlet-name>UploadDownloadServlet</servlet-name>
        <url-pattern>/UploadDownloadServlet</url-pattern>
      </servlet-mapping>
    </web-app>

三、新建updown.jsp

<%@ page language="java" contentType="text/html; charset=GB18030"
    	pageEncoding="GB18030"%>
    <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
    
    <%
    	String path = request.getContextPath();
    	String basePath = request.getScheme() + "://" + request.getServerName() + ":" + request.getServerPort()
    			+ path + "/";
    %>
    <html>
    <head>
    <base href="<%=basePath%>">
    <title>Insert title here</title>
    </head>
    <body>
    	<form action="UploadDownloadServlet?method=upload" method="post"
    		enctype="multipart/form-data">
    		<input name="headShot" id="headShot" type="file"> <input
    			type="submit" value="提交">
    	</form>
    	<br /> 下载：
    	<a href="UploadDownloadServlet?method=download">图片</a>
    </body>
    </html>

四、 Run As->Run on Server

运行时需要在D:\\application\\files 目录下添加一个1.png文件以便下载

工程源码[http://download.csdn.net/detail/lrici/9753612][http_download.csdn.net_detail_lrici_9753612]

[http_download.csdn.net_detail_lrici_9753612]: http://download.csdn.net/detail/lrici/9753612