JavaWeb实现文件的上传与下载_Java教程

JavaWeb实现文件的上传与下载，供大家参考，具体内容如下

第一步：导包

导入commons-fileupload-1.3.3.jar和commons-io-2.4.jar两个依赖包

第二步：编写前端页面

1、提交页面 index.jsp

				?

									<%@ page language="java" contentType="text/html; charset=UTF-8"

									 pageEncoding="UTF-8"%>

									<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c"%>

									<!DOCTYPE html>

									<html>

									 <head>

									 <meta charset="UTF-8">

									 <title>Insert title here</title>

									 </head>

									 <body>

									 <form action="${pageContext.request.contextPath }/fileUpload" method="post" enctype="multipart/form-data">

									 头像：<input type="file" name="img" accept="image/*"/>

									 <input type="submit" value="提交"/>

									 </form>

									 </body>

									</html>

2、结果页面 result.jsp

				?

									<%@ page language="java" contentType="text/html; charset=UTF-8"

									 pageEncoding="UTF-8"%>

									<!DOCTYPE html>

									<html>

									<head>

									<meta charset="UTF-8">

									<title>Insert title here</title>

									</head>

									<body>

									 <center>

									 <a href="${pageContext.request.contextPath }/download?filename=${filename}" >

									 <img alt="xx" src="${src }">

									 </a>

									 </center>

									</body>

									</html>

第三步：编写上传和下载代码

1、上传图片 fileUpload.java

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									package cn.yz123123.controller;

									import java.io.File;

									import java.io.FileOutputStream;

									import java.io.IOException;

									import java.io.InputStream;

									import javax.servlet.ServletException;

									import javax.servlet.annotation.MultipartConfig;

									import javax.servlet.annotation.WebServlet;

									import javax.servlet.http.HttpServlet;

									import javax.servlet.http.HttpServletRequest;

									import javax.servlet.http.HttpServletResponse;

									import javax.servlet.http.Part;

									@WebServlet("/fileUpload")

									@MultipartConfig

									public class fileUpload extends HttpServlet {

									 private static final long serialVersionUID = 1L;

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

									 doPost(request, response);

									 }

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

									 //String username = request.getParameter("username");

									 Part part = request.getPart("img");

									 //获取文件的真实名称

									 String header = part.getHeader("content-disposition");

									 String realName = header.substring(header.indexOf("filename=")+10, header.length()-1);

									 //获取文件自身流

									 InputStream inputStream = part.getInputStream();

									 //获取file真实路径，如果没有则创建

									 String dir = request.getServletContext().getRealPath("/file/");

									 File dirFile = new File(dir);

									 //上面只是实例化了一个对象，并没有真正的创建一个文件夹

									 if (!dirFile.exists()) {

									 dirFile.mkdirs();

									 }

									 //创建文件对象，并用流的形式写在相应的文件夹中

									 File file = new File(dir, realName);

									 FileOutputStream fileOutputStream = new FileOutputStream(file);

									 byte[] buf = new byte[1024];

									 int len;

									 while((len=inputStream.read(buf))!=-1) {

									 fileOutputStream.write(buf, 0, len);

									 }

									 fileOutputStream.close();

									 inputStream.close();

									 //以下为测试

									 request.setAttribute("src", request.getContextPath()+"/file/"+realName);

									 request.setAttribute("filename", realName);

									 request.getRequestDispatcher("/result.jsp").forward(request, response);

									 }

									}

2、下载图片 fileDownload.java

				?

									package cn.yz123123.controller;

									import java.io.FileInputStream;

									import java.io.IOException;

									import java.util.UUID;

									import javax.servlet.ServletException;

									import javax.servlet.ServletOutputStream;

									import javax.servlet.annotation.WebServlet;

									import javax.servlet.http.HttpServlet;

									import javax.servlet.http.HttpServletRequest;

									import javax.servlet.http.HttpServletResponse;

									@WebServlet(urlPatterns = "/download")

									public class fileDownload extends HttpServlet{

									 @Override

									 protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {

									 String filename = req.getParameter("filename");

									 //获取文件的真实路径

									 String filePath = req.getServletContext().getRealPath("/file/"+filename);

									 FileInputStream fileInputStream = new FileInputStream(filePath);

									 resp.setCharacterEncoding("UTF-8");

									 resp.setHeader("Content-Disposition","attachment;filename="+UUID.randomUUID()+filename);

									 ServletOutputStream outputStream = resp.getOutputStream();

									 byte[] buf = new byte[1024];

									 int len;

									 while((len=fileInputStream.read(buf))!=-1) {

									 outputStream.write(buf, 0, len);

									 }

									 outputStream.close();

									 fileInputStream.close();

									 }

									 @Override

									 protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {

									 super.doGet(req, resp);

									 }

									}