JavaWeb-文件的上传与下载

最新推荐文章于 2022-07-23 11:26:44 发布

原创最新推荐文章于 2022-07-23 11:26:44 发布 · 242 阅读

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一.文件的上传：

使用form表单提交并上传文件。
注意：encType = “multipart/form-data”;表单的method必须是post ; input 的 file 必须有 name 。

<%@page import="com.EzerbelCN.servlets.TempUtils"%>
<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<%@taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
<% %>
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Welcome ! Pictures Here !</title>
<style type="text/css">

	img{
		width:200px;
		height:120px;
	}
	
	.imgs{
		float:left;
		width:250px;
	}	
	
</style>

<% 
	application.setAttribute("ctp", request.getContextPath());
%>
</head>
<body>	
	<form action="${ctp}/upload" method="post" enctype="multipart/form-data">
		用户名：<input type="text" name="username"/><br/>
		头像：<input type="file" name="headerimg" accept="image/jpg,image/png"/><br/>
		<input type="submit" value="提交"><br/>
	</form>
	<hr/>
	<div>
		<c:forEach items="<%=TempUtils.getPaths()%>" var="path">
			<div class="imgs">
				<img src="/2.FileUpload/${path}"></img><br/>
				<!-- 不要在前面加 /-->
				<a href="download?file=${path}">下载图片</a>
			</div>
		</c:forEach>
	</div>
</body>
</html>

接受并处理post请求

借助commons-fileupload-1.3.1.jar、commons-io-2.2.jar可以快速实现对带有文件上传的表单解析。

package com.EzerbelCN.servlets;

import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.util.List;
import java.util.UUID;

import javax.servlet.ServletContext;
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 org.apache.commons.io.IOUtils;

public class UploadServlet extends HttpServlet {
	
	private static final long serialVersionUID = -6724597434450649221L;

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

	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		// 当前请求是否是一个多部件(文件上传)请求？
		boolean isMultipart = ServletFileUpload.isMultipartContent(request);
		if(isMultipart) {
			// Create a factory for disk-based file items
			DiskFileItemFactory factory = new DiskFileItemFactory();
			// Configure a repository (to ensure a secure temp location is used)
			ServletContext servletContext = this.getServletConfig().getServletContext();
			File repository = (File) servletContext.getAttribute("javax.servlet.context.tempdir");
			
			String realPath = servletContext.getRealPath("/pics");
			File repo =  new File(realPath);
			factory.setRepository(repo);
			
			System.out.println("pics realPath =============== " + realPath);
			
			// Create a new file upload handler
			ServletFileUpload upload = new ServletFileUpload(factory);
			//一个FileItem代表一个表单（form）项的详细信息
			try {
				// Parse the request
				List<FileItem> items = upload.parseRequest(request);
				System.out.println("items.size == " + items.size());
				
				for (FileItem fileItem : items) {
					if(!fileItem.isFormField()) {
						
						System.out.println("提交的表单 key = " + fileItem.getFieldName());
						System.out.println("上传的文件名 = " + fileItem.getName());
						
						// IE或Edge浏览器所get到的filename会带有路径，必须把路径去掉才行
						String fname = fileItem.getName();
						int lastIndexOf = fname.lastIndexOf("\\");
						fname = fname.substring(lastIndexOf+1);
						//加上UUID作为前缀防止重名
						fname = UUID.randomUUID().toString().replace("-", "")+fname;
						
						InputStream is = fileItem.getInputStream();
						FileOutputStream os = new FileOutputStream(realPath + "\\" + fname);
						//os.write(fileItem.get());
						System.out.println("fname == " + fname);
						System.out.println(realPath +"\\"+fname);
						IOUtils.copy(is, os);
						os.close();
						is.close();
						//存到一个类的静态成员List中用于后续下载使用
						TempUtils.AddImg("pics/"+fname);
					}else {
						System.out.println("普通表单项： key = " +  fileItem.getFieldName() + "  value= " + fileItem.getString() );
					}
				}
			} catch (FileUploadException e) {
				e.printStackTrace();
			}
		}
		request.getRequestDispatcher("/index.jsp").forward(request, response);
	}
}

配置web.xml

  <servlet>
    <servlet-name>UploadServlet</servlet-name>
    <servlet-class>com.EzerbelCN.servlets.UploadServlet</servlet-class>
  </servlet>
  <servlet-mapping>
    <servlet-name>UploadServlet</servlet-name>
    <url-pattern>/upload</url-pattern>
  </servlet-mapping>

测试

在这里插入图片描述

二.文件的下载

1）处理下载请求

package com.EzerbelCN.servlets;

import java.io.FileInputStream;
import java.io.IOException;
import java.util.UUID;

import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.ServletOutputStream;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.apache.commons.io.IOUtils;

public class DownloadServlet extends HttpServlet {

	private static final long serialVersionUID = 8980356474131595540L;

	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		System.out.println("Dooo Gettt");
		String file = request.getParameter("file");
		//1.servletContext用于获得真实路径
		ServletContext servletContext = this.getServletConfig().getServletContext();
		String realPath = servletContext.getRealPath(file);
		//截掉前面的路径
		int lastIndexOf = file.lastIndexOf("/");
		String fname = file.substring(lastIndexOf+1);
		//截掉前面的UUID
		int UIDLen = UUID.randomUUID().toString().replace("-", "").length();
		fname = fname.substring(UIDLen);
		
		//转换编码格式防止中文乱码，UTF8 -> GBK -> ISO-8859-1
		fname = new String(fname.getBytes("GBK"),"ISO-8859-1");
		//告诉浏览器这是一个附件，需要下载，不能直接在浏览器显示
		response.setHeader("Content-Disposition", "attachment;filename="+fname);
		
		System.out.println("file == " + file);
		System.out.println("fname == " + fname);
		
		System.out.println("realPath == " + realPath);
		//2.获得要下载的输入流
		FileInputStream fis = new FileInputStream(realPath);
		//3.获得输出流
		ServletOutputStream sos = response.getOutputStream();
		
		IOUtils.copy(fis, sos);
		sos.close();
		fis.close();
	}

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

}

配置web.xml

  <servlet>
  	<servlet-name>DownloadServlet</servlet-name>
  	<servlet-class>com.EzerbelCN.servlets.DownloadServlet</servlet-class>
  </servlet>
  <servlet-mapping>
  	<servlet-name>DownloadServlet</servlet-name>
  	<url-pattern>/download</url-pattern>
  </servlet-mapping>