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28. 文件上传和下载

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页面

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<%@ 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>
	<h3> 文件上传 </h3>
	<from action="FileUploadDemo" method="post" enctype="multipart/from-data">
		选择文件：<input type="file", name="fileupload"/>
		提交上传  <input type="submit", value="上传文件"/>
	</from>
</body>
</html>

上传文件

commons-fileupload 包依赖 common-io, 所以需要先导入这两个包。

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package com.itguigu.file;

import java.io.File;
import java.io.IOException;
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;


public class FileUploadDemo extends HttpServlet {
	private static final long serialVersionUID = 1L;

	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		// 获取上传到的文件夹的路径
		String uploadPath = this.getServletContext().getRealPath("/upload");
		
		// 1. 导包
		// 2. 创建工厂类
		DiskFileItemFactory diskFileItemFactory = new DiskFileItemFactory();
		// 3. 创建 ServletFileUpload 对象
		ServletFileUpload servletFileUpload = new ServletFileUpload(diskFileItemFactory);
		// 4. 解析参数 (parseRequest 返回一个List，里面是所有的参数，类型是 FileItem)
		try {
			List<FileItem> parseRequest = servletFileUpload.parseRequest(request);
			// 5. 迭代获取的所有参数，判断是否是文件
			for (FileItem fileItem : parseRequest) {
				if (fileItem.isFormField() == false) {
					// 6. 是文件，将其保存到 WebContent 下的 upload 文件夹下
					File file = new File(uploadPath +"/"+ fileItem.getName());
					fileItem.write(file);
				}
			}
		} catch (Exception e) {
			e.printStackTrace();
		}
		response.getWriter().write("success!");
	}

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

文件名相同

相同名称文件会被覆盖，使用 uuid 将文件变成唯一文件即可。

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String uuid = UUID.randomUUID().toString().replace("-", "");
File file = new File(uploadPath +"/"+ uuid + fileItem.getName());

限制文件大小

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// 设置单文件大小，单位是 B
servletFileUpload.setFileSizeMax(2*1024);
// 设置总文件的大小，单位是 B
// servletFileUpload.setSizeMax(sizeMax);

文件上传完整代码

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package com.itguigu.file;

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

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.FileUploadBase.FileSizeLimitExceededException;
import org.apache.commons.fileupload.FileUploadException;
import org.apache.commons.fileupload.disk.DiskFileItemFactory;
import org.apache.commons.fileupload.servlet.ServletFileUpload;


public class FileUploadDemo extends HttpServlet {
	private static final long serialVersionUID = 1L;

	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		response.setContentType("text/html;charset=UTF-8");
		request.setCharacterEncoding("UTF-8");
		// 获取上传到的文件夹的路径
		String uploadPath = this.getServletContext().getRealPath("/upload");
		
		// 1. 导包
		// 2. 创建工厂类
		DiskFileItemFactory diskFileItemFactory = new DiskFileItemFactory();
		// 3. 创建 ServletFileUpload 对象
		ServletFileUpload servletFileUpload = new ServletFileUpload(diskFileItemFactory);
		// 设置单文件大小，单位是 B
		servletFileUpload.setFileSizeMax(2*1024);
		// 设置总文件的大小，单位是 B
		// servletFileUpload.setSizeMax(sizeMax);
		// 4. 解析参数 (parseRequest 返回一个List，里面是所有的参数，类型是 FileItem)
		try {
			List<FileItem> parseRequest = servletFileUpload.parseRequest(request);
			// 5. 迭代获取的所有参数，判断是否是文件
			for (FileItem fileItem : parseRequest) {
				if (fileItem.isFormField() == false) {
					// 6. 是文件，将其保存到 WebContent 下的 upload 文件夹下
					String uuid = UUID.randomUUID().toString().replace("-", "");
					File file = new File(uploadPath +"/"+ uuid + fileItem.getName());
					fileItem.write(file);
				}
			}
			response.getWriter().write("文件上传失败!");
		} catch (FileSizeLimitExceededException e) {
			e.printStackTrace();
			response.getWriter().write("单文件大小不能超过 2k!");
		} catch (Exception e) {
			e.printStackTrace();
		}
	}

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

文件下载

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package com.itguigu.file;

import java.io.FileInputStream;
import java.io.IOException;
import java.net.URLEncoder;

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

import sun.misc.BASE64Encoder;


public class FileDownloadDemo extends HttpServlet {
	private static final long serialVersionUID = 1L;
       
	@SuppressWarnings("resource")
	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		request.setCharacterEncoding("UTF-8");

		// 获取文件名
		String filename = request.getParameter("filename");
		// 获取文件的真实路径
		String realPath = this.getServletContext().getRealPath("/WEB-INF/download");
		String downloadPath = realPath + "/" +filename;
		
		//设置浏览器响应体文件类型
		String mimeType = request.getServletContext().getMimeType(filename);
		response.setContentType(mimeType);
		//解决文件名中文乱码问题
		String header = request.getHeader("User-Agent");
		if(header != null && header.contains("Firefox")) {
			filename = "=?utf-8?B?"+new BASE64Encoder().encode(filename.getBytes("utf-8"))+"?=";
		}else {
			filename = URLEncoder.encode(filename, "UTF-8");
		}
		//设置浏览器响应体内容格式，为附件格式。(告诉浏览器别播放，下载)
		response.setHeader("Content-Disposition", "attachment; filename="+filename);
		
		// 读取资源，同时写到客户端
		FileInputStream fileInputStream = new FileInputStream(downloadPath);
		// 创建写出流
		ServletOutputStream outputStream = response.getOutputStream();
		byte[] b = new byte[1024];
		while (fileInputStream.read(b) != -1) {
			outputStream.write(b);
		}
		outputStream.close();
		fileInputStream.close();
	}

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