java之上传文件、下载文件、下载网络文件

两种上传方式都可以
依赖pom.xml

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<!-- https://mvnrepository.com/artifact/commons-fileupload/commons-fileupload -->         <dependency>             <groupId>commons-fileupload</groupId>             <artifactId>commons-fileupload</artifactId>             <version>1.4</version>         </dependency>

 Spring bean配置

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<!--文件上传id必须=multipartResolver-->     <bean id="multipartResolver" class="org.springframework.web.multipart.commons.CommonsMultipartResolver">         <!--请求的编码格式，必须和jsp的pageEncoding属性一致，以便正确读取表单的内容，默认为ISO-8859-1-->         <property name="defaultEncoding" value="utf-8"/>         <!--上传文件大小上限，单位为字节10485760=10M-->         <property name="maxUploadSize" value="10485760"/>         <property name="maxInMemorySize" value="40960"/>     </bean>

 代码

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@PostMapping("/article/upload1Handler")     public String upload1Handler(@RequestParam("file") CommonsMultipartFile file, HttpServletRequest request) throws IOException {         String uploadFileName = file.getOriginalFilename();         if ("".equals(uploadFileName)){             return "redirect:/article/index";         }         System.out.println("上传文件名：" + uploadFileName);         String path = request.getServletContext().getRealPath("/upload");         File realPath = new File(path);         if (!realPath.exists()) {             realPath.mkdir();         }         System.out.println("上传文件地址：" + realPath);         InputStream is = file.getInputStream();//文件输入流         BufferedInputStream bis = new BufferedInputStream(is);         OutputStream os = new FileOutputStream(new File(realPath,uploadFileName));//文件输出流         BufferedOutputStream bos = new BufferedOutputStream(os);         byte[] buffer = new byte[1024];         int len = 0;         while ((len = is.read(buffer)) != -1) {             bos.write(buffer, 0, len);         }         bis.close();         bos.close();         return "redirect:/article/index";     }     @PostMapping("/article/upload2Handler")     public String upload2Handler(@RequestParam("file") CommonsMultipartFile file, HttpServletRequest request) throws IOException {         String path = request.getServletContext().getRealPath("/upload");         File realPath = new File(path);         if (!realPath.exists()) {             realPath.mkdir();         }         System.out.println("上传文件地址：" + realPath);         //通过CommonsMultipartFile的方法直接写文件         file.transferTo(new File(realPath + "/" + file.getOriginalFilename()));         return "redirect:/article/index";     }

 视图

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<form action="/article/upload2Handler" method="post" enctype="multipart/form-data">     <input type="file" name="file"/>     <button type="submit">Submit</button> </form>

 下载文件：

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@PostMapping("/article/downHandler")     public String downHandler(HttpServletResponse response, HttpServletRequest request) throws IOException {         String path = request.getServletContext().getRealPath("/upload");         String fileName = "1.png";         response.reset(); // 非常重要         response.setCharacterEncoding("UTF-8");         response.setContentType("multipart/form-data");//二进制传输数据         response.setHeader("Content-Disposition", "attachment; filename=" + URLEncoder.encode(fileName, "UTF-8"));         File file = new File(path, fileName);         InputStream is = new FileInputStream(file);         OutputStream os = response.getOutputStream();           BufferedInputStream bis = new BufferedInputStream(is);         BufferedOutputStream bos = new BufferedOutputStream(os);         byte[] buffer = new byte[1024];         int len = 0;         while ((len = is.read(buffer)) != -1) {             bos.write(buffer, 0, len);         }         bis.close();         bos.close();         return "redirect:/article/index";     }

下载网络文件：

package com.xcg.webapp.common;

import java.io.File;
import java.io.FileOutputStream;
import java.io.InputStream;
import java.net.URL;
import java.net.URLConnection;

public class DownloadUtil {
    /**
     * 下载网络文件
     * 测试下载文件 https://catalog.s.download.windowsupdate.com/d/msdownload/update/software/crup/2024/10/windows10.0-kb5044619-x64_3ef2399e39c2d708f26d02aeb985c2c7f53f9a2c.cab
     */
    public static void downloadNet(String webUrl) throws Exception{
        //总字节数
        int byteSum = 0;
        //每次读取的字节数
        int byteRead = 0;
        //网络地址
        URL url = new URL(webUrl);
        //网络文件名
        String fileName = new File(webUrl).getName();
        try {
            URLConnection conn = url.openConnection();
            InputStream inStream = conn.getInputStream();
            FileOutputStream fs = new FileOutputStream(fileName);
            byte[] buffer = new byte[1024];
            while ((byteRead = inStream.read(buffer)) != -1) {
                byteSum += byteRead;
                fs.write(buffer, 0, byteRead);
            }
            System.out.println("总字节数；" + byteSum);
        } catch (Exception e) {
            e.printStackTrace();
            throw e;
        }
    }
}

下载文件的几种方式：https://blog.csdn.net/longzhongxiaoniao/article/details/89295891