使用Spring Boot实现大文件断点续传及文件校验

一、简介

随着互联网的快速发展，大文件的传输成为了互联网应用的重要组成部分。然而，由于网络不稳定等因素的影响，大文件的传输经常会出现中断的情况，这时需要重新传输，导致传输效率低下。

为了解决这个问题，可以实现大文件的断点续传功能。断点续传功能可以在传输中断后继续传输，而不需要从头开始传输。这样可以大大提高传输的效率。

Spring Boot是一个快速开发的Java Web开发框架，可以帮助我们快速搭建一个Web应用程序。在Spring Boot中，我们可以很容易地实现大文件的断点续传功能。

本文将介绍如何使用Spring Boot实现大文件的断点续传功能。

二、Spring Boot实现大文件断点续传的原理

实现大文件的断点续传功能，需要在客户端和服务端都进行相应的实现。

实现示例1

服务端如何将一个大视频文件做切分，分段响应给客户端，让浏览器可以渐进式地播放。

Spring Boot实现HTTP分片下载断点续传，从而实现H5页面的大视频播放问题，实现渐进式播放，每次只播放需要播放的内容就可以了，不需要加载整个文件到内存中。

文件的断点续传、文件多线程并发下载（迅雷就是这么玩的）等。

  <dependencyManagement><dependencies><dependency><groupId>cn.hutool</groupId><artifactId>hutool-bom</artifactId><version>5.8.18</version><type>pom</type><scope>import</scope></dependency></dependencies></dependencyManagement><dependencies><dependency><groupId>cn.hutool</groupId><artifactId>hutool-core</artifactId></dependency><dependency><groupId>org.projectlombok</groupId><artifactId>lombok</artifactId><optional>true</optional></dependency></dependencies>

代码实现

ResourceController

package com.example.insurance.controller;import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.util.List;import com.example.insurance.common.ContentRange;
import com.example.insurance.common.MediaContentUtil;
import com.example.insurance.common.NioUtils;
import lombok.extern.slf4j.Slf4j;
import org.springframework.http.HttpHeaders;
import org.springframework.http.HttpRange;
import org.springframework.http.HttpStatus;
import org.springframework.util.CollectionUtils;
import org.springframework.util.StopWatch;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestHeader;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;/*** 内容资源控制器*/
@SuppressWarnings("unused")
@Slf4j
@RestController("resourceController")
@RequestMapping(path = "/resource")
public class ResourceController {/*** 获取文件内容** @param fileName 内容文件名称* @param response 响应对象*/@GetMapping("/media/{fileName}")public void getMedia(@PathVariable String fileName, HttpServletRequest request, HttpServletResponse response,@RequestHeader HttpHeaders headers) {
//        printRequestInfo(fileName, request, headers);String filePath = MediaContentUtil.filePath();try {this.download(fileName, filePath, request, response, headers);} catch (Exception e) {log.error("getMedia error, fileName={}", fileName, e);}}/*** 获取封面内容** @param fileName 内容封面名称* @param response 响应对象*/@GetMapping("/cover/{fileName}")public void getCover(@PathVariable String fileName, HttpServletRequest request, HttpServletResponse response,@RequestHeader HttpHeaders headers) {
//        printRequestInfo(fileName, request, headers);String filePath = MediaContentUtil.filePath();try {this.download(fileName, filePath, request, response, headers);} catch (Exception e) {log.error("getCover error, fileName={}", fileName, e);}}// ======= internal =======private static void printRequestInfo(String fileName, HttpServletRequest request, HttpHeaders headers) {String requestUri = request.getRequestURI();String queryString = request.getQueryString();log.debug("file={}, url={}?{}", fileName, requestUri, queryString);log.info("headers={}", headers);}/*** 设置请求响应状态、头信息、内容类型与长度 等。* <pre>* <a href="https://www.rfc-editor.org/rfc/rfc7233">*     HTTP/1.1 Range Requests</a>* 2. Range Units* 4. Responses to a Range Request** <a href="https://www.rfc-editor.org/rfc/rfc2616.html">*     HTTP/1.1</a>* 10.2.7 206 Partial Content* 14.5 Accept-Ranges* 14.13 Content-Length* 14.16 Content-Range* 14.17 Content-Type* 19.5.1 Content-Disposition* 15.5 Content-Disposition Issues** <a href="https://www.rfc-editor.org/rfc/rfc2183">*     Content-Disposition</a>* 2. The Content-Disposition Header Field* 2.1 The Inline Disposition Type* 2.3 The Filename Parameter* </pre>** @param response     请求响应对象* @param fileName     请求的文件名称* @param contentType  内容类型* @param contentRange 内容范围对象*/private static void setResponse(HttpServletResponse response, String fileName, String contentType,ContentRange contentRange) {// http状态码要为206：表示获取部分内容response.setStatus(HttpStatus.PARTIAL_CONTENT.value());// 支持断点续传，获取部分字节内容// Accept-Ranges：bytes，表示支持Range请求response.setHeader(HttpHeaders.ACCEPT_RANGES, ContentRange.BYTES_STRING);// inline表示浏览器直接使用，attachment表示下载，fileName表示下载的文件名response.setHeader(HttpHeaders.CONTENT_DISPOSITION,"inline;filename=" + MediaContentUtil.encode(fileName));// Content-Range，格式为：[要下载的开始位置]-[结束位置]/[文件总大小]// Content-Range: bytes 0-10/3103，格式为bytes 开始-结束/全部response.setHeader(HttpHeaders.CONTENT_RANGE, contentRange.toContentRange());response.setContentType(contentType);// Content-Length: 11，本次内容的大小response.setContentLengthLong(contentRange.applyAsContentLength());}/*** <a href="https://www.jianshu.com/p/08db5ba3bc95">*     Spring Boot 处理 HTTP Headers</a>*/private void download(String fileName, String path, HttpServletRequest request, HttpServletResponse response,HttpHeaders headers)throws IOException {Path filePath = Paths.get(path + fileName);if (!Files.exists(filePath)) {log.warn("file not exist, filePath={}", filePath);return;}long fileLength = Files.size(filePath);
//        long fileLength2 = filePath.toFile().length() - 1;
//        // fileLength=1184856, fileLength2=1184855
//        log.info("fileLength={}, fileLength2={}", fileLength, fileLength2);// 内容范围ContentRange contentRange = applyAsContentRange(headers, fileLength, request);// 要下载的长度long contentLength = contentRange.applyAsContentLength();log.debug("contentRange={}, contentLength={}", contentRange, contentLength);// 文件类型String contentType = request.getServletContext().getMimeType(fileName);// mimeType=video/mp4, CONTENT_TYPE=nulllog.debug("mimeType={}, CONTENT_TYPE={}", contentType, request.getContentType());setResponse(response, fileName, contentType, contentRange);// 耗时指标统计StopWatch stopWatch = new StopWatch("downloadFile");stopWatch.start(fileName);try {// case-1.参考网上他人的实现
//            if (fileLength >= Integer.MAX_VALUE) {
//                NioUtils.copy(filePath, response, contentRange);
//            } else {
//                NioUtils.copyByChannelAndBuffer(filePath, response, contentRange);
//            }// case-2.使用现成APINioUtils.copyByBio(filePath, response, contentRange);
//            NioUtils.copyByNio(filePath, response, contentRange);// case-3.视频分段渐进式播放
//            if (contentType.startsWith("video")) {
//                NioUtils.copyForBufferSize(filePath, response, contentRange);
//            } else {
//                // 图片、PDF等文件
//                NioUtils.copyByBio(filePath, response, contentRange);
//            }} finally {stopWatch.stop();log.info("download file, fileName={}, time={} ms", fileName, stopWatch.getTotalTimeMillis());}}private static ContentRange applyAsContentRange(HttpHeaders headers, long fileLength, HttpServletRequest request) {/** 3.1. Range - HTTP/1.1 Range Requests* https://www.rfc-editor.org/rfc/rfc7233#section-3.1* Range: "bytes" "=" first-byte-pos "-" [ last-byte-pos ]** For example:* bytes=0-* bytes=0-499*/// Range：告知服务端，客户端下载该文件想要从指定的位置开始下载List<HttpRange> httpRanges = headers.getRange();String range = request.getHeader(HttpHeaders.RANGE);// httpRanges=[], range=null// httpRanges=[448135688-], range=bytes=448135688-log.debug("httpRanges={}, range={}", httpRanges, range);// 开始下载位置long firstBytePos;// 结束下载位置long lastBytePos;if (CollectionUtils.isEmpty(httpRanges)) {firstBytePos = 0;lastBytePos = fileLength - 1;} else {HttpRange httpRange = httpRanges.get(0);firstBytePos = httpRange.getRangeStart(fileLength);lastBytePos = httpRange.getRangeEnd(fileLength);}return new ContentRange(firstBytePos, lastBytePos, fileLength);}
}

NioUtils

package com.example.insurance.common;import javax.servlet.http.HttpServletResponse;
import java.io.BufferedOutputStream;
import java.io.InputStream;
import java.io.OutputStream;
import java.io.RandomAccessFile;
import java.nio.MappedByteBuffer;
import java.nio.channels.Channels;
import java.nio.channels.FileChannel;
import java.nio.file.Path;
import java.nio.file.StandardOpenOption;import cn.hutool.core.io.IORuntimeException;
import cn.hutool.core.io.IoUtil;
import cn.hutool.core.io.NioUtil;
import cn.hutool.core.io.StreamProgress;
import cn.hutool.core.io.unit.DataSize;
import lombok.extern.slf4j.Slf4j;
import org.apache.catalina.connector.ClientAbortException;/*** NIO相关工具封装，主要针对Channel读写、拷贝等封装*/
@Slf4j
public final class NioUtils {/*** 缓冲区大小 16KB** @see NioUtil#DEFAULT_BUFFER_SIZE* @see NioUtil#DEFAULT_LARGE_BUFFER_SIZE*/
//    private static final int BUFFER_SIZE = NioUtil.DEFAULT_MIDDLE_BUFFER_SIZE;private static final int BUFFER_SIZE = (int) DataSize.ofKilobytes(16L).toBytes();/*** <pre>* <a href="https://blog.csdn.net/qq_32099833/article/details/109703883">*     Java后端实现视频分段渐进式播放</a>* 服务端如何将一个大的视频文件做切分，分段响应给客户端，让浏览器可以渐进式地播放。* 文件的断点续传、文件多线程并发下载（迅雷就是这么玩的）等。** <a href="https://blog.csdn.net/qq_32099833/article/details/109630499">*     大文件分片上传前后端实现</a>* </pre>*/public static void copyForBufferSize(Path filePath, HttpServletResponse response, ContentRange contentRange) {String fileName = filePath.getFileName().toString();RandomAccessFile randomAccessFile = null;OutputStream outputStream = null;try {// 随机读文件randomAccessFile = new RandomAccessFile(filePath.toFile(), "r");// 移动访问指针到指定位置randomAccessFile.seek(contentRange.getStart());// 注意：缓冲区大小 2MB，视频加载正常；1MB时有部分视频加载失败int bufferSize = BUFFER_SIZE;//获取响应的输出流outputStream = new BufferedOutputStream(response.getOutputStream(), bufferSize);// 每次请求只返回1MB的视频流byte[] buffer = new byte[bufferSize];int len = randomAccessFile.read(buffer);//设置此次相应返回的数据长度response.setContentLength(len);// 将这1MB的视频流响应给客户端outputStream.write(buffer, 0, len);log.info("file download complete, fileName={}, contentRange={}",fileName, contentRange.toContentRange());} catch (ClientAbortException | IORuntimeException e) {// 捕获此异常表示用户停止下载log.warn("client stop file download, fileName={}", fileName);} catch (Exception e) {log.error("file download error, fileName={}", fileName, e);} finally {IoUtil.close(outputStream);IoUtil.close(randomAccessFile);}}/*** 拷贝流，拷贝后关闭流。** @param filePath     源文件路径* @param response     请求响应* @param contentRange 内容范围*/public static void copyByBio(Path filePath, HttpServletResponse response, ContentRange contentRange) {String fileName = filePath.getFileName().toString();InputStream inputStream = null;OutputStream outputStream = null;try {RandomAccessFile randomAccessFile = new RandomAccessFile(filePath.toFile(), "r");randomAccessFile.seek(contentRange.getStart());inputStream = Channels.newInputStream(randomAccessFile.getChannel());outputStream = new BufferedOutputStream(response.getOutputStream(), BUFFER_SIZE);StreamProgress streamProgress = new StreamProgressImpl(fileName);long transmitted = IoUtil.copy(inputStream, outputStream, BUFFER_SIZE, streamProgress);log.info("file download complete, fileName={}, transmitted={}", fileName, transmitted);} catch (ClientAbortException | IORuntimeException e) {// 捕获此异常表示用户停止下载log.warn("client stop file download, fileName={}", fileName);} catch (Exception e) {log.error("file download error, fileName={}", fileName, e);} finally {IoUtil.close(outputStream);IoUtil.close(inputStream);}}/*** 拷贝流，拷贝后关闭流。* <pre>* <a href="https://www.cnblogs.com/czwbig/p/10035631.html">*     Java NIO 学习笔记（一）----概述，Channel/Buffer</a>* </pre>** @param filePath     源文件路径* @param response     请求响应* @param contentRange 内容范围*/public static void copyByNio(Path filePath, HttpServletResponse response, ContentRange contentRange) {String fileName = filePath.getFileName().toString();InputStream inputStream = null;OutputStream outputStream = null;try {RandomAccessFile randomAccessFile = new RandomAccessFile(filePath.toFile(), "r");randomAccessFile.seek(contentRange.getStart());inputStream = Channels.newInputStream(randomAccessFile.getChannel());outputStream = new BufferedOutputStream(response.getOutputStream(), BUFFER_SIZE);StreamProgress streamProgress = new StreamProgressImpl(fileName);long transmitted = NioUtil.copyByNIO(inputStream, outputStream,BUFFER_SIZE, streamProgress);log.info("file download complete, fileName={}, transmitted={}", fileName, transmitted);} catch (ClientAbortException | IORuntimeException e) {// 捕获此异常表示用户停止下载log.warn("client stop file download, fileName={}", fileName);} catch (Exception e) {log.error("file download error, fileName={}", fileName, e);} finally {IoUtil.close(outputStream);IoUtil.close(inputStream);}}/*** <pre>* <a href="https://blog.csdn.net/lovequanquqn/article/details/104562945">*     SpringBoot Java实现Http方式分片下载断点续传+实现H5大视频渐进式播放</a>* SpringBoot 实现Http分片下载断点续传，从而实现H5页面的大视频播放问题，实现渐进式播放，每次只播放需要播放的内容就可以了，不需要加载整个文件到内存中。* 二、Http分片下载断点续传实现* 四、缓存文件定时删除任务* </pre>*/public static void copy(Path filePath, HttpServletResponse response, ContentRange contentRange) {String fileName = filePath.getFileName().toString();// 要下载的长度long contentLength = contentRange.applyAsContentLength();BufferedOutputStream outputStream = null;RandomAccessFile randomAccessFile = null;// 已传送数据大小long transmitted = 0;try {randomAccessFile = new RandomAccessFile(filePath.toFile(), "r");randomAccessFile.seek(contentRange.getStart());outputStream = new BufferedOutputStream(response.getOutputStream(), BUFFER_SIZE);// 把数据读取到缓冲区中byte[] buffer = new byte[BUFFER_SIZE];int len = BUFFER_SIZE;//warning：判断是否到了最后不足4096（buffer的length）个byte这个逻辑（(transmitted + len) <= contentLength）要放前面//不然会会先读取randomAccessFile，造成后面读取位置出错;while ((transmitted + len) <= contentLength && (len = randomAccessFile.read(buffer)) != -1) {outputStream.write(buffer, 0, len);transmitted += len;log.info("fileName={}, transmitted={}", fileName, transmitted);}//处理不足buffer.length部分if (transmitted < contentLength) {len = randomAccessFile.read(buffer, 0, (int) (contentLength - transmitted));outputStream.write(buffer, 0, len);transmitted += len;log.info("fileName={}, transmitted={}", fileName, transmitted);}log.info("file download complete, fileName={}, transmitted={}", fileName, transmitted);} catch (ClientAbortException e) {// 捕获此异常表示用户停止下载log.warn("client stop file download, fileName={}, transmitted={}", fileName, transmitted);} catch (Exception e) {log.error("file download error, fileName={}, transmitted={}", fileName, transmitted, e);} finally {IoUtil.close(outputStream);IoUtil.close(randomAccessFile);}}/*** 通过数据传输通道和缓冲区读取文件数据。* <pre>* 当文件长度超过{@link Integer#MAX_VALUE}时，* 使用{@link FileChannel#map(FileChannel.MapMode, long, long)}报如下异常。* java.lang.IllegalArgumentException: Size exceeds Integer.MAX_VALUE*   at sun.nio.ch.FileChannelImpl.map(FileChannelImpl.java:863)*   at com.example.insurance.controller.ResourceController.download(ResourceController.java:200)* </pre>** @param filePath     源文件路径* @param response     请求响应* @param contentRange 内容范围*/public static void copyByChannelAndBuffer(Path filePath, HttpServletResponse response, ContentRange contentRange) {String fileName = filePath.getFileName().toString();// 要下载的长度long contentLength = contentRange.applyAsContentLength();BufferedOutputStream outputStream = null;FileChannel inChannel = null;// 已传送数据大小long transmitted = 0;long firstBytePos = contentRange.getStart();long fileLength = contentRange.getLength();try {inChannel = FileChannel.open(filePath, StandardOpenOption.READ, StandardOpenOption.WRITE);// 建立直接缓冲区MappedByteBuffer inMap = inChannel.map(FileChannel.MapMode.READ_ONLY, firstBytePos, fileLength);outputStream = new BufferedOutputStream(response.getOutputStream(), BUFFER_SIZE);// 把数据读取到缓冲区中byte[] buffer = new byte[BUFFER_SIZE];int len = BUFFER_SIZE;// warning：判断是否到了最后不足4096（buffer的length）个byte这个逻辑（(transmitted + len) <= contentLength）要放前面// 不然会会先读取file，造成后面读取位置出错while ((transmitted + len) <= contentLength) {inMap.get(buffer);outputStream.write(buffer, 0, len);transmitted += len;log.info("fileName={}, transmitted={}", fileName, transmitted);}// 处理不足buffer.length部分if (transmitted < contentLength) {len = (int) (contentLength - transmitted);buffer = new byte[len];inMap.get(buffer);outputStream.write(buffer, 0, len);transmitted += len;log.info("fileName={}, transmitted={}", fileName, transmitted);}log.info("file download complete, fileName={}, transmitted={}", fileName, transmitted);} catch (ClientAbortException e) {// 捕获此异常表示用户停止下载log.warn("client stop file download, fileName={}, transmitted={}", fileName, transmitted);} catch (Exception e) {log.error("file download error, fileName={}, transmitted={}", fileName, transmitted, e);} finally {IoUtil.close(outputStream);IoUtil.close(inChannel);}}}

ContentRange

package com.example.insurance.common;import lombok.AllArgsConstructor;
import lombok.Getter;/*** 内容范围对象* <pre>* <a href="https://www.rfc-editor.org/rfc/rfc7233#section-4.2">*     4.2. Content-Range - HTTP/1.1 Range Requests</a>* Content-Range: "bytes" first-byte-pos "-" last-byte-pos  "/" complete-length** For example:* Content-Range: bytes 0-499/1234* </pre>** @see org.apache.catalina.servlets.DefaultServlet.Range*/
@Getter
@AllArgsConstructor
public class ContentRange {/*** 第一个字节的位置*/private final long start;/*** 最后一个字节的位置*/private long end;/*** 内容完整的长度/总长度*/private final long length;public static final String BYTES_STRING = "bytes";/*** 组装内容范围的响应头。* <pre>* <a href="https://www.rfc-editor.org/rfc/rfc7233#section-4.2">*     4.2. Content-Range - HTTP/1.1 Range Requests</a>* Content-Range: "bytes" first-byte-pos "-" last-byte-pos  "/" complete-length** For example:* Content-Range: bytes 0-499/1234* </pre>** @return 内容范围的响应头*/public String toContentRange() {return BYTES_STRING + ' ' + start + '-' + end + '/' + length;
//        return "bytes " + start + "-" + end + "/" + length;}/*** 计算内容完整的长度/总长度。** @return 内容完整的长度/总长度*/public long applyAsContentLength() {return end - start + 1;}/*** Validate range.** @return true if the range is valid, otherwise false*/public boolean validate() {if (end >= length) {end = length - 1;}return (start >= 0) && (end >= 0) && (start <= end) && (length > 0);}@Overridepublic String toString() {return "firstBytePos=" + start +", lastBytePos=" + end +", fileLength=" + length;}
}

StreamProgressImpl

package com.example.insurance.common;import cn.hutool.core.io.StreamProgress;
import lombok.AllArgsConstructor;
import lombok.extern.slf4j.Slf4j;/*** 数据流进度条*/
@Slf4j
@AllArgsConstructor
public class StreamProgressImpl implements StreamProgress {private final String fileName;@Overridepublic void start() {log.info("start progress {}", fileName);}@Overridepublic void progress(long total, long progressSize) {log.debug("progress {}, total={}, progressSize={}", fileName, total, progressSize);}@Overridepublic void finish() {log.info("finish progress {}", fileName);}
}

MediaContentUtil

package com.example.insurance.common;import java.net.URLDecoder;
import java.net.URLEncoder;
import java.nio.charset.StandardCharsets;/*** 文件内容辅助方法集*/
public final class MediaContentUtil {public static String filePath() {String osName = System.getProperty("os.name");String filePath = "/data/files/";if (osName.startsWith("Windows")) {filePath = "D:\" + filePath;}
//        else if (osName.startsWith("Linux")) {
//            filePath = MediaContentConstant.FILE_PATH;
//        }else if (osName.startsWith("Mac") || osName.startsWith("Linux")) {filePath = "/home/admin" + filePath;}return filePath;}public static String encode(String fileName) {return URLEncoder.encode(fileName, StandardCharsets.UTF_8);}public static String decode(String fileName) {return URLDecoder.decode(fileName, StandardCharsets.UTF_8);}
}

实现示例2

代码实现

（1）客户端需要实现以下功能：

建立连接：客户端需要连接服务端，并建立连接。
分块传输文件：客户端需要将文件分成若干块，并逐块传输。在传输中，每个块传输完成后，需要将已传输的位置发送给服务端，以便服务端记录传输位置。
计算MD5值：在传输完成后，客户端需要计算文件的MD5值，以确保传输的完整性。
与服务端比较MD5值：在计算出MD5值后，客户端需要将MD5值发送给服务端，并与服务端返回的MD5值比较，以确保传输的完整性。

（2）服务端需要实现以下功能：

建立连接：服务端需要等待客户端连接，并建立连接。
接收文件：服务端需要接收客户端传输的文件。在接收文件时，需要记录传输的位置，并在传输中断后继续接收文件。
计算MD5值：在接收完成后，服务端需要计算文件的MD5值，以确保传输的完整性。
返回MD5值：在计算出MD5值后，服务端需要将MD5值返回给客户端。

1.编写客户端代码

在客户端中，我们需要实现以下功能：

建立连接：使用Java的Socket类建立与服务端的连接。
分块传输文件：将文件分成若干块，并逐块传输。在传输中，每个块传输完成后，需要将已传输的位置发送给服务端，以便服务端记录传输位置。
计算MD5值：在传输完成后，计算文件的MD5值，以确保传输的完整性。
与服务端比较MD5值：将MD5值发送给服务端，并与服务端返回的MD5值比较，以确保传输的完整性。

以下是客户端代码的实现：

@RestController
@RequestMapping("/file")
public class FileController {@PostMapping("/upload")public ResponseEntity<?> uploadFile(@RequestParam("file") MultipartFile file,@RequestParam("fileName") String fileName,@RequestParam("startPosition") long startPosition) {try {            // 建立连接Socket socket = new Socket("localhost", 8080);OutputStream outputStream = socket.getOutputStream();ObjectOutputStream objectOutputStream = new ObjectOutputStream(outputStream);// 分块传输文件FileInputStream fileInputStream = (FileInputStream) file.getInputStream();fileInputStream.skip(startPosition);byte[] buffer = new byte[1024];int len;while ((len = fileInputStream.read(buffer)) != -1) {outputStream.write(buffer, 0, len);}// 计算MD5值fileInputStream.getChannel().position(0);String md5 = DigestUtils.md5Hex(fileInputStream);// 与服务端比较MD5值InputStream inputStream = socket.getInputStream();ObjectInputStream objectInputStream = new ObjectInputStream(inputStream);String serverMd5 = (String) objectInputStream.readObject();if (!md5.equals(serverMd5)) {throw new RuntimeException("MD5值不匹配");}// 关闭连接objectOutputStream.close();outputStream.close();socket.close();} catch (Exception e) {e.printStackTrace();return ResponseEntity.status(HttpStatus.INTERNAL_SERVER_ERROR).body(e.getMessage());}return ResponseEntity.ok().build();}
}

2.编写服务端代码

在服务端中，我们需要实现以下功能：

建立连接：使用Java的ServerSocket类等待客户端连接，并建立连接。
接收文件：接收客户端传输的文件。在接收文件时，需要记录传输的位置，并在传输中断后继续接收文件。
计算MD5值：在接收完成后，计算文件的MD5值，以确保传输的完整性。
返回MD5值：将MD5值返回给客户端。

以下是服务端代码的实现：

@RestController
@RequestMapping("/file")
public class FileController {private final String FILE_PATH = "/tmp/upload/";@PostMapping("/upload")public ResponseEntity<?> uploadFile(HttpServletRequest request, @RequestParam("fileName") String fileName) {try {// 建立连接            ServerSocket serverSocket = new ServerSocket(8080);Socket socket = serverSocket.accept();InputStream inputStream = socket.getInputStream();ObjectInputStream objectInputStream = new ObjectInputStream(inputStream);// 接收文件            String filePath = FILE_PATH + fileName;RandomAccessFile randomAccessFile = new RandomAccessFile(filePath, "rw");long startPosition = randomAccessFile.length();randomAccessFile.seek(startPosition);byte[] buffer = new byte[1024];int len;while ((len = inputStream.read(buffer)) != -1) {randomAccessFile.write(buffer, 0, len);}   // 计算MD5值        FileInputStream fileInputStream = new FileInputStream(filePath);String md5 = DigestUtils.md5Hex(fileInputStream);// 返回MD5值        OutputStream outputStream = socket.getOutputStream();ObjectOutputStream objectOutputStream = new ObjectOutputStream(outputStream);objectOutputStream.writeObject(md5);        // 关闭连objectInputStream.close();inputStream.close();randomAccessFile.close();socket.close();serverSocket.close();} catch (Exception e) {e.printStackTrace();return ResponseEntity.status(HttpStatus.INTERNAL_SERVER_ERROR).body(e.getMessage());}return ResponseEntity.ok().build();}
}

3. 编写前端代码

在前端中，我们需要实现以下功能：

选择文件：提供一个文件选择框，让用户选择要上传的文件。
分块上传：将文件分块上传到服务器。在上传过程中，需要记录上传的位置，并在上传中断后继续上传。

以下是前端代码的实现：

<html>
<head><meta charset="UTF-8"><title>Spring Boot File Upload</title><script src="https://cdn.bootcss.com/jquery/3.3.1/jquery.min.js"></script>
</head>
<body><input type="file" id="file">
<button onclick="upload()">Upload</button>
<script>    var file;
var startPosition = 0;
$('#file').on('change', function () {file = this.files[0];
});function upload() {if (!file) {alert('Please select a file!');return;}var formData = new FormData();formData.append('file', file);formData.append('fileName', file.name);formData.append('startPosition', startPosition);$.ajax({url: '/file/upload',type: 'post',data: formData,cache: false,processData: false,contentType: false,success: function () {alert('Upload completed!');},error: function (xhr) {alert(xhr.responseText);},xhr: function () {var xhr = $.ajaxSettings.xhr();xhr.upload.onprogress = function (e) {if (e.lengthComputable) {var percent = e.loaded / e.total * 100;console.log('Upload percent: ' + percent.toFixed(2) + '%');}};return xhr;}});
}</script>
</body>
</html>