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Java大文件上传(分片上传+断点续传)的解决方案详解

2025-12-16 09:44:25 作者：悟空码字

大文件上传通常指上传超过几百MB甚至几个GB的文件,与普通文件上传相比,大文件上传会面临很多调整,下面小编就和大家详细讲讲具体的解决方案吧

什么是大文件上传

大文件上传通常指上传超过几百MB甚至几个GB的文件。与普通文件上传相比，大文件上传面临以下挑战：

内存限制 - 一次性加载整个文件到内存会导致内存溢出
网络稳定性 - 上传过程中网络中断需要能够断点续传
超时问题 - 长时间上传可能导致连接超时
进度监控 - 需要实时显示上传进度
文件校验 - 确保文件完整性和安全性

解决方案：分片上传

大文件上传的核心思想是将文件分割成多个小块，分别上传，最后在服务器端合并。

前端代码示例 (HTML + JavaScript)

<!DOCTYPE html>
<html>
<head>
    <title>大文件上传</title>
</head>
<body>
    <input type="file" id="fileInput" />
    <button onclick="uploadFile()">开始上传</button>
    <div id="progress"></div>

    <script>
        const CHUNK_SIZE = 2 * 1024 * 1024; // 2MB

        async function uploadFile() {
            const fileInput = document.getElementById('fileInput');
            const file = fileInput.files[0];
            
            if (!file) {
                alert('请选择文件');
                return;
            }

            const totalChunks = Math.ceil(file.size / CHUNK_SIZE);
            const fileMd5 = await calculateFileMD5(file);
            
            // 检查文件是否已上传过
            const checkResult = await checkFileExists(file.name, fileMd5, file.size);
            
            if (checkResult.uploaded) {
                alert('文件已存在');
                return;
            }

            let uploadedChunks = checkResult.uploadedChunks || [];

            for (let chunkIndex = 0; chunkIndex < totalChunks; chunkIndex++) {
                // 跳过已上传的分片
                if (uploadedChunks.includes(chunkIndex)) {
                    updateProgress(chunkIndex + 1, totalChunks);
                    continue;
                }

                const chunk = file.slice(chunkIndex * CHUNK_SIZE, (chunkIndex + 1) * CHUNK_SIZE);
                const formData = new FormData();
                formData.append('file', chunk);
                formData.append('chunkIndex', chunkIndex);
                formData.append('totalChunks', totalChunks);
                formData.append('fileName', file.name);
                formData.append('fileMd5', fileMd5);

                try {
                    await uploadChunk(formData);
                    updateProgress(chunkIndex + 1, totalChunks);
                } catch (error) {
                    console.error(`分片 ${chunkIndex} 上传失败:`, error);
                    alert('上传失败');
                    return;
                }
            }

            // 所有分片上传完成，请求合并
            await mergeChunks(file.name, fileMd5, totalChunks);
            alert('上传完成');
        }

        function uploadChunk(formData) {
            return fetch('/upload/chunk', {
                method: 'POST',
                body: formData
            }).then(response => {
                if (!response.ok) {
                    throw new Error('上传失败');
                }
                return response.json();
            });
        }

        function checkFileExists(fileName, fileMd5, fileSize) {
            return fetch(`/upload/check?fileName=${fileName}&fileMd5=${fileMd5}&fileSize=${fileSize}`)
                .then(response => response.json());
        }

        function mergeChunks(fileName, fileMd5, totalChunks) {
            return fetch('/upload/merge', {
                method: 'POST',
                headers: {
                    'Content-Type': 'application/json',
                },
                body: JSON.stringify({
                    fileName: fileName,
                    fileMd5: fileMd5,
                    totalChunks: totalChunks
                })
            }).then(response => response.json());
        }

        function updateProgress(current, total) {
            const progress = document.getElementById('progress');
            const percentage = Math.round((current / total) * 100);
            progress.innerHTML = `上传进度: ${percentage}%`;
        }

        // 计算文件MD5（简化版，实际应使用更可靠的库）
        async function calculateFileMD5(file) {
            // 这里使用简单的文件名+大小模拟MD5
            // 实际项目中应使用 spark-md5 等库
            return btoa(file.name + file.size).replace(/[^a-zA-Z0-9]/g, '');
        }
    </script>
</body>
</html>

后端Java代码示例 (Spring Boot)

配置文件上传设置

@Configuration
public class UploadConfig {
    
    @Bean
    public MultipartConfigElement multipartConfigElement() {
        MultipartConfigFactory factory = new MultipartConfigFactory();
        factory.setMaxFileSize("10GB");
        factory.setMaxRequestSize("10GB");
        return factory.createMultipartConfig();
    }
}

文件上传控制器

@RestController
@RequestMapping("/upload")
public class FileUploadController {
    
    @Value("${file.upload-dir:/tmp/uploads}")
    private String uploadDir;
    
    /**
     * 检查文件是否存在
     */
    @GetMapping("/check")
    public ResponseEntity<CheckResult> checkFile(
            @RequestParam String fileName,
            @RequestParam String fileMd5,
            @RequestParam Long fileSize) {
        
        String filePath = Paths.get(uploadDir, fileMd5, fileName).toString();
        File file = new File(filePath);
        
        CheckResult result = new CheckResult();
        
        // 如果文件已存在
        if (file.exists() && file.length() == fileSize) {
            result.setUploaded(true);
            return ResponseEntity.ok(result);
        }
        
        // 检查已上传的分片
        String chunkDir = getChunkDir(fileMd5);
        File chunkFolder = new File(chunkDir);
        if (!chunkFolder.exists()) {
            result.setUploaded(false);
            result.setUploadedChunks(new ArrayList<>());
            return ResponseEntity.ok(result);
        }
        
        List<Integer> uploadedChunks = Arrays.stream(chunkFolder.listFiles())
                .map(f -> Integer.parseInt(f.getName()))
                .collect(Collectors.toList());
        
        result.setUploaded(false);
        result.setUploadedChunks(uploadedChunks);
        return ResponseEntity.ok(result);
    }
    
    /**
     * 上传文件分片
     */
    @PostMapping("/chunk")
    public ResponseEntity<UploadResult> uploadChunk(
            @RequestParam("file") MultipartFile file,
            @RequestParam Integer chunkIndex,
            @RequestParam Integer totalChunks,
            @RequestParam String fileName,
            @RequestParam String fileMd5) {
        
        try {
            // 创建分片目录
            String chunkDir = getChunkDir(fileMd5);
            File chunkFolder = new File(chunkDir);
            if (!chunkFolder.exists()) {
                chunkFolder.mkdirs();
            }
            
            // 保存分片文件
            File chunkFile = new File(chunkDir + File.separator + chunkIndex);
            file.transferTo(chunkFile);
            
            UploadResult result = new UploadResult();
            result.setSuccess(true);
            result.setMessage("分片上传成功");
            return ResponseEntity.ok(result);
            
        } catch (Exception e) {
            UploadResult result = new UploadResult();
            result.setSuccess(false);
            result.setMessage("分片上传失败: " + e.getMessage());
            return ResponseEntity.status(HttpStatus.INTERNAL_SERVER_ERROR).body(result);
        }
    }
    
    /**
     * 合并文件分片
     */
    @PostMapping("/merge")
    public ResponseEntity<MergeResult> mergeChunks(@RequestBody MergeRequest request) {
        try {
            String chunkDir = getChunkDir(request.getFileMd5());
            String fileName = request.getFileName();
            String filePath = Paths.get(uploadDir, request.getFileMd5(), fileName).toString();
            
            // 创建目标文件
            File targetFile = new File(filePath);
            File parentDir = targetFile.getParentFile();
            if (!parentDir.exists()) {
                parentDir.mkdirs();
            }
            
            // 合并分片
            try (FileOutputStream fos = new FileOutputStream(targetFile)) {
                for (int i = 0; i < request.getTotalChunks(); i++) {
                    File chunkFile = new File(chunkDir + File.separator + i);
                    try (FileInputStream fis = new FileInputStream(chunkFile)) {
                        byte[] buffer = new byte[1024];
                        int len;
                        while ((len = fis.read(buffer)) > 0) {
                            fos.write(buffer, 0, len);
                        }
                    }
                    // 删除分片文件
                    chunkFile.delete();
                }
            }
            
            // 删除分片目录
            new File(chunkDir).delete();
            
            MergeResult result = new MergeResult();
            result.setSuccess(true);
            result.setMessage("文件合并成功");
            result.setFilePath(filePath);
            return ResponseEntity.ok(result);
            
        } catch (Exception e) {
            MergeResult result = new MergeResult();
            result.setSuccess(false);
            result.setMessage("文件合并失败: " + e.getMessage());
            return ResponseEntity.status(HttpStatus.INTERNAL_SERVER_ERROR).body(result);
        }
    }
    
    private String getChunkDir(String fileMd5) {
        return Paths.get(uploadDir, "chunks", fileMd5).toString();
    }
}

数据传输对象

@Data
public class CheckResult {
    private boolean uploaded;
    private List<Integer> uploadedChunks;
}

@Data
public class UploadResult {
    private boolean success;
    private String message;
}

@Data
public class MergeRequest {
    private String fileName;
    private String fileMd5;
    private Integer totalChunks;
}

@Data
public class MergeResult {
    private boolean success;
    private String message;
    private String filePath;
}

应用配置

# application.properties
spring.servlet.multipart.max-file-size=10GB
spring.servlet.multipart.max-request-size=10GB
file.upload-dir=/data/uploads

关键技术点

分片上传：将大文件分割成小块，分别上传
断点续传：记录已上传的分片，网络中断后可以从中断处继续
文件校验：通过MD5验证文件完整性
进度监控：实时显示上传进度
内存优化：流式处理，避免内存溢出

优化建议

增加重试机制：网络异常时自动重试
并行上传：同时上传多个分片提高速度
压缩传输：对分片进行压缩减少网络传输量
安全验证：添加身份验证和文件类型检查
分布式存储：支持分布式文件系统存储

这种方案可以有效解决大文件上传的各种问题，提供稳定可靠的上传体验。

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