大文件的分片上传和断点上传

一、大文件的分片上传

html 复制代码

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Chunked File Upload</title>
</head>
<body>
    <input type="file" id="fileInput">
    <button onclick="uploadFile()">Upload</button>

    <script>
        const chunkSize = 1024 * 1024; // 每个分片大小为1MB
        let file;
        let chunks = [];

        document.getElementById('fileInput').addEventListener('change', function(event) {
            file = event.target.files[0];
        });

        function uploadFile() {
            if (!file) {
                console.error('Please select a file.');
                return;
            }

            let fileSize = file.size;
            let numberOfChunks = Math.ceil(fileSize / chunkSize);

            for (let i = 0; i < numberOfChunks; i++) {
                let start = i * chunkSize;
                let end = Math.min(fileSize, start + chunkSize);
                let chunk = file.slice(start, end);
                chunks.push(chunk);
            }

            // 模拟分片上传
            uploadChunks(chunks);
        }

        function uploadChunks(chunks) {
            let currentChunk = 0;

            function uploadNextChunk() {
                if (currentChunk < chunks.length) {
                    let formData = new FormData();
                    formData.append('chunk', chunks[currentChunk]);
                    formData.append('totalChunks', chunks.length);
                    formData.append('chunkIndex', currentChunk);

                    // 发送分片数据给后端进行处理
                    // 这里可以使用fetch或者其他Ajax库发送请求

                    currentChunk++;
                    // 模拟延迟，实际应用中需要根据网络情况设置合适的延迟
                    setTimeout(uploadNextChunk, 1000);
                } else {
                    console.log('File upload complete!');
                }
            }

            uploadNextChunk();
        }
    </script>
</body>
</html>

在这个示例中，首先通过<input type="file">元素让用户选择要上传的文件，然后在点击"Upload"按钮时触发uploadFile()函数，该函数会将文件按照指定大小切分成多个分片，并调用uploadChunks()函数模拟分片上传过程。

二、大文件分片上传结合断点上传

前端将文件分片并逐个上传到后端，同时后端需要保存已上传的分片信息，以便在中断后能够恢复上传。以下是一个简单的示例，展示如何实现大文件的分片上传和断点上传：

前端代码示例（使用Fetch API）

javascript 复制代码

const chunkSize = 1024 * 1024; // 每个分片大小为1MB
let file;
let chunks = [];

document.getElementById('fileInput').addEventListener('change', function(event) {
    file = event.target.files[0];
});

function uploadChunk(chunkData, totalChunks, chunkIndex) {
    const formData = new FormData();
    formData.append('chunk', chunkData);
    formData.append('totalChunks', totalChunks);
    formData.append('chunkIndex', chunkIndex);

    fetch('https://api.example.com/uploadChunk', {
        method: 'POST',
        body: formData
    })
    .then(response => {
        if (!response.ok) {
            throw new Error('Network response was not ok');
        }
        return response.json();
    })
    .then(data => {
        console.log('Chunk uploaded successfully:', data);
        if (chunkIndex < chunks.length - 1) {
            uploadNextChunk(chunkIndex + 1);
        } else {
            console.log('File upload complete!');
        }
    })
    .catch(error => {
        console.error('There was a problem with the upload operation: ', error);
    });
}

function uploadNextChunk(chunkIndex) {
    uploadChunk(chunks[chunkIndex], chunks.length, chunkIndex);
}

function uploadFile() {
    if (!file) {
        console.error('Please select a file.');
        return;
    }

    let fileSize = file.size;
    let numberOfChunks = Math.ceil(fileSize / chunkSize);

    for (let i = 0; i < numberOfChunks; i++) {
        let start = i * chunkSize;
        let end = Math.min(fileSize, start + chunkSize);
        let chunk = file.slice(start, end);
        chunks.push(chunk);
    }

    uploadNextChunk(0); // 开始上传第一个分片
}

在上述前端代码中，uploadFile()函数会将文件分片后逐个上传到后端，如果其中某个分片上传失败，可以通过保存当前上传进度信息，再次发起上传请求来实现断点续传。

后端处理示例（基于Node.js和Express）

javascript 复制代码

const express = require('express');
const multer = require('multer');
const fs = require('fs');

const app = express();
const upload = multer({ dest: 'uploads/' });

app.post('/uploadChunk', upload.single('chunk'), (req, res) => {
    const chunk = req.file;
    const totalChunks = parseInt(req.body.totalChunks);
    const chunkIndex = parseInt(req.body.chunkIndex);

    // 保存分片文件
    fs.rename(chunk.path, `uploads/chunk_${chunkIndex}`, err => {
        if (err) {
            console.error(err);
            res.status(500).json({ message: 'Error saving chunk' });
        } else {
            res.json({ message: 'Chunk uploaded successfully' });
        }
    });
});

app.listen(3000, () => {
    console.log('Server is running on http://localhost:3000');
});

以上是一个简单的示例代码，用于演示在前端实现大文件的分片上传和断点上传功能。在实际项目中，需要根据具体需求和后端服务的不同进行适当调整和扩展。