java 分片上传

Java 分片上传实现

1. 流程概述

分片上传是指将一个大文件切分成多个小的片段进行上传，然后在服务器端将这些片段合并成完整的文件。下面是实现分片上传的整个流程：

2. 代码实现

客户端代码

import java.io.*;
import java.net.HttpURLConnection;
import java.net.URL;

public class Client {
    public static void main(String[] args) {
        // 1. 将文件进行分片，生成多个小文件
        File file = new File("path/to/largeFile.mp4");
        int chunkSize = 1024 * 1024; // 每个分片的大小，这里设定为 1MB
        int totalChunks = (int) Math.ceil((double) file.length() / chunkSize);

        try (RandomAccessFile raf = new RandomAccessFile(file, "r")) {
            byte[] buffer = new byte[chunkSize];
            for (int i = 0; i < totalChunks; i++) {
                int bytesRead = raf.read(buffer);
                if (bytesRead == -1) {
                    break;
                }
                String chunkName = "chunk-" + (i + 1);
                // 2. 客户端逐个上传分片文件到服务器
                uploadChunk(chunkName, buffer, bytesRead);
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    public static void uploadChunk(String chunkName, byte[] data, int bytesRead) {
        String endpoint = " // 上传接口的URL
        try {
            URL url = new URL(endpoint);
            HttpURLConnection connection = (HttpURLConnection) url.openConnection();
            connection.setRequestMethod("POST");
            connection.setDoOutput(true);
            connection.setRequestProperty("Content-Type", "application/octet-stream");

            // 设置请求头，标识当前分片的信息
            connection.setRequestProperty("Chunk-Name", chunkName);
            connection.setRequestProperty("Content-Length", String.valueOf(bytesRead));

            // 通过输出流将分片数据写入请求体
            OutputStream outputStream = connection.getOutputStream();
            outputStream.write(data, 0, bytesRead);
            outputStream.flush();
            outputStream.close();

            int responseCode = connection.getResponseCode();
            if (responseCode == HttpURLConnection.HTTP_OK) {
                // 上传分片成功
                System.out.println("Chunk " + chunkName + " uploaded successfully.");
            } else {
                // 上传分片失败
                System.out.println("Failed to upload chunk " + chunkName);
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

以上代码实现了客户端的分片上传功能。首先，我们通过 RandomAccessFile 将大文件切分成多个小文件，每个小文件的大小由 chunkSize 决定。然后，逐个调用 uploadChunk 方法将分片文件上传到服务器。

服务器端代码

服务器端需要接收并保存分片文件，并在所有分片文件上传完毕后进行合并。下面是服务器端的代码示例：

import java.io.*;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.StandardOpenOption;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class Server extends HttpServlet {
    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        String chunkName = request.getHeader("Chunk-Name");
        int contentLength = Integer.parseInt(request.getHeader("Content-Length"));

        // 3. 服务器接收并保存分片文件
        saveChunk(chunkName, request.getInputStream(), contentLength);

        response.setStatus(HttpServletResponse.SC_OK);
        response.getWriter().flush();
    }

    public static void saveChunk(String chunkName, InputStream inputStream, int contentLength) throws IOException {
        File saveDirectory = new File("path/to/saveDirectory");
        if (!saveDirectory.exists()) {
            saveDirectory.mkdirs();
        }

        File chunkFile = new File(saveDirectory, chunkName);
        try (OutputStream outputStream = new FileOutputStream(chunkFile, true)) {
            byte[] buffer = new byte[4096];
            int bytesRead;
            while ((bytesRead = inputStream.read(buffer)) != -1) {
                outputStream.write(buffer, 0, bytesRead);
            }
        }

        // 4. 服务器合并分片文件
        mergeChunks(saveDirectory);
    }

    public static void mergeChunks(File saveDirectory) throws IOException {
        File[] chunks = saveDirectory.listFiles((dir