java上传大文件到云服务器

上传大文件到云服务器可以采用分块上传的方式，其中Java有很多第三方库可以实现这个功能，例如Apache Commons FileUpload、OkHttp、Retrofit等等。以下是一个基本的分块上传实现的示例代码：

import okhttp3.*;

import java.io.File;
import java.io.IOException;

public class ChunkedUpload {
    private static final String SERVER_URL = "http://your_server_url/upload";

    public static void main(String[] args) throws IOException {
        OkHttpClient client = new OkHttpClient();

        // 1. 打开文件
        File file = new File("path/to/your/file");
        long fileSize = file.length();

        // 2. 计算分块数目
        int chunkSize = 1024 * 1024; // 每个分块的大小为1MB
        int chunkNum = (int) Math.ceil((double) fileSize / chunkSize);

        // 3. 开始分块上传
        for (int i = 0; i < chunkNum; i++) {
            long offset = i * chunkSize;
            long currentChunkSize = Math.min(chunkSize, fileSize - offset);

            RequestBody requestBody = new MultipartBody.Builder()
                    .setType(MultipartBody.FORM)
                    .addFormDataPart("chunk", String.valueOf(i))
                    .addFormDataPart("chunks", String.valueOf(chunkNum))
                    .addFormDataPart("file", file.getName(),
                            RequestBody.create(MediaType.parse("application/octet-stream"),
                                    file, offset, currentChunkSize))
                    .build();

            Request request = new Request.Builder()
                    .url(SERVER_URL)
                    .post(requestBody)
                    .build();

            Response response = client.newCall(request).execute();

            if (!response.isSuccessful()) {
                throw new IOException("Unexpected response code: " + response);
            }
        }

        System.out.println("Upload completed!");
    }
}

注：以上代码仅供参考，实际生产环境中需要注意文件上传的安全性和可靠性。