java断点续传前后端交互实现代码

Java断点续传需要前后端交互实现，以下是一个简单的示例代码：

前端代码（使用jQuery）：

$(function() {
  var fileInput = $('#fileInput');
  var fileSize = fileInput[0].files[0].size;
  var startByte = 0;

  $('#uploadButton').click(function() {
    var formData = new FormData();
    formData.append('file', fileInput[0].files[0]);
    formData.append('startByte', startByte);
    $.ajax({
      url: '/upload',
      type: 'POST',
      data: formData,
      processData: false,
      contentType: false,
      xhr: function() {
        var xhr = $.ajaxSettings.xhr();
        xhr.upload.onprogress = function(e) {
          if (e.lengthComputable) {
            var percent = Math.round((e.loaded + startByte) / fileSize * 100);
            $('#progressBar').css('width', percent + '%');
          }
        };
        return xhr;
      },
      success: function(response) {
        if (response.status === 'success') {
          startByte = response.startByte;
          if (startByte === fileSize) {
            alert('上传完成');
          }
        } else {
          alert('上传失败');
        }
      },
      error: function() {
        alert('上传失败');
      }
    });
  });
});

后端代码（使用Spring Boot）：

@RestController
public class UploadController {
  private static final String UPLOAD_DIR = "/path/to/upload/dir";
  private static final int BUFFER_SIZE = 1024 * 1024;

  @PostMapping("/upload")
  public Map<String, Object> upload(@RequestParam("file") MultipartFile file,
                                     @RequestParam("startByte") long startByte) throws IOException {
    File uploadDir = new File(UPLOAD_DIR);
    if (!uploadDir.exists()) {
      uploadDir.mkdirs();
    }

    File uploadFile = new File(uploadDir, file.getOriginalFilename());
    RandomAccessFile raf = new RandomAccessFile(uploadFile, "rw");
    raf.seek(startByte);

    InputStream in = file.getInputStream();
    byte[] buffer = new byte[BUFFER_SIZE];
    int len = 0;
    long totalBytesRead = startByte;
    while ((len = in.read(buffer)) != -1) {
      raf.write(buffer, 0, len);
      totalBytesRead += len;
    }

    raf.close();
    in.close();

    Map<String, Object> response = new HashMap<>();
    response.put("status", "success");
    response.put("startByte", totalBytesRead);
    return response;
  }
}

以上代码仅供参考，实际使用时需要根据具体需求进行修改。