java获取文件上传进度

To get the progress of a file upload in Java, you can use a `ProgressListener` that updates the progress of the upload as it is happening. Here's an example of how you might implement a `ProgressListener` using the Apache Commons FileUpload library:

import org.apache.commons.fileupload.ProgressListener;

public class UploadProgressListener implements ProgressListener {

    private long megaBytes = -1;

    @Override
    public void update(long pBytesRead, long pContentLength, int pItems) {
        long mBytes = pBytesRead / 1000000;
        if (megaBytes == mBytes) {
            return;
        }
        megaBytes = mBytes;
        System.out.println("We are currently reading item " + pItems);
        if (pContentLength == -1) {
            System.out.println("So far, " + pBytesRead + " bytes have been read.");
        } else {
            System.out.println("So far, " + pBytesRead + " of " + pContentLength
                    + " bytes have been read.");
        }
    }
}

To use the `ProgressListener`, you will need to create an instance of it and pass it to the `FileUpload` object when you are parsing the request. Here's an example of how you might do this:

import org.apache.commons.fileupload.FileItem;
import org.apache.commons.fileupload.FileUpload;
import org.apache.commons.fileupload.FileUploadBase;
import org.apache.commons.fileupload.disk.DiskFileItemFactory;
import org.apache.commons.fileupload.servlet.ServletFileUpload;

import javax.servlet.http.HttpServletRequest;
import java.util.List;

public class FileUploader {

    public void handleFileUpload(HttpServletRequest request) throws Exception {
        // Create a factory for disk-based file items
        DiskFileItemFactory factory = new DiskFileItemFactory();

        // Create a new file upload handler
        ServletFileUpload upload = new ServletFileUpload(factory);

        // Set progress listener
        upload.setProgressListener(new UploadProgressListener());

        // Parse the request
        List<FileItem> items = upload.parseRequest(request);

        // Process the uploaded items
        for (FileItem item : items) {
            if (!item.isFormField()) {
                // It's a file upload
                String fileName = item.getName();
                // Process the uploaded file
            } else {
                // It's a regular form field
                String fieldName = item.getFieldName();
                String fieldValue = item.getString();
                // Process the form field
            }
        }
    }
}

I hope this helps! Let me know if you have any questions.