如何在Vaadin中使用ByteArrayOutputStream上传图像？

Question

我希望将上传的图像作为字节数组接收（以便可以将其插入到sql数据库中）。 我还想将上传的图像显示为预览。

我已经尝试了以下代码，但我没有收到完整图像的字节。 （如果我打印字节数组，它只打印几个字符）

final Embedded preview = new Embedded("Uploaded Image");
preview.setVisible(false);

final Upload upload = new Upload();
upload.setCaption("Image");

// Create upload stream
final ByteArrayOutputStream baos = new ByteArrayOutputStream(); // Stream to write to

upload.setReceiver(new Upload.Receiver() {
    @Override
    public OutputStream receiveUpload(String filename, String mimeType) {

        return baos; // Return the output stream to write to
    }
});

upload.addSucceededListener(new Upload.SucceededListener() {
    @Override
    public void uploadSucceeded(Upload.SucceededEvent succeededEvent) {
        final byte[] bytes = baos.toByteArray();

        preview.setVisible(true);
        preview.setSource(new StreamResource(new StreamResource.StreamSource() {
            @Override
            public InputStream getStream() {
                return new ByteArrayInputStream(bytes);
            }
        }, ""));

    }
});

Answer 1

image.setSource(new StreamResource(new StreamResource.StreamSource() {
  @Override
  public InputStream getStream() {
    return new ByteArrayInputStream(baos.toByteArray());
  }
}, ""));

Answer 2

您可以尝试将带有一些日志的ProgressListener添加到Upload上，以查看发生了什么；您将获得读取字节数和总内容长度作为updateProgress方法的参数，以便查看是否所有内容都已发送。