获取文件上载对象的输入流

import oracle.jbo.domain.BlobDomain;
import oracle.cabo.ui.data.DataObject;
import java.io.InputStream;
在CO.java中，
DataObject fileUploadData =
(DataObject)pageContext.getNamedDataObject();
String fileName =
(String)fileUploadData.selectValue(null, "UPLOAD_FILE_NAME");

//BlobDomain uploadedByteStream =
(BlobDomain)fileUploadData.selectValue(null, fileName);//这句有问题,总是取出空值，改为下面的语句：
BlobDomain uploadedByteStream = (BlobDomain)pageContext.getParameterObject(fileName);

InputStream inputStream = uploadedByteStream.getInputStream();