best bet is to factor that blob into its own entity and declare the class lazy.
Code:
public class MetaData {
int id;
FileData fileContents;
...
}
public class FileData {
int id;
MetaData metaData
byte[] contents;
...
}
<class name="MetaData">
...
<one-to-one name="FileContents" class="FileData" cascade="all-delete-orphan" />
...
</class>
<class name="FileData" lazy="true">
...
<one-to-one name="MetaData" class="MetaData" constrained="true" />
...
</class>
the above mapping works when you have a separate table for the file contents with a PK->PK,FK link between the two tables.
-devon