HTMLB fileUpload

I am using the hbj:fileUpload tag in a JSP page.

I would like to initialize the input field of the tag, but could not find any documentation.

I tried following, but it seems not to work:

<hbj:fileUpload id="fileUpload" size ="50" >

<%fileUpload.setFile( uploadBean.getSource());%>

</hbj:fileUpload>

Method getSource() returns a valid IFileParam object.