// PSEUDO-CODE:
// source.jsp
Download your file
<a href="file.jsp?xyz">MyDocument.doc</a>


// file.jsp
<%@page content-type="pplicaton/somethig-binary-xyz"%>
byte[] data = getBinaryFromSomeWhere();

int start = 0;
int end = data.length < 1024 ? data.length : 1024;
int written = 0;
while( written < data.length ) {
    out.write( data, start, end );
    writtern += end;
    start = end;
    end += written + data.length < 1024 ? data.length : 1024;
}

%>

<%@page content-type="applicaton/octet-stream"%><%
byte[] data = getBinaryFromSomeWhere(request.getParameter("xyz"));
request.setHeader("Content-length", Integer.toString(data.length));
out.write( data, start, end );
out.flush();
%>