Netui:form and netui:hidden/textbox/... required datasource

Question

Hi all,
1) Question
Can I set the value of the netui:hidden tag different from the field to
which it will post it's content?
because datasource both defines the data to get and set to, which makes
dynamicaly generating a form in a loop seem impossible.
2) Problem illustration
In a jsp of a pageflow in Portal 8.1 I am iterating through an n-size list.
How do I dynamically generate a form for each item in the list?
How does the datasource attribute actually works?
<%
List bookList = (List) session.getAttribute("bookList");
<table>
<%
Iterator it = bookList.iterator();
while (it.hasNext()) {
BookTO book = (BookTO) it.next();
pageContext.setAttribute("book", book);
%>
<tr>
<td>
<netui:label value="<%=book.getName()%>"/>
</td>
<netui:form action="viewBook">
<netui:hidden dataSource="{book.isbnPK}"/>
<%-- Generates a NETUI ERROR when
clicking on the button (not before) --%>
<td>
<netui:button value="View"/>
</td>
</netui:form>
</tr>
<%
%>
</table>
It places the isbnPK in the form without any problems,
but when submitting the form it generates this error:
NETUI ERROR: Unable to update expression "{book.isbnPK}" with the
value [1-56592-403-7]. The typical cause is that the object represented by
the
expression is not available or is the wrong type for updating.
The BookForm and the BookTO have these methods though:
public String getIsbnPK() {
return isbnPK;
public void setIsbnPK(String isbnPK) {
this.isbnPK = isbnPK;
And in the pageflow:
protected Forward viewBook(BookForm form) {
Thank you for any and all help,
Geoffrey

Answer 1

Figured it out.
One of the other portlets on the page had a refreshAction property set to call the begin() method for that portlets controller when the page is refreshed. It was trying to accept the multipart form data sent from the other portlet and obviously wasn't set to accept multipart data. Removing the refreshAction property fixed the problem.