plz check these stuffs, hopefully they work out. (not sequential)

1. "items" must be defined as a variable of <f:dataTable e.g.:
<t:dataTable value="#{aBean.collectionItems}" var="items" ...

2. Define getCollectionItems, which returns a Collection, in bean of class A.

3. Class A should be Serializable. e.g. public class A implements Serializable {...};

4. Class A must be defined in your faces-config.xml

Actually, jsf  errors and exceptions are really crap :)) But, JSF is so useful and I believe that it will capture the interface layer market or at least it is influenced dramatically, by the way.

Obviously, you can buy whatever you want and need through the Amazon.com. probably you can find free e-book about JSF in the following listed web sites, but I'm not sure, cos I didnt try to find it before.

www.free-itebooks.com
www.freeebookdownload.net
www.ebookee.com

Also, I've found http://horstmann.com/corejsf/jsf-tags.html pretty useful. It describes basic JSF tags. Apache is good, as well. and if u can find the following book can really helpful, especially in advance usage of JSF, configiration stuff like that:
Mann, K.D. (2005), "JSF in Action", Manning, USA