Java EE (Java Enterprise Edition) General Discussion

I got this error when trying the tiles framework. I did some search and but did not resolve. It suggest using different URI for the taglib. I did not have any problem when I run the complete tile example. It only happened when I used my test tile program. What am I doing wrong?
Summary of what I did for this simple test (if it helps to trace the problem)
1. create a simple layout (layout.jsp)
2. define definition in titles.xml
3. use the definition in the index.jsp


----------------------------errror---------------------------------------------------------------------------------
java.lang.ClassNotFoundException: org.apache.struts.taglib.tiles.UseAttributeTei
at java.net.URLClassLoader$1.run(URLClassLoader.java:200)
at java.security.AccessController.doPrivileged(Native Method)