Tiles Error

When i integrate tiles with struts its giving the following error

Error Page
The following java.lang.NullPointerException Occured

Exception occured in the following place

java.lang.NullPointerException
at org.apache.struts.taglib.tiles.InsertTag.processAttribute(InsertTag.java:689)
at org.apache.struts.taglib.tiles.InsertTag.createTagHandler(InsertTag.java:489)
at org.apache.struts.taglib.tiles.InsertTag.doStartTag(InsertTag.java:451)
at _jsp._cts_2d_web._jspService(cts-web.jsp:20)
at com.orionserver.http.OrionHttpJspPage.service(OrionHttpJspPage.java:57)
at oracle.jsp.runtimev2.JspPageTable.service(JspPageTable.java:347)
at oracle.jsp.runtimev2.JspServlet.internalService(JspServlet.java:509)
at oracle.jsp.runtimev2.JspServlet.service(JspServlet.java:413)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:853)
at com.evermind.server.http.ResourceFilterChain.doFilter(ResourceFilterChain.java:65)
at oracle.security.jazn.oc4j.JAZNFilter.doFilter(Unknown Source)
at com.evermind.server.http.ServletRequestDispatcher.invoke(ServletRequestDispatcher.java:649)
at com.evermind.server.http.ServletRequestDispatcher.forwardInternal(ServletRequestDispatcher.java:322)
at com.evermind.server.http.HttpRequestHandler.processRequest(HttpRequestHandler.java:790)
at com.evermind.server.http.HttpRequestHandler.run(HttpRequestHandler.java:270)
at com.evermind.server.http.HttpRequestHandler.run(HttpRequestHandler.java:112)
at com.evermind.util.ReleasableResourcePooledExecutor$MyWorker.run(ReleasableResourcePooledExecutor.java:192)
at java.lang.Thread.run(Thread.java:534)

Help me please..............

you have a tiles definition defined in your xml that extends a master tile that contains less attributes than what you provided in your master definition. basically, your master tile jsp has a tiles:insert tag that doesn't have a value provided for as specified by the attribute(either in the tiles-def.xml or in the specific tiles jsp). make sure a value is provided for each tiles:insert that you defined.

Thanks Alan...

To use a tiles definition, we need to create a definition in tiles-defs.xml and can start using the definition in any jsp with <put> tag right?

If i am wrong will you tell me how to do it?

http://www.theserverside.com/articles/article.tss?l=Tiles101
follow the tiles 101 section

http://www.javaworld.com/javaworld/jw-01-2002/jw-0104-tilestrut.html
i highly recommend following solution #6 and #7 to use tiles declaratively.

I had exactly the same error. After hours, I found a trick to do before searching paths diplayed above.
Clean the Work dir of tomcat, simple, isn't it ! Looks like this incredibly stupid thing keeps some data even after full server start. it could simply prevent you from having a good display even after correcting the tiles issues.