Why tomcat act like it error?

I use tomcat 5.5.20 and I following the chapter8 of HFSJ book. In the "type attribute" topic (page 353-355)
This is my servlet code.

and "attribute code"

and the result.jsp code

The problem is: when I use the above result.jsp the container will produce the error page. But if I modify the .jsp file to

Then the .jsp page will work fine and show the result without error.

Even if I edit the servlet code from

TO

The page is also work fine, even though the "new Person();" is exactly wrong syntax for java (Person is abstract class) but it work.

I don't understand the tomcat behavior, that act not according to the book.

PS. I recompile the code every time I change it, so it is not the "version" relate problem.

Thank you
Tanakorn

Check your Tomcat error logs. It should provide you with more information about when the error happens.