Hi Everyone,
my programming experience is from the era that Pascal still was a populair language and object oriented wasn't invented. So you can say that I'm completely illiterate to anything more advanced than an if ... then statement. I am currently trying to get a linux (tomcat-web) server running and up until now it all seemed to work. I've got the following configuration running (among a few other components):
Fedora 10
Apache HTTP 2.2
Tomcat 6
JRE 1.6
After that I started working through a book called "Beginning JSP, JSF and Tomcat Web Development". I managed to compile the java bean and the servlet that's in the first chapter. Now, here's the problem. During compilation of the servlet there was 1 warning.Here it is:
ShoppingServlet.java:20: warning: [unchecked] unchecked cast
found : java.lang.Object
required: java.util.Vector<ebookshop.Book>
Vector<Book> shoplist = (Vector<Book>)session.getAttribute("ebookshop.cart");
^
Maybe wrong allready, but I chose to ignore that one. After that I pulled up the application in my webbrowser and pushed the "add to cart" button of my first webapp it gave an error message in my browser:
HTTP Status 500 -
type Exception report
message
description The server encountered an internal error () that prevented it from fulfilling this request.
exception
java.lang.NullPointerException
ebookshop.ShoppingServlet.getBook(ShoppingServlet.java:87)
ebookshop.ShoppingServlet.doPost(ShoppingServlet.java:58)
javax.servlet.http.HttpServlet.service(HttpServlet.java:637)
javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
note The full stack trace of the root cause is available in the Apache Tomcat/6.0.18 logs.
Apache Tomcat/6.0.18
I've tried looking into the code to make some sense of this, but I'm really stuck here. Anyone who wants to offer some help would be more than welcome.
Regards,
Martijn