Problems with awt.Toolkit on Tomcat

Question

Hello! I'm trying to get the Default Toolkit (java.awt.Toolkit.getDefaultToolkit() ) to determine the scrren size of the client, and Tomcat keeps throwing an Exception - now it's the website's Tomcat and the one on my localhost - there it worked.. Is there another way to determine the client's screen size in JSP (not JavaScript!)?? Thanx!

Answer 1

first, the previous poster was right - learn how these protocols are interacting before you try something like you want to do - and they're right, you can't use the AWT toolkit to find out ANYTHING about the client.
HTTP is stateless. so it's like this:
browser request -> your code on server, jsp completely exeutes, generates html -> html PLAIN old html goes to the browser. in that order. no exceptions. ergo, all your code has executed once the browser starts getting data (buffers on the server not withstanding).
As to why you're getting the exception, the server you are trying to run it on is most likely running in a mode called "headless", that is, there is no windowing api available to the JVM, so any awt calls will fail anyway. It works on your box because you are probably running a full windowing os, such as windows or Linux with gnome or kde. it just happens to return the correct screen size because that's the screen size of your screen, not the screen of the browser that it's outputting to. (try running your code locally and making your browser window small, you'll be dismayed that the rendered HTML is not the "right" size - because the screen size call was based on your resolution, NOT the size of the requesting browser window.
if the last 2 sentences don't make sense, re-read them until they do.
best of luck, sorry you're learing these frustrating lessons this way.