{"id":2218,"date":"2010-02-08T10:44:56","date_gmt":"2010-02-08T09:44:56","guid":{"rendered":"http:\/\/www.walkingrandomly.com\/?p=2218"},"modified":"2010-02-08T10:44:56","modified_gmt":"2010-02-08T09:44:56","slug":"fun-with-javafx-on-ubuntu-linux","status":"publish","type":"post","link":"https:\/\/walkingrandomly.com\/?p=2218","title":{"rendered":"Fun with JavaFX on Ubuntu Linux"},"content":{"rendered":"

A friend of mine<\/a> got me interested in JavaFX<\/a> recently and my interest grew when I discovered that it had some nice charting functionality<\/a>.\u00a0 Dean Iverson has written some great tutorials on the subject over at his blog<\/a> and includes a link to a demo showing some of the different plot types that are available.<\/p>\n

The demo is called ChartDemo and can be found here<\/p>\n

http:\/\/pleasingsoftware.blogspot.com\/2009\/06\/this-is-test.html<\/a><\/p>\n

In an ideal world you simply have to click on the demo’s screenshot for it to download and launch but that wasn’t what happened for me.\u00a0 What happened when I clicked on it was nothing.\u00a0 No error messages…just nothing.\u00a0 It’s difficult to google ‘nothing happened’ and get something useful so I downloaded the demo (which had the filename ChartDemo.jnlp) and tried to launch it from the command line using<\/p>\n

javaws ChartDemo.jnlp<\/pre>\n
This gave me the error message<\/p>\n
netx: Unexpected net.sourceforge.jnlp.ParseException: Invalid XML document syntax. at\r\nnet.sourceforge.jnlp.Parser.getRootNode(Parser.java:1200)<\/pre>\n
What follows is the story of how I eventually got this demo to work in the hope that it will help someone out there.<\/p>\n
So, first things first, what are some of the relevant system specs I am using?\u00a0 Well, I am running 32bit Ubuntu Linux 9.10 (Karmic Koala) and<\/p>\n
java -version<\/pre>\n
gives<\/p>\n
java version \"1.6.0_0\"\r\nOpenJDK Runtime Environment (IcedTea6 1.6.1) (6b16-1.6.1-3ubuntu1)\r\nOpenJDK Server VM (build 14.0-b16, mixed mode)<\/pre>\n
Now, when I googled the error message I discovered that Linux (more specifically, I guess, the OpenJDK<\/a>) is much more sensitive to xml errors than Windows\/Mac OS X (.jnlp files are written in xml).\u00a0 Take double quotes for example; according to the W3C XML recommendations<\/a> you should not use \\” inside an xml attribute but should use “&quot;” instead.\u00a0 Some java implementations don’t seem to care but, at the time of writing at least, OpenJDK definitely does.\u00a0 Follow this link <\/a>to see the original discussion thread where I learned this.<\/p>\n
The practical upshot of this extra level of strictness is that .jnlp files that work just fine on Windows and Mac OS X won’t work on Linux and I guessed that was what as happening here.\u00a0 Sadly there were no examples of \\” in ChartDemo.jnlp for me to change to “&quot;” so there must be something else ‘wrong’ with it; but what?<\/p>\n
I decided to try the ‘stare at it until you figure it out’ approach to debugging and left the laptop on the side of the sofa while watching a movie on TV.\u00a0\u00a0 About halfway through the movie, inspiration struck and I changed the line<\/p>\n
<update check=\"background\"><\/pre>\n
to<\/p>\n
<update check=\"background\"\/><\/pre>\n
which got things past the xml parsing stage.  Sadly, I then hit another problem.  Rather than a working ChartDemo, my efforts were rewarded with nothing more than just a blank window and a load of java errors in the terminal.  When I say ‘a load’ I mean HUNDREDS and none of them looked particularly illuminating.  I was starting to remember why I had avoided Java in the past but was not about to give up so easily.<\/p>\n
Let’s take stock:<\/p>\n