Observations in Migrating from JavaFX
Script to JavaFX 2.0
Introduction
Having been available for a few years now, there is a decent
body of work written for JavaFX using the JavaFX Script language. With the general availability announcement of JavaFX 2.0 Beta, the natural question arises about
converting the legacy code over to the new JavaFX 2.0 platform. This article reflects
on some of the observations encountered while porting source code over from
JavaFX Script to the new JavaFX API paradigm.
The Application
The program chosen for migration is an implementation of the
Sudoku game and serves as a reference application for the book JavaFX – Developing Rich Internet
Applications. The design of the
program can be divided into two major components: (1) A user interface (ideally
suited for JavaFX design) and (2) the puzzle generator. For the context of this article, our primary
interest lies in the user interface. The
puzzle generator code was lifted from a sourceforge.net project and is written entirely
in Java. Regardless which version of the
UI we choose (JavaFX Script vs. JavaFX 2.0), no code changes were required for the puzzle generator code.
The original user interface for the JavaFX Sudoku application
was written exclusively in JavaFX Script, and as such is a suitable candidate to
convert over to the new JavaFX 2.0
model. However, a few notable points are worth
mentioning about this program. First
off, it was written in the JavaFX 1.1 timeframe, where certain capabilities of
the JavaFX framework were as of yet unavailable. Citing two examples, this program creates
many of its own UI controls from scratch because the built-in controls were yet
to be introduced. In addition, layout of
graphical nodes is done in a very manual manner, again because much of the
automatic layout capabilities were in flux at the time. It is worth considering that this
program was written at a time when most of us were just coming up to speed on
this technology. One would think that
having the opportunity to recreate this application anew, it would look a lot
different from the current version.
Comparing the Size of
the Source Code
An attempt was made to convert each of the original UI JavaFX
Script source files (suffixed with .fx) over to a Java counterpart. Due to language feature differences, there
are a small number of source files which only exist in one version or the
other. The table below summarizes the
size of each of the source files.
JavaFX Script source file
Number of Lines
Number of Character
JavaFX 2.0 Java source file
Number of Lines
Number of Characters
ArrowKey.java
6
72
Board.fx
221
6831
Board.java
205
6508
BoardNode.fx
446
16054
BoardNode.java
723
29356
ChooseNumberNode.fx
168
5267
ChooseNumberNode.java
302
10235
CloseButtonNode.fx
115
3408
CloseButton.java
99
2883
ParentWithKeyTraversal.java
111
3276
FunctionPtr.java
6
80
Globals.java
20
554
Grouping.fx
8
140
HowToPlayNode.fx
121
3632
HowToPlayNode.java
136
4849
IconButtonNode.fx
196
5748
IconButtonNode.java
183
5865
Main.fx
98
3466
Main.java
64
2118
SliderNode.fx
288
10349
SliderNode.java
350
13048
Space.fx
78
1696
Space.java
106
2095
SpaceNode.fx
227
6703
SpaceNode.java
220
6861
TraversalHelper.fx
111
3095
Total
2,077
79,127
2531
87,800
A few notes about this table are in order:
The number of lines in each file was determined
by running the Unix ‘wc –l’ command over each file.
The number of characters in each file was
determined by running the Unix ‘ls –l’ command over each file.
The examination of the code could certainly be
much more rigorous. No standard formatting was performed on these files. All comments however were deleted.
There was a certain expectation that the new Java version
would require more lines of code than the original JavaFX script version. As evidenced by a count of the total number
of lines, the Java version has about 22% more lines than its FX Script
counterpart.
Furthermore, there was an additional expectation
that the Java version would be more verbose in terms of the total number of
characters. In fact the preceding data shows that on average the Java source files contain fewer characters per line than the FX files. But that's not the whole story. Upon further examination, the FX Script source files had a disproportionate number of blank characters. Why? Because of the nature of how one develops JavaFX Script code. The object literal dominates FX Script code. Its not uncommon to see object literals indented halfway across the page, consuming lots of meaningless space characters.
RAM consumption
Not the most scientific analysis, memory usage for
the application was examined on a Windows Vista system by running the Windows
Task Manager and viewing how much memory was being consumed by the Sudoku
version in question. Roughly speaking, the
FX script version, after startup, had a RAM footprint of about 90MB and remained
pretty much the same size. The Java
version started out at about 55MB and maintained that size throughout its execution.
What About Binding?
Arguably, the most striking observation about the conversion
from JavaFX Script to JavaFX 2.0 concerned the need for data synchronization, or lack thereof. In JavaFX Script, the primary means to synchronize
data is via the bind expression (using the “bind” keyword), and perhaps to a
lesser extent it’s “on replace” cousin. The bind keyword does not exist in Java, so for JavaFX 2.0 a Data Binding API has been introduced as a replacement.
To give a feel for the difference between the two versions
of the Sudoku program, the table that follows indicates how many binds were
required for each source file. For
JavaFX Script files, this was ascertained by simply counting the number of
occurrences of the bind keyword. As can be seen, binding had been used
frequently in the JavaFX Script version (and does not take into consideration
an additional half dozen or so “on
replace” triggers). The JavaFX 2.0 program achieves the same functionality as the original JavaFX Script version,
yet the equivalent of binding was only needed twice throughout the Java version of the source code.
JavaFX Script source file
Number of Binds
JavaFX Next Java source file
Number of “Binds”
ArrowKey.java
0
Board.fx
1
Board.java
0
BoardNode.fx
7
BoardNode.java
0
ChooseNumberNode.fx
11
ChooseNumberNode.java
0
CloseButtonNode.fx
6
CloseButton.java
0
CustomNodeWithKeyTraversal.java
0
FunctionPtr.java
0
Globals.java
0
Grouping.fx
0
HowToPlayNode.fx
7
HowToPlayNode.java
0
IconButtonNode.fx
9
IconButtonNode.java
0
Main.fx
1
Main.java
0
Main_Mobile.fx
1
SliderNode.fx
6
SliderNode.java
1
Space.fx
0
Space.java
0
SpaceNode.fx
9
SpaceNode.java
1
TraversalHelper.fx
0
Total
58
2
Conclusions
As the JavaFX 2.0 technology is so new, and experience
with the platform is the same, it is possible and indeed probable that some of
the observations noted in the preceding article may not apply across other
attempts at migrating applications. That
being said, this first experience indicates that the migrated Java code will
likely be larger, though not extensively so, than the original Java FX Script
source. Furthermore, although very
important, it appears that the requirements for data synchronization via
binding, may be significantly less with the new platform.
