I shouldn’t care about this because I don’t use JavaFX. But it bugs me so I’ll rant a bit.
A while ago (probably around version 1.2) the language caught my eye. I especially liked its literal declarative syntax for creating tree structures and data binding. I thought I heard that Oracle was discontinuing JavaFX but version 2.0 is in beta. I now realize that it is only JavaFX Script that is canned — JavaFX is alive and well. (JavaFX Script lives on in visage.) The features of JavaFX are available as APIs that can be used from Java or other languages on the JVM. This is a good architecture.
Writing procedural code to construct a scene graph looks as ugly and cumbersome as JavaFX Script was elegant. To “fix” this problem FXML was invented. FXML is a XML dialect for declaring a scene graph.
From what I have read there are two main motivations for using XML:
- Familiarity — from the getting started with FXML page: “One of the advantages of FXML is that it is based on XML and is therefore familiar to most developers”
- No need to compile (presumably changes to FXML are made on the fly without having to restart the app). This is fair but doesn’t imply that XML is a good answer.
The familiarity argument is false. It confuses syntax with semantics. Yes many developers are familiar with the syntax of XML but just because someone knows XML Schema doesn’t mean they will have any understanding of XSLT. One must still learn the semantics of FXML and that’s the hard part.
Here is what I think is bad about FXML:
- XML is just not a convenient language for source code. It is verbose and cumbersome. It has lots of little things that get in the way such as entity references. New programming languages including declarative ones should not be XML.
- Use of character case in element names to distinguish between instances and properties is ugly.
- Properties can be represented by either XML attributes or XML elements. This is practical but confusing and stems from using the wrong tool for the job (XML).
- Type coercion.
And a few things I liked:
- Use of XML processing instructions.
- Built-in support for string translation. But it doesn’t go far enough. It should eliminate the need for maintaining resource property files and support format substitutions.
- Concept of static properties.