It’s not all gold and sunshine; JavaFX layout

After my previous post, praising the properties and binding mechanism, I’d also like to voice an opinion on something on which I think the JavaFX team has dropped the ball.

In the previous post about Agenda control I explained that there were two ways I updated the nodes in Agenda; either I setup binding in the constructor, or I listen to relevant properties and call a relayout() method, setting the appropriate values there. Especially the binding is a powerful feature. No software engineer can deny that the sniplets below don’t have a certain beauty to them.

Adding a rectangle that serves as a dragger at the bottom of an appointment:


durationDragger.xProperty().bind(widthProperty().multiply(0.25)); // 25% offset from the left border
durationDragger.widthProperty().bind(widthProperty().multiply(0.5)); // 50% of the width of the appointment
durationDragger.yProperty().bind(heightProperty().subtract(5)); // 5 pixels from the bottom border
durationDragger.setHeight(3); // 3 pixels high

Making sure the day head and day body line up:


header.getChildren().add(dayHeader);
week.getChrildren().add(dayBody);
dayHeader.xProperty().bind( dayBody.xProperty());
dayHeader.widthProperty().bind( dayBody.widthProperty());

What is important here is that the x,y,w,h values are set directly on the children. The container does not do any layout, it simply draws its childeren where they say they want to be. This is called an ‘absolute’ layout. All other layouts (VBox, HBox, BorderPane, …) do not want you to set the x,y,w,h of the children, their added value is that they’ll calculate and set them for you. Continue reading “It’s not all gold and sunshine; JavaFX layout”

Writing Google Calendar in JavaFX

After getting my feet wet writing the ListPicker and CalendarPicker control in JavaFX for the JFXtras project, I felt it was time to put my aim at something bigger; I always wanted to write a control that does a “Google Calendar”. Even though such a control on the surface seems simple, there are many things that make it a real challenge and fun for a software engineer to create. For example the beauty of how overlapping appointments are rendered. So after a few days where the spare time went into drawings and scribbles on paper, fleshing out how things should be set it up, the coding started. There were a few things I would like to do different from Google’s version.

  1. When I plan an appointment, I always forget to look at the whole day events, and often get conflicts because of that. So I wanted a whole day event to have a presence during the whole day.
  2. Google only allows for appointments that span a certain amount time. Tasks (which basically only have a single date & time) are not supported. Google has a task feature, but it is not mature enough IMHO in terms of reminders and visibility.

So before diving into how the control is set up, first a quick peek at the state of affairs when writing this blog (tasks are not implemented yet):

Continue reading “Writing Google Calendar in JavaFX”

Stand alone business model with Activiti, Eclipselink and unit tests on PostgreSQL

Somewhere around 2007 – 2008 I was setting up a new project which had a business model (BM) as the central component. The business model I envisioned had a three layered structure: an AbstractBean handling all the Java bean plumbing, a from-the-database-reverse-engineered class with the properties (setters and getters), and finally a class containing the custom code on top. I wanted to settle on a standard (JPA) and tried using Hibernate at first, but it could not support this layered structure back then, so I ended up using Eclipselink (and with great satisfaction ever since, I must add).

I also have never been a fan of pure application servers (EJBs), so this BM is compiled into a single jar (already postprocessed by Eclipselink), and simply included in all kinds of applications; a client-server Swing application, a REST interface to support an Android app, several im- and exporters for EDIFACT, emails, XML, and of course a nice in-house webapp. Not having an additional single point of failure (besides the database) is very pleasing and keeps the overall architecture much more simple. Continue reading “Stand alone business model with Activiti, Eclipselink and unit tests on PostgreSQL”