Learning Java, 4th Edition

Properties and Customizers

Properties represent the “state” or “data” content of a bean. These features can be manipulated externally to configure the bean. For a bean that’s a GUI component, you might expect its properties to include its size, colors, and other features of its basic appearance. Properties are similar in concept to an object’s public variables. Like a variable, a property can be a primitive type (such as a number or Boolean), or it can be a complex object type (such as a String or a collection of spreadsheet data). Unlike variables, properties are always manipulated using methods to set and get the value; this enables a bean to take action whenever a property changes. By sending an event when a property changes, a bean can notify other interested beans of the change (which we will discuss later in this chapter).

Let’s pull a couple of beans into NetBeans and take a look at their properties. Click on a button (this will be a JButton) from the Swing Controls group of the palette, and then click in the workspace. When the JButton was first loaded by NetBeans, it was inspected to discover its properties. When we select an instance of the button, NetBeans displays these properties in the Properties pane and allows us to modify them.

The button has about eight basic properties, followed by a few additional groupings. The list called Other Properties adds more detail. There is also a Layout properties section (these are in actuality not properties of the JButton, but are ...