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InfoQ Homepage News JSR 295 Beans Binding Hits 1.0

JSR 295 Beans Binding Hits 1.0

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Shannon Hickey of Sun recently announced 1.0 of the Beans Binding Framework. This is the reference implementation of JSR 295 that seeks to:

...define an API that greatly simplifies connecting a pair of Java Beans properties to keep them in sync. The connection will be configurable: type conversion and validation operations may be applied before updating a property.

Shannon states that work on the JSR will still continue however and may result in API changes. Version 1.0 does however represent a major re-architecture of the Beans Binding API with the following highlights:

  • The concept of a property has been factored out into an abstract Property class, with two concrete implementations of interest: BeanProperty and ELProperty.
  • Binding is now an abstract class representing a binding between two Property instances (typically associated with two objects).
  • Binding with automatic syncing is implemented by a new concrete AutoBinding subclass.
  • Bindings to complex Swing components (such as JTable, JList and JComboBox) are now handled by custom Binding subclasses.
  • The synthetic Swing properties that offer multiple possible behaviors are now exposed via multiple versions of the property. For example: "text", "text_ON_FOCUS_LOST" and "text_ON_ACTION_OR_FOCUS_LOST" for JTextField; "selectedElement" and "selectedElement_IGNORE_ADJUSTING" for JList and JTable.
  • Everything has been repackaged into org.jdesktop packages.

Basic API for the framework is as follows:

// Bind Duke's first name to the text property of a Swing JTextField
BeanProperty textP = BeanProperty.create("text");
Binding binding =
Bindings.createAutoBinding(READ_WRITE, duke, firstP, textfield, textP);

// Bind Duke's mother's first name to the text property of a Swing JTextField,
// specifying that the JTextField's text property only reports change
// (thereby updating the source of the READ_WRITE binding) on focus lost
BeanProperty textP = BeanProperty.create("text_ON_FOCUS_LOST");
Binding binding =
Bindings.createAutoBinding(READ_WRITE, duke, motherFirstP, textfield, textP);

Beans Binding arrives in a Swing space that has used projects such as JGoodies Binding in the past. There is also the JFace Data Binding from the Eclipse Foundation. It provides core implementations for SWT, JFace and JavaBeans. However, the framework has been written with future expansion for API's like Swing and EMF.

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