Java Accessibility: The Bridge to Native Code

JAVA ACCESSIBILITY

Java Accessibility Bridge to Native Code

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The Java Accessibility Bridge to Native Code

In order for existing assistive technologies available on host systems (e.g. Microsoft Windows, Macintosh, OS/2) to provide access to Java applications, they need some way to communicate with the Java Accessibility support in those Java applications. The Java Accessibility Bridge supports that communication. This bridge is a class which contains "native methods." Part of the code for the class is actually supplied by a DLL on the host system - Solaris, OS/2, Microsoft Windows, Macintosh, etc. The assistive technology running on the host (e.g., a Macintosh screen reader) communicates with the Macintosh native DLL portion of the bridge class, which in turn communicates with the Java Virtual Machine, and from there to the Java Accessibility utility support and the Java Accessibility API on the individual user interface objects of the Java application it is providing access to.

A diagram of how all of these components work together is shown below.

Figure: Diagram of How the Java Accessibility Bridge Works

For example, in order for a screen reader for Microsoft Windows to provide access to Java applications running on that system, that screen reader would make calls to the Java Accessibility Bridge for Microsoft Windows. If/when a the user launched a Java application, the bridge would inform the screen reader of this fact. Then the screen reader would query the bridge about the Java application and the bridge would in turn forward those queries on to the Java Accessibility Utilities that were loaded into the Java Virtual Machine, and in many cases on to the individual user interface object that implemented the Java Accessibility API. When those answers came back to the bridge, the bridge would forward them on to the screen reader for Microsoft Windows, which would then use the answers to tell the user what was going on in the Java application.

To submit comments or suggestions about Java Accessibility, please send mail to access@sun.com.