| Interface | Description |
|---|---|
| Extensible<T> |
An interface for extensible classes.
|
| Class | Description |
|---|---|
| CellExtension |
A base class for extensions of cells in a spreadsheet that uses delegation
to provide cell data.
|
| Extension |
An interface for extensions to the CleanSheets application.
|
| ExtensionManager |
The class that manages extensions to the CleanSheets application.
|
| ExtensionManager.Loader |
The class loader used to load extensions.
|
| SpreadsheetExtension |
A base class for extensions of spreadsheets that uses delegation
to provide cell data.
|
Provides an extension mechanism for the application. The basic capabilities
of the CleanSheets application is extended by means of inheritance by
delegation. Two abstract base-classes (CellExtension and
SpreadsheetExtension) are provided that implement the
Cell and Spreadsheet interface respectively.
There, calls to methods in each interface are delegated to an instance of
CellImpl or SpreadsheetImpl. Both of these interfaces
extend the Extensible interface, whereby extensions can be accessed
by the getExtension(String) method.
In order to improve on the existing functionality, extensions may provide sub-classes of these two base-classes. Sub-classes are required to be serializable.
An Extension has three parts. Apart from the two listed above (of
which at least one should be provided), all extensions should provide a
UIExtension that acts as a facade for retrieving
extension-specific user interface components, to be integrated into the
application's user interface.
Extensions are loaded dynamically on start-up using the class names listed in
the extension properties files. Known extensions are loaded if already in the
class path. If any of those conditions is not met, extensions should be listed
in a file named extensions.xml in the directory from which the
application is executed. The file is a standard XML properties files, where
entries for extensions should have the class name of the extension as key,
and an optional class path specification as value. The class path can be given
as a URL or local filename referring to a JAR-file or a directory where the
extension class can be found. (See example below.)
<?xml version="1.0" encoding="UTF-8"?> <!DOCTYPE properties SYSTEM "http://java.sun.com/dtd/properties.dtd"> <properties> <entry key="csheets.ext.assertion.AssertionExtension"/> <entry key="csheets.ext.test.TestExtension">test.jar</entry> </properties>
csheets.ui.ext