Data Binding Concepts

Data bindings are simply links between a UI component and some data. The data binding implements everything that is needed to retrieve the data from a data source and update the UI component, plus all that is needed to store any input made in the UI component by the user. The data bindings work in an orchestrated way so that what is displayed to the user is consistent with what is in the datastore.

Data Binding In Depth

Carousel applications use the Model-View-Controller (MVC) pattern to separate the key concerns in building an application. A key principal of this separation is that the model can be implemented without overdue concern for the presentation layer or user interface. Keeping the model simple makes it easy to implement business logic.
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The separation of the model also means that the business logic need have little concern for the modalities or peculiarities of the user interface or the user interaction within the application.

Of course the model cannot be completely divorced from the user interface as occasionally interaction is required, say for instance if the model requires special input or needs to signal an error. Carousel achieves the separation of concerns espoused by the MVC architecture by implementing a loose coupling between the data model and the user interface.

On the data or model side of the architecture Carousel provides a rich data model that can be addressed via XML and XPath like references. This model can be composed of a wide variety of data and the data can be used in a variety of ways depending on the needs of the user interface and application.

Typically the data model will consist of data from a number of data sources such as static data defined in flat files, tables mapped in from a database, server side data obtained via service calls and configuration information.

Carousel also saves its own data to the model, for example saving the component state data to the xui_state node so that things like list selections indices can be accessed via the mode or used for master details linking.

Your application may also save data to the model as it needs. The model grows with your application and its content is highly configurable. For example each node within the model can have multiple child nodes and each node can be a rich type, not just the basic types built into Java. Tables themselves are good examples of these composite objects, consisting of multiple rows and with rows consisting of multiple fields.

The diagram below shows how various data sources might be mapped into the hierarchy and how an individual object can be a composite of other objects. The diagram also serves to show the hierarchical arrangement of data which we will see being used in the next section on data binding.

Source : Sourceforge.net