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Concepts
For Java client development, JDeveloper provides JClient,
a client framework for building Java applications and applets for business components.
JClient uses the model-view-controller (MVC) design pattern to allow you to
bind standard Swing controls or any third party model-based controls to BC4J
data sources. This approach is multi-tiered and modular; the MVC design pattern
identifies three entities, each operating in a different logical layer within
the application space:
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Model: A back-end representation of enterprise data and business
logic, the model also maintains data about the state of the application.
In many cases, the model is a logical representation of a real-world process.
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View: The front-end presentation layer that renders the model for
end-users. Views also provide user interfaces for accessing the enterprise
data represented by the model.
- Controller: The middle tier of the MVC pattern.
The controller defines application behavior, selecting views for presentation
and capturing a user's interactions with views and routing them as commands
to the model.
The MVC design pattern defines a clear separation of application
logic, presentation details, business rules and data. As a result, multiple
clients, displays, and devices can use the same application and business rules
to work with the same data. The following figure shows how model, view, and
controller interact.
JClient provides model objects for Swing controls that are
responsible for marshalling interaction between the Swing controls and the business
component datasource's rowset iterator. The JClient implementation of Swing
models are known as control bindings.
The UI components in the JClient application bind directly
to view objects in the BC4J tier. For example, a JClient databound panel, might
have a text field (JTextField) for the First name and Last name that allows
the user to view and modify business component attribute values.
The type of control binding used for a given Swing control
depends on the actions performed by the control. In some cases, controls work
with multiple control bindings that define different interactions.
JClient also provides a number of composite controls, making
it easy to design Java clients with richer functionality than the standard Swing
controls provide. Using JClient's design-time wizards you can quickly generate
data-aware forms, which you can then customize with JDeveloper's user interface
design tools.
For example, a JCheckBox is a Swing component which has a
defined Model, View, and Controller. When the user interacts with the controller
by clicking the checkbox, the controller notifies the model that it should change
its state (from false to true or the reverse). The view, which is listening
for changes in the state of the model, can then update itself (for example,
by making the checkbox appear selected). An important point about this architecture
is that the model is not aware of the view or views displaying it, nor of the
controller(s) being used to update it.
BC4J makes it easy to bind JSP, Java Swing, wireless, and
other XML clients to business components. The tier-independent programming model
ensures that the same application can be bound to different user interfaces
without changing any code in the business logic tier. For JSP/Servlet applications,
JDeveloper provides the BC4J Data Tag Library, a set of JSP 1.1 compliant tags
for binding JSP pages to Business Components data sources. The BC4J data tags
make it easy to design and build JSP database applications with complete control
of both the HTML design and the database access operations.
When using the data tags, you don't have to write large amounts
of Java code to interact with BC4J data or customize the user interface. The
client JSP application can mostly be comprised of HTML and JSP tags, giving
JSP you the flexibility to use your favorite visual HTML editors in conjunction
with JDeveloper to design the exact appearance of your JSP application.
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