Bound Values in OA framework - I

A web bean in OAF(UIX) consists of

• Indexed Children
• Named Children
• Attributes.

Attributes can be specified at design time in which case it will be a simple name/value pair and value of that attribute will be static. Attribute value can also be determined during run time. If the attribute value has to be determined runtime it must be bound to a data source. When OAF(UIX) is building/rendering these UI nodes it establishes a context called rendering context. And to acheive this runtime behavior we get the data source from this rendering context.

Lets convert the above statement in English Language to Java language

RenderingContext - Interface representing the context when OAF(UIX) builds(renders) the UI nodes.
BoundValue - Is a simple interface with a single method getValue(RenderingContext context). It is left to the implementation of getValue() method to achieve the run time behavior based on rendering context object.

So OAWebBean (MutableUINode to be precise) have a method to set attribute value.

public void setAttributeValue(AttributeKey attrKey,Object value)

Value can be any implementation of BoundValue interface if it must be determined at runtime.

And at run time, when OAF(UIX) uses getAttributeValue(RenderingContext context, AttributeKey key), a typical code might look like

if ((value instanceof BoundValue))
{
return ((BoundValue)value).getValue(context);
}

Generally the parameters that determine the run time value will be passed to the constructor of BoundValue implementing object. For example DataBoundValue is a implementation of BoundValue which reads value based on DataObject in the context. DataObject is very simple interface to extract arbitarily structured data.

So one of the construtor of that Class is

public DataBoundValue(
Object select
)


where the parameter, select, is used to get the DataObject from RenderingContext.

And getValue() method implementation will be simple

return context.getCurrentDataObject().selectValue(context, select);