Cisco Cisco Unified Customer Voice Portal 10.5(1) Entwickleranleitung

PPENDIX

OICE

OUNDATION

LASSES

ISCO

CVP V

OICE

XML 3.1

Programmer

Guide

also versions of the VoiceXML standard. There are separate VFCs for VoiceXML version 1.0
and version 2.0, and the similarities are encapsulated in a common base class. Figure 12-1 shows
this graphically with the

VForm

class. The main

VForm

class extends the

VRoot

class and is itself

extended by

VFormV1

and

VFormV2

, representing VoiceXML 1.0 and 2.0 compliance. Luckily,

there are only a few differences between these versions, so the developer can still do most coding
to the base

VForm

class. The Gateway Adapters introduce VFCs that extend

VFormV1

VFormV2

depending on whether the voice browser it supports is compatible with VoiceXML 1.0 or 2.0.

Figure 12-1

The last concept is that VFC objects are not instantiated using the

new

keyword. A static factory

method named

getNew

is used instead. The reason for this is related to the abstraction of the

voice browser differences. As mentioned previously, a developer need only code using the base
VFC classes. At runtime, the factory methods used to instantiate VFC classes actually returns the
appropriate voice browser-specific VFC (for example,

VFormFoo

in the example in Figure 12-1).

But since the developer treats the return object as the base VFC, that object is downcasted. This
is the heart of the VFC abstraction design. Since all VFC derivative classes extend their base
VFCs, a developer need only code to the base VFCs and that automatically makes their code
compatible with any voice browser represented by a Gateway Adapter.

In order to identify which voice browser VFC to return, every factory method must include as its
first argument an instance of

VPreference

, while a VFC class, does not match to

a VoiceXML tag, it is used instead to hold preferences made by the user in CVP VoiceXML
Studio for the application, such as the voice browser and default audio path. By passing this
object to all factory methods, the appropriate object can be returned. The

VPreference

instance

is automatically created for the developer and made available through the Session API passed to
voice elements, hotevents, or call end classes.