A transition context stores and validates input data before the
processor commits valid data to the process context. To do this, a
transition context retains the input data of a form along with their
related data elements and any ErrorInfo objects obtained when validating
the data. This provides the following benefits:
- Security. A transition context acts as a specification
of the input from a form. The system ignores any submitted information
that is not in the transition context definition. This protects the
application by preventing unexpected data from being inserted into
the application context.
- Data filtering. A transition context defines the set of
data related to a specific action in a page. This provides you with
the ability to filter data items held within a page.
- Data integrity. A transition context preserves application
data integrity because the processor only copies validated data into
the application context.
- Transient error information. The life cycle of a transition
context is very short and the toolkit takes advantage of this in its
management of error information. The processor attaches an ErrorInfo
object to any data elements in the transition context that are in
error so that JSP code can use this object. Once the processor discards
the transition context, it also discards these ErrorInfo objects.
By preserving input data in a transition context, the processor
is able to restore input data should a user return to a canceled page.