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.