Chapter 7. Validating Input
There are two types of input validation
you must consider in any application: syntactic
and semantic validation. A form field value that
represents a date, for instance, must be written in a certain format
(i.e., be syntactically correct) in order to be interpreted by the
application. It may also have to follow other rules (i.e., be
semantically correct) to be accepted, e.g., be a date in the future
or later than another date.
In JSF, components perform syntactic validation typically during the
conversion from a request parameter string value to the native type
of the business data property bound to the component. For semantic
validation, you can attach validators to the components. JSF comes
with a set of standard validators for the most common validation
needs and lets you develop custom validators for more complex rules.
We'll look at both alternatives in this chapter.