The previous chapter described components and explained how to add them
to a web page. This chapter provides information on adding more
functionality to the components through converters, listeners, and
Converters are used to convert data that is received from the input
components. Converters allow an application to bring the strongly typed
features of the Java programming language into the String-based world of
HTTP servlet programming.
Listeners are used to listen to the events happening in the page and
perform actions as defined.
Validators are used to validate the data that is received from the
input components. Validators allow an application to express constraints
on form input data to ensure that the necessary requirements are met
before the input data is processed.
The following topics are addressed here: