An ActionForm is a JavaBean optionally associated with one or more ActionMappings. Such a bean will have had its properties initialized from the corresponding request parameters before the corresonding action's perform() method is called. When the properties of this bean have been POPULATED, but before the perform() method of the action is called, this bean's VALIDATE() method will be called, which gives the bean a chance to verify that the properties submitted by the user are correct and VALID. If this method finds problems, it returns an error messages object that encapsulates those problems, and the controller servlet will return control to the corresponding input form. OTHERWISE, the validate() method returns null(), indicating that everything is acceptable and the corresponding Action's perform() method should be called. This class must be subclassed in order to be instantiated. Subclasses should provide property getter and setter methods for all of the bean properties they wish to expose, plus OVERRIDE any of the public or protected methods for which they wish to provide modified functionality.

An ActionForm is a JavaBean optionally associated with one or more ActionMappings. Such a bean will have had its properties initialized from the corresponding request parameters before the corresonding action's perform() method is called. When the properties of this bean have been populated, but before the perform() method of the action is called, this bean's validate() method will be called, which gives the bean a chance to verify that the properties submitted by the user are correct and valid. If this method finds problems, it returns an error messages object that encapsulates those problems, and the controller servlet will return control to the corresponding input form. Otherwise, the validate() method returns null(), indicating that everything is acceptable and the corresponding Action's perform() method should be called. This class must be subclassed in order to be instantiated. Subclasses should provide property getter and setter methods for all of the bean properties they wish to expose, plus override any of the public or protected methods for which they wish to provide modified functionality.