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
execute
method is called.
When the properties of this bean have been populated, but before the
execute
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
execute
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.
Because ActionForms are JavaBeans, subclasses should also implement
Serializable
, as required by the JavaBean specification.
Some containers require that an object meet all JavaBean requirements
in order to use the introspection API upon which ActionForms rely.
getMultipartRequestHandler
public MultipartRequestHandler getMultipartRequestHandler()
Return the MultipartRequestHandler for this form
The reasoning behind this is to give form bean developers
control over the lifecycle of their multipart requests
through the use of the finish() and/or rollback() methods
of MultipartRequestHandler. This method will return
null
if this form's enctype is not
"multipart/request-data".
MultipartRequestHandler
getServlet
protected ActionServlet getServlet()
Return the controller servlet instance to which we are attached.
reset
public void reset(ActionMapping mapping,
HttpServletRequest request)
Reset all bean properties to their default state. This method is
called before the properties are repopulated by the controller servlet.
The default implementation does nothing. Subclasses should override
this method to reset all bean properties to default values.
This method is
not the appropriate place to initialize form values
for an "update" type page (this should be done in a setup Action). You mainly
need to worry about setting checkbox values to false; most of the time you
can leave this method unimplemented.
mapping
- The mapping used to select this instancerequest
- The servlet request we are processing
reset
public void reset(ActionMapping mapping,
ServletRequest request)
Reset all bean properties to their default state. This method is
called before the properties are repopulated by the controller servlet.
The default implementation attempts to forward to the HTTP
version of this method.
mapping
- The mapping used to select this instancerequest
- The servlet request we are processing
setMultipartRequestHandler
public void setMultipartRequestHandler(MultipartRequestHandler multipartRequestHandler)
Set the Handler provides to use in dealing with file uploads.
multipartRequestHandler
- The Handler to use for fileuploads.
setServlet
public void setServlet(ActionServlet servlet)
Set the controller servlet instance to which we are attached (if
servlet
is non-null), or release any allocated resources
(if servlet
is null).
servlet
- The new controller servlet, if any
validate
public ActionErrors validate(ActionMapping mapping,
HttpServletRequest request)
Validate the properties that have been set for this HTTP request,
and return an
ActionErrors
object that encapsulates any
validation errors that have been found. If no errors are found,
return
null
or an
ActionErrors
object with
no recorded error messages.
The default ipmlementation performs no validation and returns
null
. Subclasses must override this method to provide
any validation they wish to perform.
mapping
- The mapping used to select this instancerequest
- The servlet request we are processing
validate
public ActionErrors validate(ActionMapping mapping,
ServletRequest request)
Validate the properties that have been set for this non-HTTP request,
and return an
ActionErrors
object that encapsulates any
validation errors that have been found. If no errors are found, return
null
or an
ActionErrors
object with no
recorded error messages.
The default implementation attempts to forward to the HTTP version of
this method.
mapping
- The mapping used to select this instancerequest
- The servlet request we are processing