An abstract
Action that dispatches to a public
method that is named by the request parameter whose name is specified
by the
parameter
property of the corresponding
ActionMapping. This Action is useful for developers who prefer to
combine many similar actions into a single Action class, in order to
simplify their application design.
To configure the use of this action in your
struts-config.xml
file, create an entry like this:
<action path="/saveSubscription"
type="org.apache.struts.actions.DispatchAction"
name="subscriptionForm"
scope="request"
input="/subscription.jsp"
parameter="method"/>
which will use the value of the request parameter named "method"
to pick the appropriate "execute" method, which must have the same
signature (other than method name) of the standard Action.execute
method. For example, you might have the following three methods in the
same action:
- public ActionForward delete(ActionMapping mapping, ActionForm form,
HttpServletRequest request, HttpServletResponse response)
throws Exception
- public ActionForward insert(ActionMapping mapping, ActionForm form,
HttpServletRequest request, HttpServletResponse response)
throws Exception
- public ActionForward update(ActionMapping mapping, ActionForm form,
HttpServletRequest request, HttpServletResponse response)
throws Exception
and call one of the methods with a URL like this:
http://localhost:8080/myapp/saveSubscription.do?method=update
NOTE - All of the other mapping characteristics of
this action must be shared by the various handlers. This places some
constraints over what types of handlers may reasonably be packaged into
the same
DispatchAction
subclass.
NOTE - If the value of the request parameter is empty,
a method named
unspecified
is called. The default action is
to throw an exception. If the request was cancelled (a
html:cancel
button was pressed), the custom handler
cancelled
will be used instead.
You can also override the
getMethodName
method to override the action's
default handler selection.
cancelled
protected ActionForward cancelled(ActionMapping mapping,
ActionForm form,
HttpServletRequest request,
HttpServletResponse response)
throws Exception
Method which is dispatched to when the request is a cancel button submit.
Subclasses of DispatchAction
should override this method if
they wish to provide default behavior different than returning null.
dispatchMethod
protected ActionForward dispatchMethod(ActionMapping mapping,
ActionForm form,
HttpServletRequest request,
HttpServletResponse response,
String name)
throws Exception
Dispatch to the specified method.
execute
public ActionForward execute(ActionMapping mapping,
ActionForm form,
HttpServletRequest request,
HttpServletResponse response)
throws Exception
Process the specified HTTP request, and create the corresponding HTTP
response (or forward to another web component that will create it).
Return an ActionForward
instance describing where and how
control should be forwarded, or null
if the response has
already been completed.
- execute in interface Action
mapping
- The ActionMapping used to select this instanceform
- The optional ActionForm bean for this request (if any)request
- The HTTP request we are processingresponse
- The HTTP response we are creating
getMethod
protected Method getMethod(String name)
throws NoSuchMethodException
Introspect the current class to identify a method of the specified
name that accepts the same parameter types as the execute
method does.
name
- Name of the method to be introspected
getMethodName
protected String getMethodName(ActionMapping mapping,
ActionForm form,
HttpServletRequest request,
HttpServletResponse response,
String parameter)
throws Exception
Returns the method name, given a parameter's value.
mapping
- The ActionMapping used to select this instanceform
- The optional ActionForm bean for this request (if any)request
- The HTTP request we are processingresponse
- The HTTP response we are creatingparameter
- The ActionMapping
parameter's name
getParameter
protected String getParameter(ActionMapping mapping,
ActionForm form,
HttpServletRequest request,
HttpServletResponse response)
throws Exception
Returns the parameter value.
mapping
- The ActionMapping used to select this instanceform
- The optional ActionForm bean for this request (if any)request
- The HTTP request we are processingresponse
- The HTTP response we are creating
- The
ActionMapping
parameter's value
unspecified
protected ActionForward unspecified(ActionMapping mapping,
ActionForm form,
HttpServletRequest request,
HttpServletResponse response)
throws Exception
Method which is dispatched to when there is no value for specified
request parameter included in the request. Subclasses of
DispatchAction
should override this method if they wish
to provide default behavior different than throwing a ServletException.