org.apache.struts.actions
Class EventActionDispatcher

java.lang.Object
  extended by org.apache.struts.actions.ActionDispatcher
      extended by org.apache.struts.actions.EventActionDispatcher

public class EventActionDispatcher
extends ActionDispatcher

An Action helper class that dispatches to to one of the public methods that are named in the parameter attribute of the corresponding ActionMapping and matches a submission parameter. This is useful for developers who prefer to use many submit buttons, images, or submit links on a single form and whose related actions exist in a single Action class.

The method(s) in the associated Action must have the same signature (other than method name) of the standard Action.execute method.

To configure the use of this action in your struts-config.xml file, create an entry like this:


   <action path="/saveSubscription"
           type="org.example.SubscriptionAction"
           name="subscriptionForm"
          scope="request"
          input="/subscription.jsp"
      parameter="save,back,recalc=recalculate,default=save"/>
 

where parameter contains three possible methods and one default method if nothing matches (such as the user pressing the enter key).

For utility purposes, you can use the key=value notation to alias methods so that they are exposed as different form element names, in the event of a naming conflict or otherwise. In this example, the recalc button (via a request parameter) will invoke the recalculate method. The security-minded person may find this feature valuable to obfuscate and not expose the methods.

The default key is purely optional. If this is not specified and no parameters match the list of method keys, null is returned which means the unspecified method will be invoked.

The order of the parameters are guaranteed to be iterated in the order specified. If multiple buttons were accidently submitted, the first match in the list will be dispatched.

To implement this dispatch behaviour in an Action, class create your custom Action as follows, along with the methods you require (and optionally "cancelled" and "unspecified" methods):

   public class MyCustomAction extends Action {

       protected ActionDispatcher dispatcher = new EventActionDispatcher(this);

       public ActionForward execute(ActionMapping mapping,
                                    ActionForm form,
                                    HttpServletRequest request,
                                    HttpServletResponse response)
                           throws Exception {
           return dispatcher.execute(mapping, form, request, response);
       }
   }
 

Since:
Struts 1.2.9

Field Summary
 
Fields inherited from class org.apache.struts.actions.ActionDispatcher
actionInstance, clazz, DEFAULT_FLAVOR, DISPATCH_FLAVOR, flavor, log, MAPPING_FLAVOR, messages, methods, types
 
Constructor Summary
EventActionDispatcher(org.apache.struts.action.Action action)
          Constructs a new object for the specified action.
 
Method Summary
protected  String getMethodName(org.apache.struts.action.ActionMapping mapping, org.apache.struts.action.ActionForm form, HttpServletRequest request, HttpServletResponse response, String parameter)
          Returns the method name, given a parameter's value.
protected  org.apache.struts.action.ActionForward unspecified(org.apache.struts.action.ActionMapping mapping, org.apache.struts.action.ActionForm form, HttpServletRequest request, HttpServletResponse response)
          Dispatches to the target class' unspecified method, if present, otherwise throws a ServletException.
 
Methods inherited from class org.apache.struts.actions.ActionDispatcher
cancelled, dispatchMethod, dispatchMethod, execute, getMethod, getParameter, isCancelled
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Constructor Detail

EventActionDispatcher

public EventActionDispatcher(org.apache.struts.action.Action action)
Constructs a new object for the specified action.

Parameters:
action - the action
Method Detail

unspecified

protected org.apache.struts.action.ActionForward unspecified(org.apache.struts.action.ActionMapping mapping,
                                                             org.apache.struts.action.ActionForm form,
                                                             HttpServletRequest request,
                                                             HttpServletResponse response)
                                                      throws Exception

Dispatches to the target class' unspecified method, if present, otherwise throws a ServletException. Classes utilizing EventActionDispatcher should provide an unspecified method if they wish to provide behavior different than throwing a ServletException.

Overrides:
unspecified in class ActionDispatcher
Parameters:
mapping - The ActionMapping used to select this instance
form - The optional ActionForm bean for this request (if any)
request - The non-HTTP request we are processing
response - The non-HTTP response we are creating
Returns:
The forward to which control should be transferred, or null if the response has been completed.
Throws:
Exception - if the application business logic throws an exception.

getMethodName

protected String getMethodName(org.apache.struts.action.ActionMapping mapping,
                               org.apache.struts.action.ActionForm form,
                               HttpServletRequest request,
                               HttpServletResponse response,
                               String parameter)
                        throws Exception
Returns the method name, given a parameter's value.

Overrides:
getMethodName in class ActionDispatcher
Parameters:
mapping - The ActionMapping used to select this instance
form - The optional ActionForm bean for this request (if any)
request - The HTTP request we are processing
response - The HTTP response we are creating
parameter - The ActionMapping parameter's name
Returns:
The method's name.
Throws:
Exception - if an error occurs.


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