org.apache.struts.actions
Class EventActionDispatcher

java.lang.Object
  org.apache.struts.actions.ActionDispatcher
      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(Action action)
Constructs a new object for the specified action.

Method Summary

protected java.lang.String	getMethodName(ActionMapping mapping, ActionForm form, javax.servlet.http.HttpServletRequest request, javax.servlet.http.HttpServletResponse response, java.lang.String parameter) Returns the method name, given a parameter's value.
protected ActionForward	unspecified(ActionMapping mapping, ActionForm form, javax.servlet.http.HttpServletRequest request, javax.servlet.http.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(Action action)

Constructs a new object for the specified action.

Parameters:

action - the action

Method Detail

unspecified

protected ActionForward unspecified(ActionMapping mapping,
                                    ActionForm form,
                                    javax.servlet.http.HttpServletRequest request,
                                    javax.servlet.http.HttpServletResponse response)
                             throws java.lang.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:

java.lang.Exception - if the application business logic throws an exception.

getMethodName

protected java.lang.String getMethodName(ActionMapping mapping,
                                         ActionForm form,
                                         javax.servlet.http.HttpServletRequest request,
                                         javax.servlet.http.HttpServletResponse response,
                                         java.lang.String parameter)
                                  throws java.lang.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:

java.lang.Exception - if an error occurs.