org.apache.struts.actions

Class MappingDispatchAction


public class MappingDispatchAction
extends DispatchAction

An abstract Action that dispatches to a public method that is named by the parameter attribute of the corresponding ActionMapping. This is useful for developers who prefer to combine many related actions into a single Action class.

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="method"/>
 

where 'method' is the name of a method in your subclass of MappingDispatchAction that has the same signature (other than method name) of the standard Action.execute method. For example, you might combine the methods for managing a subscription into a single MappingDispatchAction class using the following methods:

for which you would create corresponding <action> configurations that reference this class:


  <action path="/createSubscription" 
          type="org.example.SubscriptionAction"
          parameter="create">
      <forward name="success" path="/editSubscription.jsp"/>
  </action>
 
  <action path="/editSubscription" 
          type="org.example.SubscriptionAction"
          parameter="edit">
      <forward name="success" path="/editSubscription.jsp"/>
  </action>

  <action path="/saveSubscription" 
          type="org.example.SubscriptionAction" 
          parameter="save"
          name="subscriptionForm" 
          validate="true" 
          input="/editSubscription.jsp" 
          scope="request">
      <forward name="success" path="/savedSubscription.jsp"/>
  </action>

  <action path="/deleteSubscription" 
          type="org.example.SubscriptionAction"
          name="subscriptionForm"
          scope="request"
          input="/subscription.jsp"
          parameter="delete">
      <forward name="success" path="/deletedSubscription.jsp"/>
  </action>

  <action path="/listSubscriptions" 
          type="org.example.SubscriptionAction"
          parameter="list">
      <forward name="success" path="/subscriptionList.jsp"/>
  </action>
 

NOTE - Unlike DispatchAction, mapping characteristics may differ between the various handlers, so you can combine actions in the same class that, for example, differ in their use of forms or validation. Also, a request parameter, which would be visible to the application user, is not required to enable selection of the handler method.

Version:
$Rev: 54929 $ $Date: 2004-10-16 17:38:42 +0100 (Sat, 16 Oct 2004) $
Since:
Struts 1.2

Field Summary

private static Log
log
Commons Logging instance.

Fields inherited from class org.apache.struts.actions.DispatchAction

clazz, log, messages, methods, types

Fields inherited from class org.apache.struts.action.Action

defaultLocale, servlet, token

Method Summary

ActionForward
execute(ActionMapping mapping, ActionForm form, HttpServletRequest request, HttpServletResponse response)
Process the specified HTTP request, and create the corresponding HTTP response (or forward to another web component that will create it).
protected String
getMethodName(ActionMapping mapping, ActionForm form, HttpServletRequest request, HttpServletResponse response, String parameter)
Returns the method name, given a parameter's value.
protected ActionForward
unspecified(ActionMapping mapping, ActionForm form, HttpServletRequest request, HttpServletResponse response)
Method which is dispatched to when there is no value for the parameter in the ActionMapping.

Methods inherited from class org.apache.struts.actions.DispatchAction

cancelled, dispatchMethod, execute, getMethod, getMethodName, getParameter, unspecified

Methods inherited from class org.apache.struts.action.Action

addErrors, addMessages, execute, execute, generateToken, getDataSource, getDataSource, getErrors, getLocale, getMessages, getResources, getResources, getServlet, isCancelled, isTokenValid, isTokenValid, resetToken, saveErrors, saveErrors, saveErrors, saveMessages, saveMessages, saveToken, setLocale, setServlet

Field Details

log

private static Log log
Commons Logging instance.

Method Details

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. This method dispatches the request to other methods of MappingDispatchAction using the 'parameter' attribute of ActionMapping and Java Introspection.
Overrides:
execute in interface DispatchAction
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
Returns:
Return an ActionForward instance describing where and how control should be forwarded, or null if the response has already been completed.

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.
Overrides:
getMethodName in interface DispatchAction
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.
Since:
Struts 1.2.0

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 the parameter in the ActionMapping. Subclasses of MappingDispatchAction should override this method if they wish to provide default behavior different than throwing a ServletException.
Overrides:
unspecified in interface DispatchAction
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
Returns:
Return an ActionForward instance describing where and how control should be forwarded, or null if the response has already been completed.

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