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## org.apache.struts.actions
Class MappingDispatchAction

    java.lang.Object
      org.apache.struts.action.Action
          org.apache.struts.actions.BaseAction
              org.apache.struts.actions.DispatchAction
                  org.apache.struts.actions.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:

- public ActionForward create(ActionMapping mapping, ActionForm form, HttpServletRequest request, HttpServletResponse response) throws Exception
- public ActionForward edit(ActionMapping mapping, ActionForm form, HttpServletRequest request, HttpServletResponse response) throws Exception
- public ActionForward save(ActionMapping mapping, ActionForm form, HttpServletRequest request, HttpServletResponse response) throws Exception
- public ActionForward delete(ActionMapping mapping, ActionForm form, HttpServletRequest request, HttpServletResponse response) throws Exception
- public ActionForward list(ActionMapping mapping, ActionForm form, HttpServletRequest request, HttpServletResponse response) throws Exception

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.

Since:
  Struts 1.2
Version:
  $Rev: 480570 $ $Date: 2006-11-29 07:39:37 -0600 (Wed, 29 Nov 2006) $

Field Summary

Fields inherited from class org.apache.struts.actions.DispatchAction
`clazz, methods, types`

Fields inherited from class org.apache.struts.actions.BaseAction
`messages`

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

Constructor Summary
`MappingDispatchAction()`

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 String` | `getParameter(ActionMapping mapping, ActionForm form, HttpServletRequest request, HttpServletResponse response)` Returns the parameter 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, getMethod`

Methods inherited from class org.apache.struts.action.Action
`addErrors, addMessages, execute, generateToken, getErrors, getLocale, getMessages, getResources, getResources, getServlet, isCancelled, isTokenValid, isTokenValid, resetToken, saveErrors, saveErrors, saveMessages, saveMessages, saveToken, setLocale, setServlet`

Methods inherited from class java.lang.Object
`clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

Constructor Detail

### MappingDispatchAction

    public MappingDispatchAction()

Method Detail

### 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 class `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.
  Throws:
    `Exception` - if an exception occurs

### 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 class `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.
  Throws:
    `Exception` - if an exception occurs

### getParameter

    protected String getParameter(ActionMapping mapping,
                                  ActionForm form,
                                  HttpServletRequest request,
                                  HttpServletResponse response)
                           throws Exception

  Returns the parameter value.

  Overrides:
    `getParameter` in class `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:
    The `ActionMapping` parameter's value
  Throws:
    `Exception` - if the parameter is missing.

### 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 class `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.
  Throws:
    `Exception` - if an error occurs
  Since:
    Struts 1.2.0

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