org.apache.struts.actions
Class MappingDispatchAction

java.lang.Object
  |
  +--org.apache.struts.action.Action
        |
        +--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:

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: 54929 $ $Date: 2004-10-16 17:38:42 +0100 (Sat, 16 Oct 2004) $

Field Summary
private static org.apache.commons.logging.Log log
          Commons Logging instance.
 
Fields inherited from class org.apache.struts.actions.DispatchAction
clazz, messages, methods, types
 
Fields inherited from class org.apache.struts.action.Action
defaultLocale, servlet, token
 
Constructor Summary
MappingDispatchAction()
           
 
Method Summary
 ActionForward execute(ActionMapping mapping, ActionForm form, javax.servlet.http.HttpServletRequest request, javax.servlet.http.HttpServletResponse response)
          Process the specified HTTP request, and create the corresponding HTTP response (or forward to another web component that will create it).
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)
          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, getParameter
 
Methods inherited from class org.apache.struts.action.Action
addErrors, addMessages, execute, generateToken, getDataSource, getDataSource, getErrors, getLocale, getMessages, getResources, getResources, getServlet, isCancelled, isTokenValid, isTokenValid, resetToken, saveErrors, saveErrors, saveErrors, saveMessages, saveMessages, saveToken, setLocale, setServlet
 
Methods inherited from class java.lang.Object
, clone, equals, finalize, getClass, hashCode, notify, notifyAll, registerNatives, toString, wait, wait, wait
 

Field Detail

log

private static org.apache.commons.logging.Log log
Commons Logging instance.
Constructor Detail

MappingDispatchAction

public MappingDispatchAction()
Method Detail

execute

public ActionForward execute(ActionMapping mapping,
                             ActionForm form,
                             javax.servlet.http.HttpServletRequest request,
                             javax.servlet.http.HttpServletResponse response)
                      throws java.lang.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:
java.lang.Exception - if an exception occurs

unspecified

protected ActionForward unspecified(ActionMapping mapping,
                                    ActionForm form,
                                    javax.servlet.http.HttpServletRequest request,
                                    javax.servlet.http.HttpServletResponse response)
                             throws java.lang.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:
java.lang.Exception - if an exception occurs

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 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


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