Apache Struts API Documentation: Class MappingDispatchAction

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:

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

log

private static org.apache.commons.logging.Log log

Commons Logging instance.

MappingDispatchAction

public MappingDispatchAction()

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