I noticed MappingDispatchAction in Javadoc's and really liked the idea.
I wanted to use w/ Struts 1.1 though, so I did a quick and dirty
backport of it. Turned out to be really simple. I don't know if there's
any need or desire for this, but here it is. I'd provide a diff but it's
not very similar to CVS HEAD.
Nick Wesselman
Hal Leonard Corp
/*
* $Header:
/home/cvspublic/jakarta-struts/src/share/org/apache/struts/actions/MappingDispatchAction.java,v
1.8 2004/01/10 21:03:36 dgraham Exp $
* $Revision: 1.8 $
* $Date: 2004/01/10 21:03:36 $
*
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package org.apache.struts.actions;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.struts.action.ActionForm;
import org.apache.struts.action.ActionForward;
import org.apache.struts.action.ActionMapping;
/**
* <p>An abstract <strong>Action</strong> that dispatches to a public
* method that is named by the <code>parameter</code> attribute of
* the corresponding ActionMapping. This is useful for developers who prefer
* to combine many related actions into a single Action class.</p>
*
* <p>To configure the use of this action in your
* <code>struts-config.xml</code> file, create an entry like this:</p>
*
* <pre><code>
* <action path="/saveSubscription"
* type="org.example.SubscriptionAction"
* name="subscriptionForm"
* scope="request"
* input="/subscription.jsp"
* parameter="method"/>
* </code></pre>
*
* <p>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:</p>
* <ul>
* <li>public ActionForward create(ActionMapping mapping, ActionForm form,
* HttpServletRequest request, HttpServletResponse response)
* throws Exception</li>
* <li>public ActionForward edit(ActionMapping mapping, ActionForm form,
* HttpServletRequest request, HttpServletResponse response)
* throws Exception</li>
* <li>public ActionForward save(ActionMapping mapping, ActionForm form,
* HttpServletRequest request, HttpServletResponse response)
* throws Exception</li>
* <li>public ActionForward delete(ActionMapping mapping, ActionForm form,
* HttpServletRequest request, HttpServletResponse response)
* throws Exception</li>
* <li>public ActionForward list(ActionMapping mapping, ActionForm form,
* HttpServletRequest request, HttpServletResponse response)
* throws Exception</li>
* </ul>
* <p>for which you would create corresponding <action> configurations
* that reference this class:</p>
*
* <pre><code>
* <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>
* </code></pre>
*
* <p><strong>NOTE</strong> - 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.
* </p>
*
* @version $Revision: 1.1 $ $Date: 2004/02/27 20:43:59 $
* @since Struts 1.1
*/
public class MappingDispatchAction extends DispatchAction {
// -------------------------------------------------------- Class Variables
/**
* Commons Logging instance.
*/
private static Log log =
LogFactory.getLog(MappingDispatchAction.class);
// --------------------------------------------------------- Public Methods
/**
* Process the specified HTTP request, and create the corresponding HTTP
* response (or forward to another web component that will create it).
* Return an <code>ActionForward</code> instance describing where and how
* control should be forwarded, or <code>null</code> if the response has
* already been completed.
*
* This method dispatches the request to other methods of
* <code>MappingDispatchAction</code> using the 'parameter' attribute of
* <code>ActionMapping</code> and Java Introspection.
*
* @param mapping The ActionMapping used to select this instance
* @param form The optional ActionForm bean for this request (if any)
* @param request The HTTP request we are processing
* @param response The HTTP response we are creating
*
* @return Return an <code>ActionForward</code> instance describing where
* and how control should be forwarded, or <code>null</code> if
* the response has already been completed.
*
* @exception Exception if an exception occurs
*/
public ActionForward execute(
ActionMapping mapping,
ActionForm form,
HttpServletRequest request,
HttpServletResponse response)
throws Exception {
//Identify the method name within the mapping parameter
String parameter = mapping.getParameter();
if (parameter == null) {
String message =
messages.getMessage("dispatch.handler", mapping.getPath());
log.error(message);
response.sendError(HttpServletResponse.SC_INTERNAL_SERVER_ERROR,
message);
return (null);
}
//Invoke the named method, and return the result
return dispatchMethod(mapping, form, request, response, parameter);
}
}
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