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org.apache.struts.actions
abstract public class: DispatchAction [javadoc | source]
java.lang.Object
   org.apache.struts.action.Action
      org.apache.struts.actions.DispatchAction

Direct Known Subclasses:
    LookupDispatchAction, EventDispatchAction, MappingDispatchAction

An abstract Action that dispatches to a public method that is named by the request parameter whose name is specified by the parameter property of the corresponding ActionMapping. This Action is useful for developers who prefer to combine many similar actions into a single Action class, in order to simplify their application design.

To configure the use of this action in your struts-config.xml file, create an entry like this:

<action path="/saveSubscription" type="org.apache.struts.actions.DispatchAction" name="subscriptionForm" scope="request" input="/subscription.jsp" parameter="method"/>

which will use the value of the request parameter named "method" to pick the appropriate "execute" method, which must have the same signature (other than method name) of the standard Action.execute method. For example, you might have the following three methods in the same action:

and call one of the methods with a URL like this:

http://localhost:8080/myapp/saveSubscription.do?method=update

NOTE - All of the other mapping characteristics of this action must be shared by the various handlers. This places some constraints over what types of handlers may reasonably be packaged into the same DispatchAction subclass.

NOTE - If the value of the request parameter is empty, a method named unspecified is called. The default action is to throw an exception. If the request was cancelled (a html:cancel button was pressed), the custom handler cancelled will be used instead. You can also override the getMethodName method to override the action's default handler selection.

Field Summary
protected  Class clazz    The Class instance of this DispatchAction class. 
protected static  Log log    Commons Logging instance. 
protected static  MessageResources messages    The message resources for this package. 
protected  HashMap methods    The set of Method objects we have introspected for this class, keyed by method name. This collection is populated as different methods are called, so that introspection needs to occur only once per method name. 
protected  Class[] types    The set of argument type classes for the reflected method call. These are the same for all calls, so calculate them only once. 
Method from org.apache.struts.actions.DispatchAction Summary:
cancelled,   dispatchMethod,   execute,   getMethod,   getMethodName,   getParameter,   unspecified
Methods from java.lang.Object:
clone,   equals,   finalize,   getClass,   hashCode,   notify,   notifyAll,   toString,   wait,   wait,   wait
Method from org.apache.struts.actions.DispatchAction Detail:
 protected ActionForward cancelled(ActionMapping mapping,
    ActionForm form,
    HttpServletRequest request,
    HttpServletResponse response) throws Exception 
    Method which is dispatched to when the request is a cancel button submit. Subclasses of DispatchAction should override this method if they wish to provide default behavior different than returning null.
 protected ActionForward dispatchMethod(ActionMapping mapping,
    ActionForm form,
    HttpServletRequest request,
    HttpServletResponse response,
    String name) throws Exception 
    Dispatch to the specified method.
 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.
 protected Method getMethod(String name) throws NoSuchMethodException 
    Introspect the current class to identify a method of the specified name that accepts the same parameter types as the execute method does.
 protected String getMethodName(ActionMapping mapping,
    ActionForm form,
    HttpServletRequest request,
    HttpServletResponse response,
    String parameter) throws Exception 
    Returns the method name, given a parameter's value.
 protected String getParameter(ActionMapping mapping,
    ActionForm form,
    HttpServletRequest request,
    HttpServletResponse response) throws Exception 

    Returns the parameter value.

 protected ActionForward unspecified(ActionMapping mapping,
    ActionForm form,
    HttpServletRequest request,
    HttpServletResponse response) throws Exception 
    Method which is dispatched to when there is no value for specified request parameter included in the request. Subclasses of DispatchAction should override this method if they wish to provide default behavior different than throwing a ServletException.