Package org.apache.struts.extras.actions

Class ActionDispatcher

java.lang.Object
org.apache.struts.extras.actions.ActionDispatcher
All Implemented Interfaces:
Serializable, Dispatcher
Direct Known Subclasses:
EventActionDispatcher
public class ActionDispatcher extends Object implements Dispatcher

Action helper class that dispatches to a public method in an Action.

This class is provided as an alternative mechanism to using DispatchAction and its various flavours and means Dispatch behaviour can be easily implemented into any Action without having to inherit from a particular super Action.

To implement dispatch behaviour in an Action class, create your custom Action as follows, along with the methods you require (and optionally "cancelled" and "unspecified" methods):

   public class MyCustomAction extends Action {

       protected ActionDispatcher dispatcher
                = new ActionDispatcher(this, ActionDispatcher.MAPPING_FLAVOR);

       public ActionForward execute(ActionMapping mapping,
                                    ActionForm form,
                                    HttpServletRequest request,
                                    HttpServletResponse response)
                           throws Exception {
           return dispatcher.execute(mapping, form, request, response);
       }
   }

It provides three flavours of determing the name of the method:

  • DEFAULT_FLAVOR - uses the parameter specified in the struts-config.xml to get the method name from the Request (equivalent to DispatchAction except uses "method" as a default if the parameter is not specified in the struts-config.xml).
  • DISPATCH_FLAVOR - uses the parameter specified in the struts-config.xml to get the method name from the Request (equivalent to DispatchAction).
  • MAPPING_FLAVOR - uses the parameter specified in the struts-config.xml as the method name (equivalent to MappingDispatchAction).
Since:
Struts 1.2.7
Version:
$Rev$ $Date$
See Also:

  • Field Details

    • DEFAULT_FLAVOR

      public static final int DEFAULT_FLAVOR
      Indicates "default" dispatch flavor.
      See Also:

    • MAPPING_FLAVOR

      public static final int MAPPING_FLAVOR
      Indicates "mapping" dispatch flavor.
      See Also:

    • DISPATCH_FLAVOR

      public static final int DISPATCH_FLAVOR
      Indicates flavor compatible with DispatchAction.
      See Also:

    • messages

      protected static MessageResources messages
      The message resources for this package.

    • actionInstance

      protected Action actionInstance
      The associated Action to dispatch to.

    • flavor

      protected int flavor
      Indicates dispatch flavor.

    • clazz

      protected Class<? extends Action> clazz
      The Class instance of this DispatchAction class.

    • methods

      protected HashMap<String,Method> 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.

    • types

      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.

  • Constructor Details

    • ActionDispatcher

      public ActionDispatcher(Action actionInstance)
      Construct an instance of this class from the supplied parameters.
      Parameters:
      actionInstance - The action instance to be invoked.

    • ActionDispatcher

      public ActionDispatcher(Action actionInstance, int flavor)
      Construct an instance of this class from the supplied parameters.
      Parameters:
      actionInstance - The action instance to be invoked.
      flavor - The flavor of dispatch to use.

  • Method Details

    • 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.
      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 forward to which control should be transferred, or null if the response has been completed.
      Throws:
      Exception - if an exception occurs

    • unspecified

      protected ActionForward unspecified(ActionMapping mapping, ActionForm form, HttpServletRequest request, HttpServletResponse response) throws Exception

      Dispatches to the target class' unspecified method, if present, otherwise throws a ServletException. Classes utilizing ActionDispatcher should provide an unspecified method if they wish to provide behavior different than throwing a ServletException.

      Parameters:
      mapping - The ActionMapping used to select this instance
      form - The optional ActionForm bean for this request (if any)
      request - The non-HTTP request we are processing
      response - The non-HTTP response we are creating
      Returns:
      The forward to which control should be transferred, or null if the response has been completed.
      Throws:
      Exception - if the application business logic throws an exception.

    • cancelled

      protected ActionForward cancelled(ActionMapping mapping, ActionForm form, HttpServletRequest request, HttpServletResponse response) throws Exception

      Dispatches to the target class' cancelled method, if present, otherwise returns null. Classes utilizing ActionDispatcher should provide a cancelled method if they wish to provide behavior different than returning null.

      Parameters:
      mapping - The ActionMapping used to select this instance
      form - The optional ActionForm bean for this request (if any)
      request - The non-HTTP request we are processing
      response - The non-HTTP response we are creating
      Returns:
      The forward to which control should be transferred, or null if the response has been completed.
      Throws:
      Exception - if the application business logic throws an exception.

    • dispatchMethod

      protected ActionForward dispatchMethod(ActionMapping mapping, ActionForm form, HttpServletRequest request, HttpServletResponse response, String name) throws Exception
      Dispatch to the specified method.
      Parameters:
      mapping - The ActionMapping used to select this instance
      form - The optional ActionForm bean for this request (if any)
      request - The non-HTTP request we are processing
      response - The non-HTTP response we are creating
      name - The name of the method to invoke
      Returns:
      The forward to which control should be transferred, or null if the response has been completed.
      Throws:
      Exception - if the application business logic throws an exception.

    • dispatchMethod

      protected ActionForward dispatchMethod(ActionMapping mapping, ActionForm form, HttpServletRequest request, HttpServletResponse response, String name, Method method) throws Exception
      Dispatch to the specified method.
      Parameters:
      mapping - The ActionMapping used to select this instance
      form - The optional ActionForm bean for this request (if any)
      request - The non-HTTP request we are processing
      response - The non-HTTP response we are creating
      name - The name of the method to invoke
      method - The method to invoke
      Returns:
      The forward to which control should be transferred, or null if the response has been completed.
      Throws:
      Exception - if the application business logic throws an exception.

    • getMethod

      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.
      Parameters:
      name - Name of the method to be introspected
      Returns:
      The method with the specified name.
      Throws:
      NoSuchMethodException - if no such method can be found

    • getParameter

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

      Returns the parameter value as influenced by the selected flavor specified for this ActionDispatcher.

      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 an error occurs.

    • 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.
      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.

    • isCancelled

      protected boolean isCancelled(HttpServletRequest request)

      Returns true if the current form's cancel button was pressed. This method will check if the Globals.CANCEL_KEY request attribute has been set, which normally occurs if the cancel button generated by CancelTag was pressed by the user in the current request. If true, validation performed by an ActionForm's validate() method will have been skipped by the controller servlet.

      Parameters:
      request - The servlet request we are processing
      Returns:
      true if the current form's cancel button was pressed; false otherwise.
      See Also:

    • dispatch

      public Object dispatch(ActionContext context) throws Exception
      Description copied from interface: Dispatcher
      Dispatches to the action referenced by the specified context.
      Specified by:
      dispatch in interface Dispatcher
      Parameters:
      context - the current action context
      Returns:
      the result type, null if the response was handled directly, or Void if the executed method has no return signature
      Throws:
      Exception - if an exception occurs
      Since:
      Struts 1.4