org.apache.struts.actions

Class ActionDispatcher

Known Direct Subclasses:
EventActionDispatcher

public class ActionDispatcher
extends java.lang.Object

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:

Version:
$Revision: 383720 $ $Date: 2006-03-07 00:07:59 +0000 (Tue, 07 Mar 2006) $
Since:
Struts 1.2.7

Field Summary

static int
DEFAULT_FLAVOR
Indicates "default" dispatch flavor
static int
DISPATCH_FLAVOR
Indicates flavor compatible with DispatchAction
static int
MAPPING_FLAVOR
Indicates "mapping" dispatch flavor
protected Action
actionInstance
The associated Action to dispatch to.
protected Class
clazz
The Class instance of this DispatchAction class.
protected int
flavor
Indicates dispatch flavor
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.
protected Class[]
types
The set of argument type classes for the reflected method call.

Constructor Summary

ActionDispatcher(Action actionInstance)
ActionDispatcher(Action actionInstance, int flavor)

Method Summary

protected ActionForward
cancelled(ActionMapping mapping, ActionForm form, HttpServletRequest request, HttpServletResponse response)
Dispatches to the target class' cancelled method, if present, otherwise returns null.
protected ActionForward
dispatchMethod(ActionMapping mapping, ActionForm form, HttpServletRequest request, HttpServletResponse response, String name)
Dispatch to the specified method.
protected ActionForward
dispatchMethod(ActionMapping mapping, ActionForm form, HttpServletRequest request, HttpServletResponse response, String name, Method method)
Dispatch to the specified method.
ActionForward
execute(ActionMapping mapping, ActionForm form, HttpServletRequest request, HttpServletResponse response)
Process the specified HTTP request, and create the corresponding HTTP response (or forward to another web component that will create it).
protected Method
getMethod(String name)
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)
Returns the method name, given a parameter's value.
protected String
getParameter(ActionMapping mapping, ActionForm form, HttpServletRequest request, HttpServletResponse response)
Returns the parameter value as influenced by the selected flavor specified for this ActionDispatcher.
protected boolean
isCancelled(HttpServletRequest request)
Returns true if the current form's cancel button was pressed.
protected ActionForward
unspecified(ActionMapping mapping, ActionForm form, HttpServletRequest request, HttpServletResponse response)
Dispatches to the target class' unspecified method, if present, otherwise throws a ServletException.

Field Details

DEFAULT_FLAVOR

public static final int DEFAULT_FLAVOR
Indicates "default" dispatch flavor
Field Value:
0

DISPATCH_FLAVOR

public static final int DISPATCH_FLAVOR
Indicates flavor compatible with DispatchAction
Field Value:
2

MAPPING_FLAVOR

public static final int MAPPING_FLAVOR
Indicates "mapping" dispatch flavor
Field Value:
1

actionInstance

protected Action actionInstance
The associated Action to dispatch to.

clazz

protected Class clazz
The Class instance of this DispatchAction class.

flavor

protected int flavor
Indicates dispatch flavor

log

protected static Log log
Commons Logging instance.

messages

protected static MessageResources messages
The message resources for this package.

methods

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.

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)

ActionDispatcher

public ActionDispatcher(Action actionInstance,
                        int flavor)

Method Details

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.

dispatchMethod

protected ActionForward dispatchMethod(ActionMapping mapping,
                                       ActionForm form,
                                       HttpServletRequest request,
                                       HttpServletResponse response,
                                       String name)
            throws Exception
Dispatch to the specified method.

dispatchMethod

protected ActionForward dispatchMethod(ActionMapping mapping,
                                       ActionForm form,
                                       HttpServletRequest request,
                                       HttpServletResponse response,
                                       String name,
                                       Method method)
            throws Exception
Dispatch to the specified method.

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

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

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.

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

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

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..

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