org.apache.struts.actions
Class ActionDispatcher

java.lang.Object
  extended by org.apache.struts.actions.ActionDispatcher
Direct Known Subclasses:
EventActionDispatcher

public class ActionDispatcher
extends 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:

Since:
Struts 1.2.7
Version:
$Rev: 471754 $ $Date: 2006-11-06 08:55:09 -0600 (Mon, 06 Nov 2006) $

Field Summary
protected  org.apache.struts.action.Action actionInstance
          The associated Action to dispatch to.
protected  Class clazz
          The Class instance of this DispatchAction class.
static int DEFAULT_FLAVOR
          Indicates "default" dispatch flavor.
static int DISPATCH_FLAVOR
          Indicates flavor compatible with DispatchAction.
protected  int flavor
          Indicates dispatch flavor.
protected static Log log
          Commons Logging instance.
static int MAPPING_FLAVOR
          Indicates "mapping" dispatch flavor.
protected static org.apache.struts.util.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(org.apache.struts.action.Action actionInstance)
          Construct an instance of this class from the supplied parameters.
ActionDispatcher(org.apache.struts.action.Action actionInstance, int flavor)
          Construct an instance of this class from the supplied parameters.
 
Method Summary
protected  org.apache.struts.action.ActionForward cancelled(org.apache.struts.action.ActionMapping mapping, org.apache.struts.action.ActionForm form, HttpServletRequest request, HttpServletResponse response)
          Dispatches to the target class' cancelled method, if present, otherwise returns null.
protected  org.apache.struts.action.ActionForward dispatchMethod(org.apache.struts.action.ActionMapping mapping, org.apache.struts.action.ActionForm form, HttpServletRequest request, HttpServletResponse response, String name)
          Dispatch to the specified method.
protected  org.apache.struts.action.ActionForward dispatchMethod(org.apache.struts.action.ActionMapping mapping, org.apache.struts.action.ActionForm form, HttpServletRequest request, HttpServletResponse response, String name, Method method)
          Dispatch to the specified method.
 org.apache.struts.action.ActionForward execute(org.apache.struts.action.ActionMapping mapping, org.apache.struts.action.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(org.apache.struts.action.ActionMapping mapping, org.apache.struts.action.ActionForm form, HttpServletRequest request, HttpServletResponse response, String parameter)
          Returns the method name, given a parameter's value.
protected  String getParameter(org.apache.struts.action.ActionMapping mapping, org.apache.struts.action.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  org.apache.struts.action.ActionForward unspecified(org.apache.struts.action.ActionMapping mapping, org.apache.struts.action.ActionForm form, HttpServletRequest request, HttpServletResponse response)
          Dispatches to the target class' unspecified method, if present, otherwise throws a ServletException.
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Field Detail

DEFAULT_FLAVOR

public static final int DEFAULT_FLAVOR
Indicates "default" dispatch flavor.

See Also:
Constant Field Values

MAPPING_FLAVOR

public static final int MAPPING_FLAVOR
Indicates "mapping" dispatch flavor.

See Also:
Constant Field Values

DISPATCH_FLAVOR

public static final int DISPATCH_FLAVOR
Indicates flavor compatible with DispatchAction.

See Also:
Constant Field Values

log

protected static Log log
Commons Logging instance.


messages

protected static org.apache.struts.util.MessageResources messages
The message resources for this package.


actionInstance

protected org.apache.struts.action.Action actionInstance
The associated Action to dispatch to.


flavor

protected int flavor
Indicates dispatch flavor.


clazz

protected Class clazz
The Class instance of this DispatchAction class.


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 Detail

ActionDispatcher

public ActionDispatcher(org.apache.struts.action.Action actionInstance)
Construct an instance of this class from the supplied parameters.

Parameters:
actionInstance - The action instance to be invoked.

ActionDispatcher

public ActionDispatcher(org.apache.struts.action.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 Detail

execute

public org.apache.struts.action.ActionForward execute(org.apache.struts.action.ActionMapping mapping,
                                                      org.apache.struts.action.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 org.apache.struts.action.ActionForward unspecified(org.apache.struts.action.ActionMapping mapping,
                                                             org.apache.struts.action.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 org.apache.struts.action.ActionForward cancelled(org.apache.struts.action.ActionMapping mapping,
                                                           org.apache.struts.action.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 org.apache.struts.action.ActionForward dispatchMethod(org.apache.struts.action.ActionMapping mapping,
                                                                org.apache.struts.action.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 org.apache.struts.action.ActionForward dispatchMethod(org.apache.struts.action.ActionMapping mapping,
                                                                org.apache.struts.action.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(org.apache.struts.action.ActionMapping mapping,
                              org.apache.struts.action.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(org.apache.struts.action.ActionMapping mapping,
                               org.apache.struts.action.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:
org.apache.struts.taglib.html.CancelTag


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