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org.apache.struts.actions
Class DispatchAction
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public class DispatchAction
extends Action

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:

  • public ActionForward delete(ActionMapping mapping, ActionForm form, HttpServletRequest request, HttpServletResponse response) throws Exception
  • public ActionForward insert(ActionMapping mapping, ActionForm form, HttpServletRequest request, HttpServletResponse response) throws Exception
  • public ActionForward update(ActionMapping mapping, ActionForm form, HttpServletRequest request, HttpServletResponse response) throws Exception

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.

SinceNot specified.
Version$Rev: 3840
AuthorNot specified.
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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.
protected Class[] types
The set of argument type classes for the reflected method call.
Fields inherited from org.apache.struts.actionAction
Constructor Summary
DispatchAction()
No description provided.
Method Summary
protected ActionForward cancelled( ActionMapping mapping, ActionForm form, HttpServletRequest request, HttpServletResponse response )
Method which is dispatched to when the request is a cancel button submit.
protected ActionForward dispatchMethod( ActionMapping mapping, ActionForm form, HttpServletRequest request, HttpServletResponse response, String name )
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.

protected ActionForward unspecified( ActionMapping mapping, ActionForm form, HttpServletRequest request, HttpServletResponse response )
Method which is dispatched to when there is no value for specified request parameter included in the request.
Methods inherited from org.apache.struts.actionAction
Methods inherited from java.langObject
Field Detail
clazz
protected Class clazz
The Class instance of this DispatchAction class.
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log
protected static Log log
Commons Logging instance.
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messages
protected static MessageResources messages
The message resources for this package.
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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.
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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.
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Constructor Detail
DispatchAction
public DispatchAction ( )
No description provided.
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Method Detail
cancelled
protected ActionForward cancelled ( ActionMapping mapping, ActionForm form, HttpServletRequest request, HttpServletResponse response )
throws
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.
Since: Struts 1.2
Parameters
TypeNameDescription
ActionMapping mapping No description provided.
ActionForm form No description provided.
HttpServletRequest request No description provided.
HttpServletResponse response No description provided.
Exceptions
Exception No description provided.
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dispatchMethod
protected ActionForward dispatchMethod ( ActionMapping mapping, ActionForm form, HttpServletRequest request, HttpServletResponse response, String name )
throws
Dispatch to the specified method.
Since: Struts 1.1
Parameters
TypeNameDescription
ActionMapping mapping No description provided.
ActionForm form No description provided.
HttpServletRequest request No description provided.
HttpServletResponse response No description provided.
String name No description provided.
Exceptions
Exception No description provided.
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execute
public ActionForward execute ( ActionMapping mapping, ActionForm form, HttpServletRequest request, HttpServletResponse response )
throws
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.
Overrides method in Action
Parameters
TypeNameDescription
ActionMapping mapping The ActionMapping used to select this instance
ActionForm form The optional ActionForm bean for this request (if any)
HttpServletRequest request The HTTP request we are processing
HttpServletResponse response The HTTP response we are creating
Exceptions
Exception if an exception occurs
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getMethod
protected Method getMethod ( String name )
throws
Introspect the current class to identify a method of the specified name that accepts the same parameter types as the execute method does.
Parameters
TypeNameDescription
String name Name of the method to be introspected
Exceptions
NoSuchMethodException if no such method can be found
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getMethodName
protected String getMethodName ( ActionMapping mapping, ActionForm form, HttpServletRequest request, HttpServletResponse response, String parameter )
throws
Returns the method name, given a parameter's value.
Since: Struts 1.2
Parameters
TypeNameDescription
ActionMapping mapping The ActionMapping used to select this instance
ActionForm form The optional ActionForm bean for this request (if any)
HttpServletRequest request The HTTP request we are processing
HttpServletResponse response The HTTP response we are creating
String parameter The ActionMapping parameter's name
Exceptions
Exception No description provided.
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getParameter
protected String getParameter ( ActionMapping mapping, ActionForm form, HttpServletRequest request, HttpServletResponse response )
throws

Returns the parameter value.

Parameters
TypeNameDescription
ActionMapping mapping The ActionMapping used to select this instance
ActionForm form The optional ActionForm bean for this request (if any)
HttpServletRequest request The HTTP request we are processing
HttpServletResponse response The HTTP response we are creating
Exceptions
Exception if the parameter is missing.
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unspecified
protected ActionForward unspecified ( ActionMapping mapping, ActionForm form, HttpServletRequest request, HttpServletResponse response )
throws
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.
Parameters
TypeNameDescription
ActionMapping mapping No description provided.
ActionForm form No description provided.
HttpServletRequest request No description provided.
HttpServletResponse response No description provided.
Exceptions
Exception No description provided.
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Add your comments here.