Package org.apache.struts.extras.actions

Class DispatchAction

java.lang.Object
org.apache.struts.action.Action
org.apache.struts.extras.actions.BaseAction
org.apache.struts.extras.actions.DispatchAction
All Implemented Interfaces:
Serializable
Direct Known Subclasses:
EventDispatchAction, LookupDispatchAction, MappingDispatchAction
public abstract class DispatchAction extends BaseAction

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.extras.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.

Version:
$Rev$ $Date$
See Also:

  • Field Details

    • clazz

      protected Class<? extends DispatchAction> 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

    • DispatchAction

      public DispatchAction()

  • 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.
      Overrides:
      execute in class Action
      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
      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:
      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
      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.
      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.
      Since:
      Struts 1.2.0

    • 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.
      Since:
      Struts 1.1

    • getParameter

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

      Returns the parameter 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
      Returns:
      The ActionMapping parameter's value
      Throws:
      Exception - if the parameter is missing.

    • 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

    • 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.
      Since:
      Struts 1.2.0