org.apache.struts.actions
Class DispatchAction

java.lang.Object
  |
  +--org.apache.struts.action.Action
        |
        +--org.apache.struts.actions.DispatchAction

public abstract 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 "perform" method, which must have the same signature (other than method name) of the standard Action.perform() 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 IOException, ServletException
• public ActionForward insert(ActionMapping mapping, ActionForm form, HttpServletRequest request, HttpServletResponse response) throws IOException, ServletException
• public ActionForward update(ActionMapping mapping, ActionForm form, HttpServletRequest request, HttpServletResponse response) throws IOException, ServletException

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.

Version:

$Revision: 1.1 $ $Date: 2001/09/17 20:05:42 $

Author:

Niall Pemberton , Craig R. McClanahan

Field Summary

protected java.lang.Class	clazz The Class instance of this DispatchAction class.
protected static MessageResources	messages The message resources for this package.
protected java.util.HashMap	methods The set of Method objects we have introspected for this class, keyed by method name.
protected java.lang.Class[]	types The set of argument type classes for the reflected method call.

Fields inherited from class org.apache.struts.action.Action

DATA_SOURCE_KEY, defaultLocale, ERROR_KEY, EXCEPTION_KEY, FORM_BEANS_KEY, FORWARDS_KEY, LOCALE_KEY, MAPPING_KEY, MAPPINGS_KEY, MESSAGES_KEY, MULTIPART_KEY, servlet, SERVLET_KEY, TRANSACTION_TOKEN_KEY

Constructor Summary

DispatchAction()

Method Summary

protected java.lang.reflect.Method	getMethod(java.lang.String name) Introspect the current class to identify a method of the specified name that accepts the same parameter types as the perform() method does.
ActionForward	perform(ActionMapping mapping, ActionForm form, javax.servlet.http.HttpServletRequest request, javax.servlet.http.HttpServletResponse response) Process the specified HTTP request, and create the corresponding HTTP response (or forward to another web component that will create it).

Methods inherited from class org.apache.struts.action.Action

generateToken, getLocale, getResources, getServlet, isCancelled, isTokenValid, perform, perform, perform, resetToken, saveErrors, saveToken, setLocale, setServlet, toHex

Methods inherited from class java.lang.Object

, clone, equals, finalize, getClass, hashCode, notify, notifyAll, registerNatives, toString, wait, wait, wait

Field Detail

clazz

protected java.lang.Class clazz

The Class instance of this DispatchAction class.

messages

protected static MessageResources messages

The message resources for this package.

methods

protected java.util.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 java.lang.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

DispatchAction

public DispatchAction()

Method Detail

perform

public ActionForward perform(ActionMapping mapping,
                             ActionForm form,
                             javax.servlet.http.HttpServletRequest request,
                             javax.servlet.http.HttpServletResponse response)
                      throws java.io.IOException,
                             javax.servlet.ServletException

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:

perform in class Action

Parameters:

mapping - The ActionMapping used to select this instance

actionForm - The optional ActionForm bean for this request (if any)

request - The HTTP request we are processing

response - The HTTP response we are creating

Throws:

java.io.IOException - if an input/output error occurs

javax.servlet.ServletException - if a servlet exception occurs

getMethod

protected java.lang.reflect.Method getMethod(java.lang.String name)
                                      throws java.lang.NoSuchMethodException

Introspect the current class to identify a method of the specified name that accepts the same parameter types as the perform() method does.

Parameters:

name - Name of the method to be introspected

Throws:

java.lang.NoSuchMethodException - if no such method can be found