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/*
 * Copyright 2004-2012 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.springframework.webflow.engine;

import java.util.Iterator;

import org.springframework.core.style.StylerUtils;
import org.springframework.core.style.ToStringCreator;
import org.springframework.webflow.execution.Action;
import org.springframework.webflow.execution.ActionExecutor;
import org.springframework.webflow.execution.Event;
import org.springframework.webflow.execution.FlowExecutionException;
import org.springframework.webflow.execution.RequestContext;

/**
 * A transitionable state that executes one or more actions when entered. When the action(s) are executed this state
 * responds to their result(s) to decide what state to transition to next.
 * 

* If more than one action is configured they are executed in an ordered chain until one returns a result event that * matches a state transition out of this state. This is a form of the Chain of Responsibility (CoR) pattern. *

* The result of an action's execution is typically the criteria for a transition out of this state. Additional * information in the current {@link RequestContext} may also be tested as part of custom transitional criteria, * allowing for sophisticated transition expressions that reason on contextual state. * * @see org.springframework.webflow.execution.Action * * @author Keith Donald * @author Erwin Vervaet */ public class ActionState extends TransitionableState { /** * The list of actions to be executed when this state is entered. */ private ActionList actionList = new ActionList(); /** * Creates a new action state. * @param flow the owning flow * @param id the state identifier (must be unique to the flow) * @throws IllegalArgumentException when this state cannot be added to given flow, e.g. beasue the id is not unique * @see #getActionList() */ public ActionState(Flow flow, String id) throws IllegalArgumentException { super(flow, id); } /** * Returns the list of actions executable by this action state. The returned list is mutable. * @return the state action list */ public ActionList getActionList() { return actionList; } /* * Overrides getRequiredTransition(RequestContext) to throw a local NoMatchingActionResultTransitionException if a * transition on the occurrence of an action result event cannot be matched. Used to facilitate an action invocation * chain.

Note that we cannot catch NoMatchingTransitionException since that could lead to unwanted situations * where we're catching an exception that's generated by another state, e.g. because of a configuration error! */ public Transition getRequiredTransition(RequestContext context) throws NoMatchingTransitionException { Transition transition = getTransitionSet().getTransition(context); if (transition == null) { throw new NoMatchingActionResultTransitionException(this, context.getCurrentEvent()); } return transition; } /** * Specialization of State's doEnter template method that executes behavior specific to this state type * in polymorphic fashion. *

* This implementation iterates over each configured Action instance and executes it. Execution * continues until an Action returns a result event that matches a transition in this request context, * or the set of all actions is exhausted. * @param context the control context for the currently executing flow, used by this state to manipulate the flow * execution * @throws FlowExecutionException if an exception occurs in this state */ protected void doEnter(RequestControlContext context) throws FlowExecutionException { int executionCount = 0; String[] eventIds = new String[actionList.size()]; Iterator it = actionList.iterator(); while (it.hasNext()) { Action action = it.next(); Event event = ActionExecutor.execute(action, context); if (event != null) { eventIds[executionCount] = event.getId(); try { context.handleEvent(event); return; } catch (NoMatchingActionResultTransitionException e) { if (logger.isDebugEnabled()) { logger.debug("Action execution [" + (executionCount + 1) + "] resulted in no matching transition on event '" + event.getId() + "'" + (it.hasNext() ? ": proceeding to the next action in the list" : ": action list exhausted")); } } } else { if (logger.isDebugEnabled()) { logger.debug("Action execution [" + (executionCount + 1) + "] returned a [null] event" + (it.hasNext() ? ": proceeding to the next action in the list" : ": action list exhausted")); } eventIds[executionCount] = null; } executionCount++; } if (executionCount > 0) { throw new NoMatchingTransitionException(getFlow().getId(), getId(), context.getCurrentEvent(), "No transition was matched on the event(s) signaled by the [" + executionCount + "] action(s) that executed in this action state '" + getId() + "' of flow '" + getFlow().getId() + "'; transitions must be defined to handle action result outcomes -- " + "possible flow configuration error? Note: the eventIds signaled were: '" + StylerUtils.style(eventIds) + "', while the supported set of transitional criteria for this action state is '" + StylerUtils.style(getTransitionSet().getTransitionCriterias()) + "'"); } else { throw new IllegalStateException( "No actions were executed, thus I cannot execute any state transition " + "-- programmer configuration error; make sure you add at least one action to this state's action list"); } } protected void appendToString(ToStringCreator creator) { creator.append("actionList", actionList); super.appendToString(creator); } /** * Local "no transition found" exception used to report that an action result could not be mapped to a state * transition. * @author Keith Donald * @author Erwin Vervaet */ private static class NoMatchingActionResultTransitionException extends NoMatchingTransitionException { /** * Creates a new exception. * @param state the action state * @param resultEvent the action result event */ public NoMatchingActionResultTransitionException(ActionState state, Event resultEvent) { super(state.getFlow().getId(), state.getId(), resultEvent, "Cannot find a transition matching an action result event; continuing with next action..."); } } }





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