ActionState.java
/*
* 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
*
* https://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.
* <p>
* 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.
* <p>
* 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. <p>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 <code>doEnter</code> template method that executes behavior specific to this state type
* in polymorphic fashion.
* <p>
* This implementation iterates over each configured <code>Action</code> instance and executes it. Execution
* continues until an <code>Action</code> 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<Action> 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...");
}
}
}