/*
* 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.action;
import org.springframework.binding.expression.Expression;
import org.springframework.core.style.ToStringCreator;
import org.springframework.util.Assert;
import org.springframework.webflow.execution.Action;
import org.springframework.webflow.execution.ActionExecutor;
import org.springframework.webflow.execution.Event;
import org.springframework.webflow.execution.RequestContext;
/**
* An action that evaluates an expression and optionally exposes its result.
* <p>
* Delegates to a {@link ResultEventFactory} to determine how to map the evaluation result to an action outcome
* {@link Event}.
*
* @see Expression
* @see ResultEventFactory
*
* @author Keith Donald
* @author Jeremy Grelle
*/
public class EvaluateAction extends AbstractAction {
/**
* The expression to evaluate when this action is invoked. Required.
*/
private Expression expression;
/**
* The expression to evaluate to set the result of the action. Optional.
*/
private Expression resultExpression;
/**
* The selector for the factory that will create the action result event callers can respond to.
*/
private ResultEventFactory resultEventFactory;
/**
* Create a new evaluate action.
* @param expression the expression to evaluate (required)
* @param resultExpression the expression to evaluate the result (optional)
*/
public EvaluateAction(Expression expression, Expression resultExpression) {
init(expression, resultExpression, null);
}
/**
* Create a new evaluate action.
* @param expression the expression to evaluate (required)
* @param resultExpression the strategy for how the expression result will be exposed to the flow (optional)
* @param resultEventFactory the factory that will map the evaluation result to a Web Flow event (optional)
*/
public EvaluateAction(Expression expression, Expression resultExpression, ResultEventFactory resultEventFactory) {
init(expression, resultExpression, resultEventFactory);
}
protected Event doExecute(RequestContext context) throws Exception {
Object result = expression.getValue(context);
if (result instanceof Action) {
return ActionExecutor.execute((Action) result, context);
} else {
if (resultExpression != null) {
resultExpression.setValue(context, result);
}
return resultEventFactory.createResultEvent(this, result, context);
}
}
public String toString() {
return new ToStringCreator(this).append("expression", expression).append("resultExpression", resultExpression)
.toString();
}
// internal helpers
private void init(Expression expression, Expression resultExpression, ResultEventFactory resultEventFactory) {
Assert.notNull(expression, "The expression this action should evaluate is required");
this.expression = expression;
this.resultExpression = resultExpression;
this.resultEventFactory = resultEventFactory != null ? resultEventFactory : new DefaultResultEventFactory();
}
/**
* Default implementation that uses the ResultEventFactorySelector helper.
* @author Keith Donald
*/
private class DefaultResultEventFactory implements ResultEventFactory {
private ResultEventFactorySelector selector = new ResultEventFactorySelector();
public Event createResultEvent(Object source, Object resultObject, RequestContext context) {
return selector.forResult(resultObject).createResultEvent(source, resultObject, context);
}
}
}