org.springframework.webflow.action.EvaluateAction Maven / Gradle / Ivy
/*
* Copyright 2004-2007 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.EvaluationContext;
import org.springframework.binding.expression.Expression;
import org.springframework.util.Assert;
import org.springframework.webflow.execution.Event;
import org.springframework.webflow.execution.RequestContext;
/**
* An action that evaluates an expression and optionally exposes its result.
*
* Delegates to a helper {@link ResultEventFactorySelector} strategy to determine how to map the evaluation result to an
* action outcome {@link Event}.
*
* @see Expression
* @see ActionResultExposer
* @see ResultEventFactorySelector
*
* @author Keith Donald
*/
public class EvaluateAction extends AbstractAction {
/**
* The expression to evaluate when this action is invoked. Required.
*/
private Expression expression;
/**
* The helper that will expose the expression evaluation result. Optional.
*/
private ActionResultExposer evaluationResultExposer;
/**
* The selector for the factory that will create the action result event callers can respond to.
*/
private ResultEventFactorySelector resultEventFactorySelector = new ResultEventFactorySelector();
/**
* Create a new evaluate action.
* @param expression the expression to evaluate
*/
public EvaluateAction(Expression expression) {
this(expression, null);
}
/**
* Create a new evaluate action.
* @param expression the expression to evaluate
* @param evaluationResultExposer the strategy for how the expression result will be exposed to the flow
*/
public EvaluateAction(Expression expression, ActionResultExposer evaluationResultExposer) {
Assert.notNull(expression, "The expression this action should evaluate is required");
this.expression = expression;
this.evaluationResultExposer = evaluationResultExposer;
}
protected Event doExecute(RequestContext context) throws Exception {
Object result = expression.evaluate(context, getEvaluationContext(context));
if (evaluationResultExposer != null) {
evaluationResultExposer.exposeResult(result, context);
}
return resultEventFactorySelector.forResult(result).createResultEvent(this, result, context);
}
/**
* Template method subclasses may override to customize the expressin evaluation context. This implementation
* returns null.
* @param context the request context
* @return the evaluation context
*/
protected EvaluationContext getEvaluationContext(RequestContext context) {
return null;
}
}