/*
* 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.builder.support;
import org.springframework.binding.convert.ConversionExecutionException;
import org.springframework.binding.convert.converters.Converter;
import org.springframework.binding.expression.Expression;
import org.springframework.binding.expression.ExpressionParser;
import org.springframework.binding.expression.support.FluentParserContext;
import org.springframework.util.StringUtils;
import org.springframework.webflow.engine.TransitionCriteria;
import org.springframework.webflow.engine.WildcardTransitionCriteria;
import org.springframework.webflow.engine.builder.FlowBuilderContext;
import org.springframework.webflow.engine.support.DefaultTransitionCriteria;
import org.springframework.webflow.execution.RequestContext;
/**
* Converter that takes an encoded string representation and produces a corresponding <code>TransitionCriteria</code>
* object.
* <p>
* This converter supports the following encoded forms:
* <ul>
* <li>"*" - will result in a TransitionCriteria object that matches on everything.</li>
* <li>"eventId" - will result in a TransitionCriteria object that matches given event id.</li>
* <li>"${...}" - will result in a TransitionCriteria object that evaluates given condition, expressed as an expression.
* </li>
* </ul>
*
* @see org.springframework.webflow.engine.TransitionCriteria
*
* @author Keith Donald
* @author Erwin Vervaet
*/
class TextToTransitionCriteria implements Converter {
/**
* Context for flow builder services.
*/
private FlowBuilderContext flowBuilderContext;
/**
* Create a new converter that converts strings to transition criteria objects. Custom transition criteria will be
* looked up using given service locator.
*/
public TextToTransitionCriteria(FlowBuilderContext flowBuilderContext) {
this.flowBuilderContext = flowBuilderContext;
}
public Class<?> getSourceClass() {
return String.class;
}
public Class<?> getTargetClass() {
return TransitionCriteria.class;
}
public Object convertSourceToTargetClass(Object source, Class<?> targetClass) throws Exception {
String encodedCriteria = (String) source;
ExpressionParser parser = flowBuilderContext.getExpressionParser();
if (!StringUtils.hasText(encodedCriteria)
|| WildcardTransitionCriteria.WILDCARD_EVENT_ID.equals(encodedCriteria)) {
return WildcardTransitionCriteria.INSTANCE;
} else {
return createBooleanExpressionTransitionCriteria(encodedCriteria, parser);
}
}
/**
* Hook method subclasses can override to return a specialized expression evaluating transition criteria
* implementation.
* @param encodedCriteria the encoded transition criteria expression
* @param parser the parser that should parse the expression
* @return the transition criteria object
* @throws ConversionExecutionException when something goes wrong
*/
protected TransitionCriteria createBooleanExpressionTransitionCriteria(String encodedCriteria,
ExpressionParser parser) throws ConversionExecutionException {
Expression expression = parser.parseExpression(encodedCriteria,
new FluentParserContext().template().evaluate(RequestContext.class));
return new DefaultTransitionCriteria(expression);
}
}