/*
* Copyright 2014-2016 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.integration.routingslip;
import org.springframework.beans.BeansException;
import org.springframework.beans.factory.BeanFactory;
import org.springframework.beans.factory.BeanFactoryAware;
import org.springframework.beans.factory.InitializingBean;
import org.springframework.expression.EvaluationContext;
import org.springframework.expression.Expression;
import org.springframework.expression.ExpressionParser;
import org.springframework.expression.spel.standard.SpelExpressionParser;
import org.springframework.integration.expression.ExpressionUtils;
import org.springframework.messaging.Message;
/**
* The {@link Expression} based {@link RoutingSlipRouteStrategy} implementation.
* The {@code requestMessage} and {@code reply} object are wrapped
* to the {@link RequestAndReply} which is used as a {@link EvaluationContext} {@code rootObject}.
* This is necessary to avoid a creation of a new {@link EvaluationContext} on each invocation
* when additional parameter can be populated as expression variable, but {@link EvaluationContext}
* isn't thread-safe.
* <p>
* The {@link ExpressionEvaluatingRoutingSlipRouteStrategy} can be used directly as a regular bean
* in the {@code ApplicationContext} and its {@code beanName} can be used from {@code routingSlip}
* header configuration.
* <p>
* Usage of {@link ExpressionEvaluatingRoutingSlipRouteStrategy} as a regular bean definition is
* a recommended way in case of distributed environment, when message with {@code routingSlip}
* header can be sent across the network. One of this case is a {@code QueueChannel} with
* persistent {@code MessageStore}, when {@link ExpressionEvaluatingRoutingSlipRouteStrategy}
* instance as a header value will be non-serializable.
* <p>
* This class is used internally from {@code RoutingSlipHeaderValueMessageProcessor}
* to populate {@code routingSlip} header value item, when the {@code value}
* from configuration contains expression definitions:
* <pre class="code">
* {@code
* <header-enricher>
* <routing-slip
* value="channel1; @routingSlipPojo.get(request, reply); request.headers[foo]"/>
* </header-enricher>
* }
* </pre>
*
* @author Artem Bilan
* @author Gary Russell
* @since 4.1
*/
public class ExpressionEvaluatingRoutingSlipRouteStrategy
implements RoutingSlipRouteStrategy, BeanFactoryAware, InitializingBean {
private static final ExpressionParser PARSER = new SpelExpressionParser();
private final Expression expression;
private EvaluationContext evaluationContext;
private BeanFactory beanFactory;
public ExpressionEvaluatingRoutingSlipRouteStrategy(String expression) {
this(PARSER.parseExpression(expression));
}
public ExpressionEvaluatingRoutingSlipRouteStrategy(Expression expression) {
this.expression = expression;
}
public void setIntegrationEvaluationContext(EvaluationContext evaluationContext) {
this.evaluationContext = evaluationContext;
}
@Override
public void setBeanFactory(BeanFactory beanFactory) throws BeansException {
this.beanFactory = beanFactory;
}
@Override
public void afterPropertiesSet() throws Exception {
if (this.evaluationContext == null) {
this.evaluationContext = ExpressionUtils.createStandardEvaluationContext(this.beanFactory);
}
}
@Override
public Object getNextPath(Message<?> requestMessage, Object reply) {
return this.expression.getValue(this.evaluationContext, new RequestAndReply(requestMessage, reply),
String.class);
}
@Override
public String toString() {
return "ExpressionEvaluatingRoutingSlipRouteStrategy for: [" + this.expression.getExpressionString() + "]";
}
public static class RequestAndReply {
private final Message<?> request;
private final Object reply;
RequestAndReply(Message<?> request, Object reply) {
this.request = request;
this.reply = reply;
}
public Message<?> getRequest() {
return this.request;
}
public Object getReply() {
return this.reply;
}
}
}