/**
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You 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.apache.camel.language.juel;
import java.io.IOException;
import java.util.Properties;
import javax.el.ArrayELResolver;
import javax.el.CompositeELResolver;
import javax.el.ELContext;
import javax.el.ELResolver;
import javax.el.ExpressionFactory;
import javax.el.ListELResolver;
import javax.el.MapELResolver;
import javax.el.ResourceBundleELResolver;
import javax.el.ValueExpression;
import de.odysseus.el.ExpressionFactoryImpl;
import de.odysseus.el.util.SimpleContext;
import org.apache.camel.CamelContext;
import org.apache.camel.Exchange;
import org.apache.camel.Message;
import org.apache.camel.impl.ExpressionSupport;
import org.apache.camel.spi.FactoryFinder;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
/**
* The <a href="http://camel.apache.org/el.html">EL Language from JSP and JSF</a>
* using the <a href="http://camel.apache.org/juel.html">JUEL library</a>
*
* @version
*/
public class JuelExpression extends ExpressionSupport {
public static final String DEFAULT_EXPRESSION_FACTORY_IMPL_CLASS = "de.odysseus.el.ExpressionFactoryImpl";
private static final Logger LOG = LoggerFactory.getLogger(JuelExpression.class);
private final String expression;
private final Class<?> type;
private ExpressionFactory expressionFactory;
public JuelExpression(String expression, Class<?> type) {
this.expression = expression;
this.type = type;
}
public static JuelExpression el(String expression) {
return new JuelExpression(expression, Object.class);
}
public <T> T evaluate(Exchange exchange, Class<T> tClass) {
// TODO we could use caching here but then we'd have possible concurrency issues
// so lets assume that the provider caches
// Create (if needed) the ExpressionFactory first from the CamelContext using FactoryFinder
ExpressionFactory factory = getExpressionFactory(exchange.getContext());
ELContext context = populateContext(createContext(), exchange);
ValueExpression valueExpression = factory.createValueExpression(context, expression, type);
Object value = valueExpression.getValue(context);
return exchange.getContext().getTypeConverter().convertTo(tClass, value);
}
public ExpressionFactory getExpressionFactory(CamelContext context) {
if (expressionFactory == null && context != null) {
try {
FactoryFinder finder = context.getFactoryFinder("META-INF/services/org/apache/camel/language/");
Class<?> clazz = finder.findClass("el", "impl.");
if (clazz != null) {
expressionFactory = (ExpressionFactory)clazz.newInstance();
}
} catch (ClassNotFoundException e) {
LOG.debug("'impl.class' not found", e);
} catch (IOException e) {
LOG.debug("No impl class for juel ExpressionFactory defined in 'META-INF/services/org/apache/camel/language/el'", e);
} catch (InstantiationException e) {
LOG.debug("Failed to instantiate juel ExpressionFactory implementation class.", e);
} catch (IllegalAccessException e) {
LOG.debug("Failed to instantiate juel ExpressionFactory implementation class.", e);
}
}
return getExpressionFactory();
}
public ExpressionFactory getExpressionFactory() {
if (expressionFactory == null) {
expressionFactory = new ExpressionFactoryImpl();
}
return expressionFactory;
}
public void setExpressionFactory(ExpressionFactory expressionFactory) {
this.expressionFactory = expressionFactory;
}
protected ELContext populateContext(ELContext context, Exchange exchange) {
setVariable(context, "exchange", exchange, Exchange.class);
setVariable(context, "in", exchange.getIn(), Message.class);
if (exchange.hasOut()) {
setVariable(context, "out", exchange.getOut(), Message.class);
}
return context;
}
protected void setVariable(ELContext context, String name, Object value, Class<?> type) {
ValueExpression valueExpression = getExpressionFactory().createValueExpression(value, type);
SimpleContext simpleContext = (SimpleContext) context;
simpleContext.setVariable(name, valueExpression);
}
/**
* Factory method to create the EL context
*/
protected ELContext createContext() {
ELResolver resolver = new CompositeELResolver() {
{
//add(methodResolver);
add(new ArrayELResolver(false));
add(new ListELResolver(false));
add(new MapELResolver(false));
add(new ResourceBundleELResolver());
add(new BeanAndMethodELResolver());
}
};
return new SimpleContext(resolver);
}
protected String assertionFailureMessage(Exchange exchange) {
return expression;
}
}