001 /**
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements. See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to You under the Apache License, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License. You may obtain a copy of the License at
008 *
009 * http://www.apache.org/licenses/LICENSE-2.0
010 *
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the License for the specific language governing permissions and
015 * limitations under the License.
016 */
017 package org.apache.camel.language.juel;
018
019 import java.util.Properties;
020
021 import javax.el.ArrayELResolver;
022 import javax.el.CompositeELResolver;
023 import javax.el.ELContext;
024 import javax.el.ELResolver;
025 import javax.el.ExpressionFactory;
026 import javax.el.ListELResolver;
027 import javax.el.MapELResolver;
028 import javax.el.ResourceBundleELResolver;
029 import javax.el.ValueExpression;
030 import de.odysseus.el.util.SimpleContext;
031 import org.apache.camel.Exchange;
032 import org.apache.camel.Message;
033 import org.apache.camel.impl.ExpressionSupport;
034
035 /**
036 * The <a href="http://camel.apache.org/el.html">EL Language from JSP and JSF</a>
037 * using the <a href="http://camel.apache.org/juel.html">JUEL library</a>
038 *
039 * @version $Revision: 769448 $
040 */
041 public class JuelExpression extends ExpressionSupport {
042 private final String expression;
043 private final Class<?> type;
044 private ExpressionFactory expressionFactory;
045 private Properties expressionFactoryProperties;
046
047 public JuelExpression(String expression, Class<?> type) {
048 this.expression = expression;
049 this.type = type;
050 }
051
052 public static JuelExpression el(String expression) {
053 return new JuelExpression(expression, Object.class);
054 }
055
056 public <T> T evaluate(Exchange exchange, Class<T> tClass) {
057 // TODO we could use caching here but then we'd have possible concurrency issues
058 // so lets assume that the provider caches
059 ELContext context = populateContext(createContext(), exchange);
060 ValueExpression valueExpression = getExpressionFactory().createValueExpression(context, expression, type);
061 Object value = valueExpression.getValue(context);
062 return exchange.getContext().getTypeConverter().convertTo(tClass, value);
063 }
064
065 public ExpressionFactory getExpressionFactory() {
066 if (expressionFactory == null) {
067 Properties properties = getExpressionFactoryProperties();
068 expressionFactory = ExpressionFactory.newInstance(properties);
069 }
070 return expressionFactory;
071 }
072
073 public void setExpressionFactory(ExpressionFactory expressionFactory) {
074 this.expressionFactory = expressionFactory;
075 }
076
077 public Properties getExpressionFactoryProperties() {
078 if (expressionFactoryProperties == null) {
079 expressionFactoryProperties = new Properties();
080 populateDefaultExpressionProperties(expressionFactoryProperties);
081 }
082 return expressionFactoryProperties;
083 }
084
085 public void setExpressionFactoryProperties(Properties expressionFactoryProperties) {
086 this.expressionFactoryProperties = expressionFactoryProperties;
087 }
088
089 protected ELContext populateContext(ELContext context, Exchange exchange) {
090 setVariable(context, "exchange", exchange, Exchange.class);
091 setVariable(context, "in", exchange.getIn(), Message.class);
092 if (exchange.hasOut()) {
093 setVariable(context, "out", exchange.getOut(), Message.class);
094 }
095 return context;
096 }
097
098 /**
099 * A Strategy Method to populate the default properties used to create the expression factory
100 */
101 protected void populateDefaultExpressionProperties(Properties properties) {
102 // lets enable method invocations
103 properties.setProperty("javax.el.methodInvocations", "true");
104 }
105
106 protected void setVariable(ELContext context, String name, Object value, Class<?> type) {
107 ValueExpression valueExpression = getExpressionFactory().createValueExpression(value, type);
108 SimpleContext simpleContext = (SimpleContext) context;
109 simpleContext.setVariable(name, valueExpression);
110 }
111
112 /**
113 * Factory method to create the EL context
114 */
115 protected ELContext createContext() {
116 ELResolver resolver = new CompositeELResolver() {
117 {
118 //add(methodResolver);
119 add(new ArrayELResolver(false));
120 add(new ListELResolver(false));
121 add(new MapELResolver(false));
122 add(new ResourceBundleELResolver());
123 add(new BeanAndMethodELResolver());
124 }
125 };
126 return new SimpleContext(resolver);
127 }
128
129 protected String assertionFailureMessage(Exchange exchange) {
130 return expression;
131 }
132 }