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.component.bean;
018    
019    import java.lang.annotation.Annotation;
020    import java.lang.reflect.Method;
021    
022    import org.apache.camel.CamelContext;
023    import org.apache.camel.Expression;
024    import org.apache.camel.language.LanguageAnnotation;
025    import org.apache.camel.spi.Language;
026    import org.apache.camel.util.ObjectHelper;
027    
028    /**
029     * @version $Revision: 36321 $
030     */
031    public class DefaultAnnotationExpressionFactory implements AnnotationExpressionFactory {
032        public Expression createExpression(CamelContext camelContext, Annotation annotation, LanguageAnnotation languageAnnotation, Class expressionReturnType) {
033            String languageName = languageAnnotation.language();
034            if (languageName == null) {
035                throw new IllegalArgumentException("Cannot determine the language from the annotation: " + annotation);
036            }
037            Language language = camelContext.resolveLanguage(languageName);
038            if (language == null) {
039                throw new IllegalArgumentException("Cannot find the language: " + languageName + " on the classpath");
040            }
041            String expression = getExpressionFromAnnotation(annotation);
042            return language.createExpression(expression);
043        }
044    
045        protected String getExpressionFromAnnotation(Annotation annotation) {
046            // lets try the 'value()' method
047            try {
048                Method method = annotation.getClass().getMethod("value");
049                Object value = ObjectHelper.invokeMethod(method, annotation);
050                if (value == null) {
051                    throw new IllegalArgumentException("Cannot determine the expression from the annotation: " + annotation);
052                }
053                return value.toString();
054            } catch (NoSuchMethodException e) {
055                throw new IllegalArgumentException("Cannot determine the expression of the annotation: " + annotation + " as it does not have an value() method");
056            }
057        }
058    }