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.impl;
018    
019    import java.io.IOException;
020    
021    import org.apache.camel.CamelContext;
022    import org.apache.camel.NoSuchLanguageException;
023    import org.apache.camel.spi.Language;
024    import org.apache.camel.spi.LanguageResolver;
025    import org.apache.camel.util.FactoryFinder;
026    import org.apache.camel.util.NoFactoryAvailableException;
027    import org.apache.commons.logging.Log;
028    import org.apache.commons.logging.LogFactory;
029    
030    
031    /**
032     * Default language resolver that looks for language factories in <b>META-INF/services/org/apache/camel/language/</b> and
033     * language resolvers in <b>META-INF/services/org/apache/camel/language/resolver/</b>.
034     *
035     * @version $Revision: 752787 $
036     */
037    public class DefaultLanguageResolver implements LanguageResolver {    
038        protected static final FactoryFinder LANGUAGE_FACTORY = new FactoryFinder("META-INF/services/org/apache/camel/language/");
039        protected static final FactoryFinder LANGUAGE_RESOLVER = new FactoryFinder("META-INF/services/org/apache/camel/language/resolver/");
040        private static final transient Log LOG = LogFactory.getLog(DefaultLanguageResolver.class);
041        
042        protected Log getLog() {
043            return LOG;
044        }
045        public Language resolveLanguage(String name, CamelContext context) {
046            Object bean = null;
047            try {
048                bean = context.getRegistry().lookup(name);
049                if (bean != null && getLog().isDebugEnabled()) {
050                    getLog().debug("Found language: " + name + " in registry: " + bean);
051                }
052            } catch (Exception e) {
053                getLog().debug("Ignored error looking up bean: " + name + ". Error: " + e);
054            }
055            if (bean != null) {
056                if (bean instanceof Language) {
057                    return (Language)bean;
058                }
059                // we do not throw the exception here and try to auto create a Language from META-INF
060            }
061            Class type = null;
062            try {
063                type = findLanguage(name);
064            } catch (NoFactoryAvailableException e) {
065                // ignore
066            } catch (Throwable e) {
067                throw new IllegalArgumentException("Invalid URI, no Language registered for scheme : " + name, e);
068            }
069            if (type != null) {
070                if (Language.class.isAssignableFrom(type)) {
071                    return (Language)context.getInjector().newInstance(type);
072                } else {
073                    throw new IllegalArgumentException("Type is not a Language implementation. Found: " + type.getName());
074                }
075            }
076            return noSpecificLanguageFound(name, context);
077        }
078    
079        protected Language noSpecificLanguageFound(String name, CamelContext context) {
080            Class type = null;
081            try {
082                type = findLanguageResolver("default");
083            } catch (NoFactoryAvailableException e) {
084                // ignore
085            } catch (Throwable e) {
086                throw new IllegalArgumentException("Invalid URI, no Language registered for scheme : " + name, e);
087            }
088            if (type != null) {
089                if (LanguageResolver.class.isAssignableFrom(type)) {
090                    LanguageResolver resolver = (LanguageResolver)context.getInjector().newInstance(type);
091                    return resolver.resolveLanguage(name, context);
092                } else {
093                    throw new IllegalArgumentException("Type is not a LanguageResolver implementation. Found: " + type.getName());
094                }
095            }
096            throw new NoSuchLanguageException(name);
097        }
098        
099        protected Class findLanguage(String name) throws Exception {
100            return LANGUAGE_FACTORY.findClass(name);
101        }
102        
103        protected Class findLanguageResolver(String name) throws Exception {
104            return LANGUAGE_RESOLVER.findClass("default");
105        }
106    }