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 org.apache.camel.CamelContext;
020    import org.apache.camel.Component;
021    import org.apache.camel.Exchange;
022    import org.apache.camel.spi.ComponentResolver;
023    import org.apache.camel.util.FactoryFinder;
024    import org.apache.camel.util.NoFactoryAvailableException;
025    
026    /**
027     * The default implementation of {@link ComponentResolver} which tries to find
028     * components by using the URI scheme prefix and searching for a file of the URI
029     * scheme name in the <b>META-INF/services/org/apache/camel/component/</b>
030     * directory on the classpath.
031     * 
032     * @version $Revision: 563607 $
033     */
034    public class DefaultComponentResolver<E extends Exchange> implements ComponentResolver<E> {
035        protected static final FactoryFinder COMPONENT_FACTORY = 
036            new FactoryFinder("META-INF/services/org/apache/camel/component/");
037    
038        public Component<E> resolveComponent(String name, CamelContext context) {
039            Class type;
040            try {
041                type = COMPONENT_FACTORY.findClass(name);
042            } catch (NoFactoryAvailableException e) {
043                return null;
044            } catch (Throwable e) {
045                throw new IllegalArgumentException("Invalid URI, no Component registered for scheme : " 
046                                                   + name, e);
047            }
048            if (type == null) {
049                return null;
050            }
051            if (Component.class.isAssignableFrom(type)) {
052                return (Component<E>)context.getInjector().newInstance(type);
053            } else {
054                throw new IllegalArgumentException("Type is not a Component implementation. Found: "
055                                                   + type.getName());
056            }
057        }
058    }