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 */
017package org.apache.camel.impl;
018
019import java.io.IOException;
020
021import org.apache.camel.CamelContext;
022import org.apache.camel.Component;
023import org.apache.camel.NoFactoryAvailableException;
024import org.apache.camel.spi.ComponentResolver;
025import org.apache.camel.spi.FactoryFinder;
026import org.apache.camel.util.CamelContextHelper;
027import org.slf4j.Logger;
028import org.slf4j.LoggerFactory;
029
030/**
031 * The default implementation of {@link ComponentResolver} which tries to find
032 * components by using the URI scheme prefix and searching for a file of the URI
033 * scheme name in the <b>META-INF/services/org/apache/camel/component/</b>
034 * directory on the classpath.
035 *
036 * @version 
037 */
038public class DefaultComponentResolver implements ComponentResolver {
039
040    public static final String RESOURCE_PATH = "META-INF/services/org/apache/camel/component/";
041    private static final Logger LOG = LoggerFactory.getLogger(DefaultComponentResolver.class);
042    private FactoryFinder factoryFinder;
043
044    public Component resolveComponent(String name, CamelContext context) {
045        // lookup in registry first
046        Object bean = null;
047        try {
048            bean = context.getRegistry().lookupByName(name);
049            getLog().debug("Found component: {} in registry: {}", name, bean);
050        } catch (Exception e) {
051            getLog().debug("Ignored error looking up bean: " + name, e);
052        }
053        if (bean != null) {
054            if (bean instanceof Component) {
055                return (Component) bean;
056            } else {
057                // lets use Camel's type conversion mechanism to convert things like CamelContext
058                // and other types into a valid Component
059                Component component = CamelContextHelper.convertTo(context, Component.class, bean);
060                if (component != null) {
061                    return component;
062                }
063            }
064            // we do not throw the exception here and try to auto create a component
065        }
066
067        // not in registry then use component factory
068        Class<?> type;
069        try {
070            type = findComponent(name, context);
071            if (type == null) {
072                // not found
073                return null;
074            }
075        } catch (NoFactoryAvailableException e) {
076            return null;
077        } catch (Exception e) {
078            throw new IllegalArgumentException("Invalid URI, no Component registered for scheme: " + name, e);
079        }
080
081        if (getLog().isDebugEnabled()) {
082            getLog().debug("Found component: {} via type: {} via: {}{}", new Object[]{name, type.getName(), factoryFinder.getResourcePath(), name});
083        }
084
085        // create the component
086        if (Component.class.isAssignableFrom(type)) {
087            return (Component) context.getInjector().newInstance(type);
088        } else {
089            throw new IllegalArgumentException("Type is not a Component implementation. Found: " + type.getName());
090        }
091    }
092
093    private Class<?> findComponent(String name, CamelContext context) throws ClassNotFoundException, IOException {
094        if (factoryFinder == null) {
095            factoryFinder = context.getFactoryFinder(RESOURCE_PATH);
096        }
097        return factoryFinder.findClass(name);
098    }
099
100    protected Logger getLog() {
101        return LOG;
102    }
103
104}