package org.codehaus.plexus.component.discovery;
   
   /*
    * Copyright 2001-2006 Codehaus Foundation.
    *
    * Licensed under the Apache License, Version 2.0 (the "License");
    * you may not use this file except in compliance with the License.
    * You may obtain a copy of the License at
    *
   *      http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  
  import java.io.Reader;
  import java.util.ArrayList;
  import java.util.List;
  
  import org.codehaus.plexus.classworlds.realm.ClassRealm;
  import org.codehaus.plexus.component.repository.ComponentDescriptor;
  import org.codehaus.plexus.component.repository.ComponentSetDescriptor;
  import org.codehaus.plexus.component.repository.io.PlexusTools;
  import org.codehaus.plexus.configuration.PlexusConfiguration;
  import org.codehaus.plexus.configuration.PlexusConfigurationException;
  
  /**
   * @author Jason van Zyl
   */
  public class DefaultComponentDiscoverer extends AbstractResourceBasedComponentDiscoverer {
      public String getComponentDescriptorLocation() {
          return "META-INF/plexus/components.xml";
      }
  
      public ComponentSetDescriptor createComponentDescriptors(
              Reader componentDescriptorReader, String source, ClassRealm realm) throws PlexusConfigurationException {
          PlexusConfiguration componentDescriptorConfiguration =
                  PlexusTools.buildConfiguration(source, componentDescriptorReader);
  
          ComponentSetDescriptor componentSetDescriptor = new ComponentSetDescriptor();
  
          List<ComponentDescriptor<?>> componentDescriptors = new ArrayList<ComponentDescriptor<?>>();
  
          PlexusConfiguration[] componentConfigurations =
                  componentDescriptorConfiguration.getChild("components").getChildren("component");
  
          for (PlexusConfiguration componentConfiguration : componentConfigurations) {
              ComponentDescriptor<?> componentDescriptor;
              try {
                  componentDescriptor = PlexusTools.buildComponentDescriptor(componentConfiguration, realm);
              } catch (PlexusConfigurationException e) {
                  // This is not the most accurate of exceptions as the only real case where this exception
                  // will be thrown is when the implementation class of the component sited cannot be loaded.
                  // In the case where role and implementation classes do not exist then we just shouldn't
                  // create the component descriptor. All information should be taken from annotations which
                  // will be correct, so in the case we can't load the class it must be coming from and older
                  // hand written descriptor which is incorrect.
  
                  continue;
              }
  
              componentDescriptor.setSource(source);
  
              componentDescriptor.setComponentType("plexus");
  
              componentDescriptor.setComponentSetDescriptor(componentSetDescriptor);
  
              componentDescriptors.add(componentDescriptor);
          }
  
          componentSetDescriptor.setComponents(componentDescriptors);
  
          componentSetDescriptor.setSource(source);
  
          return componentSetDescriptor;
      }
  }