non-releases/cocoon-2_before-tagbase-experiment/core/cocoon-core/src/main/java/org/apache/cocoon/components/treeprocessor/NodeBuilderSelector.java

/* 
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You 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.
 */
package org.apache.cocoon.components.treeprocessor;

import java.util.Collections;
import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;

import org.apache.avalon.framework.activity.Initializable;
import org.apache.avalon.framework.configuration.Configurable;
import org.apache.avalon.framework.configuration.Configuration;
import org.apache.avalon.framework.configuration.ConfigurationException;
import org.apache.avalon.framework.container.ContainerUtil;
import org.apache.avalon.framework.context.Context;
import org.apache.avalon.framework.context.Contextualizable;
import org.apache.avalon.framework.logger.AbstractLogEnabled;
import org.apache.avalon.framework.parameters.Parameterizable;
import org.apache.avalon.framework.parameters.Parameters;
import org.apache.avalon.framework.service.ServiceException;
import org.apache.avalon.framework.service.ServiceManager;
import org.apache.avalon.framework.service.Serviceable;
import org.apache.avalon.framework.thread.ThreadSafe;

/**
 * This is the selector used to select/create node builders.
 *
 * @version $Id$
 * @since 2.2
 */
public class NodeBuilderSelector
    extends AbstractLogEnabled
    implements Serviceable,
               Configurable,
               Initializable,
               Contextualizable {

    /** The application context for components
     */
    protected ServiceManager serviceManager;

    /** The application context for components */
    protected Context context;

    /** Used to map roles to component infos. */
    protected final Map componentInfos = Collections.synchronizedMap(new HashMap());

    /** All singletons. */
    protected final Map singletons = Collections.synchronizedMap(new HashMap());

    /**
     * @see org.apache.avalon.framework.context.Contextualizable#contextualize(org.apache.avalon.framework.context.Context)
     */
    public void contextualize( final Context avalonContext ) {
        this.context = avalonContext;
    }

    /**
     * @see org.apache.avalon.framework.service.Serviceable#service(org.apache.avalon.framework.service.ServiceManager)
     */
    public void service( final ServiceManager componentManager )
    throws ServiceException {
        this.serviceManager = componentManager;
    }

    public Object getBuilder( String name )
    throws Exception {
        Object component = this.singletons.get(name);
        if ( component == null ) {
            final BuilderInfo info = (BuilderInfo)this.componentInfos.get( name );

            // Retrieve the instance of the requested component
            if( null == info ) {
                throw new Exception( "Node builder selector could not find builder for key [" + name + "]" );
            }
            try {
                component = this.createComponent(info);
            } catch (Exception e) {
                throw new Exception("Unable to create new builder: " + name, e);
            }
        }

        return component;
    }

    /**
     * @see org.apache.avalon.framework.configuration.Configurable#configure(org.apache.avalon.framework.configuration.Configuration)
     */
    public void configure( final Configuration config )
    throws ConfigurationException {
        final Configuration[] instances = config.getChildren();
        for (int i = 0; i < instances.length; i++) {
            final Configuration instance = instances[i];
            final String name = instance.getAttribute("name").trim();
            final String className = instance.getAttribute("builder").trim();
            try {
                if( this.getLogger().isDebugEnabled() ) {
                    this.getLogger().debug( "Adding builder (" + name + " = " + className + ")" );
                }

                final Class clazz = this.getClass().getClassLoader().loadClass( className );

                final BuilderInfo info = new BuilderInfo();
                info.builderClass = clazz;
                info.configuration = instance;

                this.componentInfos.put( name, info );

            } catch( final ClassNotFoundException cnfe ) {
                final String message = "Could not get class (" + className + ") for builder "
                                     + name + " at " + instance.getLocation();

                throw new ConfigurationException( message, cnfe );
            } catch( final Exception e ) {
                final String message = "Unexpected exception when setting up builder " + name + " at " + instance.getLocation();
                throw new ConfigurationException( message, e );
            }        
        }
    }

    /**
     * Create a new component.
     */
    protected Object createComponent(BuilderInfo info)
    throws Exception {
        final Object component = info.builderClass.newInstance();
        ContainerUtil.enableLogging(component, this.getLogger());
        ContainerUtil.contextualize(component, this.context);
        ContainerUtil.service(component, this.serviceManager);
        ContainerUtil.configure(component, info.configuration);
        if ( component instanceof Parameterizable ) {
            ContainerUtil.parameterize(component, Parameters.fromConfiguration(info.configuration));
        }
        ContainerUtil.initialize(component);
        return component;
    }

    /**
     * @see org.apache.avalon.framework.activity.Initializable#initialize()
     */
    public void initialize() 
    throws Exception {
        final Iterator i = this.componentInfos.entrySet().iterator();
        while ( i.hasNext() ) {
            final Map.Entry entry = (Map.Entry)i.next();
            final BuilderInfo info = (BuilderInfo)entry.getValue();
            if ( ThreadSafe.class.isAssignableFrom( info.builderClass ) ) {
                this.singletons.put(entry.getKey(), this.createComponent(info));
            }
        }
    }

    protected static class BuilderInfo {
        public Configuration configuration;
        public Class         builderClass;
    }
}