/*
 * 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.avalon.framework.service;

import org.apache.avalon.framework.component.Component;
import org.apache.avalon.framework.component.ComponentException;
import org.apache.avalon.framework.component.ComponentSelector;

This is a ServiceSelector implementation that can wrap around a legacy ComponentSelector object effectively adapting a ComponentSelector interface to a ServiceSelector interface. 
 This class implements the Component interface because it is used in environments which expect all components to implement Component. 
Author:
Avalon Development Team
Version:
$Id: WrapperServiceSelector.java 506231 2007-02-12 02:36:54Z crossley $
Since:
4.1.4/**
 * This is a {@link ServiceSelector} implementation that can wrap around a legacy
 * {@link ComponentSelector} object effectively adapting a {@link ComponentSelector}
 * interface to a {@link ServiceSelector} interface.
 * <p>
 * This class implements the {@link Component} interface because it is used in
 * environments which expect all components to implement Component.
 *
 * @author <a href="mailto:dev@avalon.apache.org">Avalon Development Team</a>
 * @version $Id: WrapperServiceSelector.java 506231 2007-02-12 02:36:54Z crossley $
 * @since 4.1.4
 */
public class WrapperServiceSelector
    implements ServiceSelector
{
    
The Selector we are wrapping.
/**
     * The Selector we are wrapping.
     */
    private final ComponentSelector m_selector;

    
The role that this selector was aquired via.
/**
     * The role that this selector was aquired via.
     */
    private final String m_key;

    
This constructor is a constructor for a ComponentServiceManager
Params:
key – the key used to aquire this selector
selector – the selector to wrap/**
     * This constructor is a constructor for a ComponentServiceManager
     *
     * @param key the key used to aquire this selector
     * @param selector the selector to wrap
     */
    public WrapperServiceSelector( final String key,
                                   final ComponentSelector selector )
    {
        if( null == key )
        {
            throw new NullPointerException( "key" );
        }
        if( null == selector )
        {
            throw new NullPointerException( "selector" );
        }

        m_key = key + "/";
        m_selector = selector;
    }

    
Select a service based on a policy.
Params:
policy – the policy
Throws:
ServiceException – if unable to select service
Returns:
the service/**
     * Select a service based on a policy.
     *
     * @param policy the policy
     * @return the service
     * @throws ServiceException if unable to select service
     */
    public Object select( final Object policy )
        throws ServiceException
    {
        try
        {
            return m_selector.select( policy );
        }
        catch( final ComponentException ce )
        {
            throw new ServiceException( m_key + policy, ce.getMessage(), ce );
        }
    }

    
Check to see if a Object exists relative to the supplied policy. 
Params:
policy – a Object containing the selection criteria
Returns:
True if the component is available, False if it not./**
     * Check to see if a {@link Object} exists relative to the supplied policy.
     *
     * @param policy a {@link Object} containing the selection criteria
     * @return True if the component is available, False if it not.
     */
    public boolean isSelectable( final Object policy )
    {
        return m_selector.hasComponent( policy );
    }

    
Return the Object when you are finished with it. This allows the ServiceSelector to handle the End-Of-Life Lifecycle events associated with the Object. Please note, that no Exception should be thrown at this point. This is to allow easy use of the ServiceSelector system without having to trap Exceptions on a release. 
Params:
object – The Object we are releasing./**
     * Return the {@link Object} when you are finished with it.  This
     * allows the {@link ServiceSelector} to handle the End-Of-Life Lifecycle
     * events associated with the {@link Object}.  Please note, that no
     * Exception should be thrown at this point.  This is to allow easy use of the
     * ServiceSelector system without having to trap Exceptions on a release.
     *
     * @param object The {@link Object} we are releasing.
     */
    public void release( Object object )
    {
        m_selector.release( (Component)object );
    }

    
The WrapperServiceManager wraps ComponentSelectors in WrapperServiceSelectors when they are looked up. This method makes it possible to release the original component selector. 
Returns:
The ComponentSelector being wrapped./**
     * The {@link WrapperServiceManager} wraps ComponentSelectors in
     *  WrapperServiceSelectors when they are looked up.  This method
     *  makes it possible to release the original component selector.
     *
     * @return The {@link ComponentSelector} being wrapped.
     */
    ComponentSelector getWrappedSelector()
    {
        return m_selector;
    }
}