content: /*
   * Copyright (c) OSGi Alliance (2008, 2009). All Rights Reserved.
   *
   * 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.
   */
  package org.osgi.service.blueprint.reflect;
  
  import java.util.Collection;
  
  /**
   * Metadata for a reference to an OSGi service. This is the base type for
   * {@link ReferenceListMetadata} and {@link ReferenceMetadata}.
   * 
   * @ThreadSafe
   * @version $Revision$
   */
  public interface ServiceReferenceMetadata extends ComponentMetadata {
  
  	/**
  	 * A matching service is required at all times.
  	 * 
  	 * @see #getAvailability()
  	 */
  	static final int	AVAILABILITY_MANDATORY	= 1;
  
  	/**
  	 * A matching service is not required to be present.
  	 * 
  	 * @see #getAvailability()
  	 */
  	static final int	AVAILABILITY_OPTIONAL	= 2;
  
  	/**
  	 * Return whether or not a matching service is required at all times.
  	 * 
  	 * This is specified in the <code>availability</code> attribute of the
  	 * service reference.
  	 * 
  	 * @return Whether or not a matching service is required at all times.
  	 * @see #AVAILABILITY_MANDATORY
  	 * @see #AVAILABILITY_OPTIONAL
  	 */
  	int getAvailability();
  
  	/**
  	 * Return the name of the interface type that a matching service must
  	 * support.
  	 * 
  	 * This is specified in the <code>interface</code> attribute of the service
  	 * reference.
  	 * 
  	 * @return The name of the interface type that a matching service must
  	 *         support or <code>null</code> when no interface name is specified.
  	 */
  	String getInterface();
  
  	/**
  	 * Return the value of the <code>component-name</code> attribute of the
  	 * service reference. This specifies the id of a component that is
  	 * registered in the service registry. This will create an automatic filter,
  	 * appended with the filter if set, to select this component based on its
  	 * automatic <code>id</code> attribute.
  	 * 
  	 * @return The value of the <code>component-name</code> attribute of the
  	 *         service reference or <code>null</code> if the attribute is not
  	 *         specified.
  	 */
  	String getComponentName();
  
  	/**
  	 * Return the filter expression that a matching service must match.
  	 * 
  	 * This is specified by the <code>filter</code> attribute of the service
  	 * reference.
  	 * 
  	 * @return The filter expression that a matching service must match or
  	 *         <code>null</code> if a filter is not specified.
  	 */
  	String getFilter();
  
  	/**
  	 * Return the reference listeners to receive bind and unbind events.
  	 * 
  	 * This is specified by the <code>reference-listener</code> elements of the
  	 * service reference.
  	 * 
  	 * @return An immutable Collection of {@link ReferenceListener} objects to
  	 *         receive bind and unbind events. The Collection is empty if no
  	 *         reference listeners are specified for the service reference.
  	 */
  	Collection<ReferenceListener> getReferenceListeners();
  }
  