org.osgi.compendium/src/main/java/org/osgi/service/cm/ManagedServiceFactory.java

/*
 * $Header: /cvshome/build/org.osgi.service.cm/src/org/osgi/service/cm/ManagedServiceFactory.java,v 1.12 2006/07/11 00:54:03 hargrave Exp $
 *
 * Copyright (c) OSGi Alliance (2001, 2006). 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.cm;

import java.util.Dictionary;

/**
 * Manage multiple service instances.
 * 
 * Bundles registering this interface are giving the Configuration Admin service
 * the ability to create and configure a number of instances of a service that
 * the implementing bundle can provide. For example, a bundle implementing a
 * DHCP server could be instantiated multiple times for different interfaces
 * using a factory.
 * 
 * <p>
 * Each of these <i>service instances </i> is represented, in the persistent
 * storage of the Configuration Admin service, by a factory
 * <code>Configuration</code> object that has a PID. When such a
 * <code>Configuration</code> is updated, the Configuration Admin service
 * calls the <code>ManagedServiceFactory</code> updated method with the new
 * properties. When <code>updated</code> is called with a new PID, the Managed
 * Service Factory should create a new factory instance based on these
 * configuration properties. When called with a PID that it has seen before, it
 * should update that existing service instance with the new configuration
 * information.
 * 
 * <p>
 * In general it is expected that the implementation of this interface will
 * maintain a data structure that maps PIDs to the factory instances that it has
 * created. The semantics of a factory instance are defined by the Managed
 * Service Factory. However, if the factory instance is registered as a service
 * object with the service registry, its PID should match the PID of the
 * corresponding <code>Configuration</code> object (but it should <b>not </b>
 * be registered as a Managed Service!).
 * 
 * <p>
 * An example that demonstrates the use of a factory. It will create serial
 * ports under command of the Configuration Admin service.
 * 
 * <pre>
 *  
 *   class SerialPortFactory
 *     implements ManagedServiceFactory {
 *     ServiceRegistration registration;
 *     Hashtable ports;
 *     void start(BundleContext context) {
 *       Hashtable properties = new Hashtable();
 *       properties.put( Constants.SERVICE_PID,
 *         &quot;com.acme.serialportfactory&quot; );
 *       registration = context.registerService(
 *         ManagedServiceFactory.class.getName(),
 *         this,
 *         properties
 *       );
 *     }
 *     public void updated( String pid,
 *       Dictionary properties  ) {
 *       String portName = (String) properties.get(&quot;port&quot;);
 *       SerialPortService port =
 *         (SerialPort) ports.get( pid );
 *       if ( port == null ) {
 *         port = new SerialPortService();
 *         ports.put( pid, port );
 *         port.open();
 *       }
 *       if ( port.getPortName().equals(portName) )
 *         return;
 *       port.setPortName( portName );
 *     }
 *     public void deleted( String pid ) {
 *       SerialPortService port =
 *         (SerialPort) ports.get( pid );
 *       port.close();
 *       ports.remove( pid );
 *     }
 *     ...
 *   }
 *   
 * </pre>
 * 
 * @version $Revision: 1.12 $
 */
public interface ManagedServiceFactory {
	/**
	 * Return a descriptive name of this factory.
	 * 
	 * @return the name for the factory, which might be localized
	 */
	public String getName();

	/**
	 * Create a new instance, or update the configuration of an existing
	 * instance.
	 * 
	 * If the PID of the <code>Configuration</code> object is new for the
	 * Managed Service Factory, then create a new factory instance, using the
	 * configuration <code>properties</code> provided. Else, update the
	 * service instance with the provided <code>properties</code>.
	 * 
	 * <p>
	 * If the factory instance is registered with the Framework, then the
	 * configuration <code>properties</code> should be copied to its registry
	 * properties. This is not mandatory and security sensitive properties
	 * should obviously not be copied.
	 * 
	 * <p>
	 * If this method throws any <code>Exception</code>, the Configuration
	 * Admin service must catch it and should log it.
	 * 
	 * <p>
	 * When the implementation of updated detects any kind of error in the
	 * configuration properties, it should create a new
	 * {@link ConfigurationException} which describes the problem.
	 * 
	 * <p>
	 * The Configuration Admin service must call this method asynchronously.
	 * This implies that implementors of the <code>ManagedServiceFactory</code>
	 * class can be assured that the callback will not take place during
	 * registration when they execute the registration in a synchronized method.
	 * 
	 * @param pid The PID for this configuration.
	 * @param properties A copy of the configuration properties. This argument
	 *        must not contain the service.bundleLocation" property. The value
	 *        of this property may be obtained from the
	 *        <code>Configuration.getBundleLocation</code> method.
	 * @throws ConfigurationException when the configuration properties are
	 *         invalid.
	 */
	public void updated(String pid, Dictionary properties)
			throws ConfigurationException;

	/**
	 * Remove a factory instance.
	 * 
	 * Remove the factory instance associated with the PID. If the instance was
	 * registered with the service registry, it should be unregistered.
	 * <p>
	 * If this method throws any <code>Exception</code>, the Configuration
	 * Admin service must catch it and should log it.
	 * <p>
	 * The Configuration Admin service must call this method asynchronously.
	 * 
	 * @param pid the PID of the service to be removed
	 */
	public void deleted(String pid);
}