org.apache.felix.dependencymanager/src/main/java/org/apache/felix/dependencymanager/Service.java

/*
 *   Copyright 2006 The Apache Software 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.
 *
 */
package org.apache.felix.dependencymanager;

import java.util.Dictionary;
import java.util.List;

import org.osgi.framework.ServiceRegistration;

/**
 * Service interface.
 * 
 * @author Marcel Offermans
 */
public interface Service {
    /**
     * Adds a new dependency to this service.
     * 
     * @param dependency the dependency to add
     * @return this service
     */
    public Service add(Dependency dependency);
    
    /**
     * Removes a dependency from this service.
     * 
     * @param dependency the dependency to remove
     * @return this service
     */
    public Service remove(Dependency dependency);

    /**
     * Sets the public interface under which this service should be registered
     * in the OSGi service registry.
     *  
     * @param serviceName the name of the service interface
     * @param properties the properties for this service
     * @return this service
     */
    public Service setInterface(String serviceName, Dictionary properties);
    /**
     * Sets the public interfaces under which this service should be registered
     * in the OSGi service registry.
     *  
     * @param serviceNames the names of the service interface
     * @param properties the properties for this service
     * @return this service
     */
    public Service setInterface(String[] serviceNames, Dictionary properties);
    
    /**
     * Sets the implementation for this service. You can actually specify
     * an instance you have instantiated manually, or a <code>Class</code>
     * that will be instantiated using its default constructor when the
     * required dependencies are resolved (effectively giving you a lazy
     * instantiation mechanism).
     * 
     * There are four special methods that are called when found through
     * reflection to give you some life-cycle management options:
     * <ol>
     * <li><code>init()</code> when the implementation should be initialized,
     * before it is actually registered as a service (if at all)</li>
     * <li><code>start()</code> when the implementation has been registered
     * as a service (if at all)</li>
     * <li><code>stop()</code> when the implementation will be stopped, just
     * before the service will go away (if it had been registered)</li>
     * <li><code>destroy()</code>after the service has gone away (if it had
     * been registered)</li>
     * </ol>
     * In short, this allows you to initialize your instance before it is
     * registered, perform some post-initialization and pre-destruction code
     * as well as final cleanup. If a method is not defined, it simply is not
     * called, so you can decide which one(s) you need.
     * 
     * @param implementation the implementation
     * @return this service
     */
    public Service setImplementation(Object implementation);
    
    /**
     * Returns a list of dependencies.
     * 
     * @return a list of dependencies
     */
    public List getDependencies();
    
    /**
     * Returns the service registration for this service. The method
     * will return <code>null</code> if no service registration is
     * available.
     * 
     * @return the service registration
     */
    public ServiceRegistration getServiceRegistration();
    
    /**
     * Returns the service instance for this service. The method will
     * return <code>null</code> if no service instance is available.
     * 
     * @return the service instance
     */
    public Object getService();

    /**
     * Returns the service properties associated with the service.
     * 
     * @return the properties or <code>null</code> if there are none
     */
    public Dictionary getServiceProperties();
    
    /**
     * Sets the service properties associated with the service. If the service
     * was already registered, it will be updated.
     * 
     * @param serviceProperties the properties
     */
    public void setServiceProperties(Dictionary serviceProperties);
    
    /**
     * Sets the names of the methods used as callbacks. These methods, when found, are
     * invoked as part of the life-cycle management of the service implementation. The
     * methods should not have any parameters.
     * 
     * @param init the name of the init method
     * @param start the name of the start method
     * @param stop the name of the stop method
     * @param destroy the name of the destroy method
     * @return the service instance
     */
    public Service setCallbacks(String init, String start, String stop, String destroy);

    // listener
    /**
     * Adds a service state listener to this service.
     * 
     * @param listener the state listener
     */
    public void addStateListener(ServiceStateListener listener);

    /**
     * Removes a service state listener from this service.
     * 
     * @param listener the state listener
     */
    public void removeStateListener(ServiceStateListener listener);
    
    // events, must be fired when the dependency is started/active
    
    /**
     * Will be called when the dependency becomes available.
     * 
     * @param dependency the dependency
     */
    public void dependencyAvailable(Dependency dependency);
    
    /**
     * Will be called when the dependency changes.
     * 
     * @param dependency the dependency
     */
    public void dependencyUnavailable(Dependency dependency);
    
    /**
     * Will be called when the dependency becomes unavailable.
     * 
     * @param dependency the dependency
     */
    public void dependencyChanged(Dependency dependency);

    /**
     * Starts the service. This activates the dependency tracking mechanism
     * for this service.
     */
    public void start();
    
    /**
     * Stops the service. This deactivates the dependency tracking mechanism
     * for this service.
     */
    public void stop();
}