dependencymanager/org.apache.felix.dependencymanager/src/org/apache/felix/dm/impl/ComponentImpl.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.felix.dm.impl;

import static org.apache.felix.dm.ComponentState.INACTIVE;
import static org.apache.felix.dm.ComponentState.INSTANTIATED_AND_WAITING_FOR_REQUIRED;
import static org.apache.felix.dm.ComponentState.TRACKING_OPTIONAL;
import static org.apache.felix.dm.ComponentState.WAITING_FOR_REQUIRED;

import java.lang.reflect.Constructor;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Dictionary;
import java.util.Enumeration;
import java.util.HashMap;
import java.util.Hashtable;
import java.util.List;
import java.util.Map;
import java.util.Set;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ConcurrentSkipListSet;
import java.util.concurrent.CopyOnWriteArrayList;
import java.util.concurrent.Executor;
import java.util.concurrent.atomic.AtomicBoolean;
import java.util.concurrent.atomic.AtomicLong;

import org.apache.felix.dm.Component;
import org.apache.felix.dm.ComponentDeclaration;
import org.apache.felix.dm.ComponentDependencyDeclaration;
import org.apache.felix.dm.ComponentState;
import org.apache.felix.dm.ComponentStateListener;
import org.apache.felix.dm.Dependency;
import org.apache.felix.dm.DependencyManager;
import org.apache.felix.dm.Logger;
import org.apache.felix.dm.context.ComponentContext;
import org.apache.felix.dm.context.DependencyContext;
import org.apache.felix.dm.context.EventType;
import org.apache.felix.dm.context.Event;
import org.osgi.framework.Bundle;
import org.osgi.framework.BundleContext;
import org.osgi.framework.ServiceRegistration;
import org.osgi.service.log.LogService;

/**
 * Dependency Manager Component implementation.
 * 
 * @author <a href="mailto:dev@felix.apache.org">Felix Project Team</a>
 */
public class ComponentImpl implements Component, ComponentContext, ComponentDeclaration {
	private static final ServiceRegistration NULL_REGISTRATION = (ServiceRegistration) Proxy
			.newProxyInstance(ComponentImpl.class.getClassLoader(),
					new Class[] { ServiceRegistration.class },
					new DefaultNullObject());
    private static final Class<?>[] VOID = new Class[] {};
	private volatile Executor m_executor = new SerialExecutor(new Logger(null));
	private ComponentState m_state = ComponentState.INACTIVE;
	private final CopyOnWriteArrayList<DependencyContext> m_dependencies = new CopyOnWriteArrayList<>();
	private final List<ComponentStateListener> m_listeners = new CopyOnWriteArrayList<>();
	private boolean m_isStarted;
    private final Logger m_logger;
    private final BundleContext m_context;
    private final DependencyManager m_manager;
    private Object m_componentDefinition;
	private Object m_componentInstance;
    private volatile Object m_serviceName;
    private volatile Dictionary<Object, Object> m_serviceProperties;
    private volatile ServiceRegistration m_registration;
    private final Map<Class<?>, Boolean> m_autoConfig = new ConcurrentHashMap<>();
    private final Map<Class<?>, String> m_autoConfigInstance = new ConcurrentHashMap<>();
    private final Map<String, Long> m_stopwatch = new ConcurrentHashMap<>();
    private final long m_id;
    private static AtomicLong m_idGenerator = new AtomicLong();
    // Holds all the services of a given dependency context. Caution: the last entry in the skiplist is the highest ranked service.
    private final Map<DependencyContext, ConcurrentSkipListSet<Event>> m_dependencyEvents = new HashMap<>();
    private final AtomicBoolean m_active = new AtomicBoolean(false);
        
    public Component setDebug(String debugKey) {
    	// Force debug level in our logger
        m_logger.setEnabledLevel(LogService.LOG_DEBUG);
        m_logger.setDebugKey(debugKey);
    	return this;
    }

    // configuration (static)
    private volatile String m_callbackInit;
    private volatile String m_callbackStart;
    private volatile String m_callbackStop;
    private volatile String m_callbackDestroy;
    private volatile Object m_callbackInstance;
    
    // instance factory
	private volatile Object m_instanceFactory;
	private volatile String m_instanceFactoryCreateMethod;
	
	// composition manager
	private volatile Object m_compositionManager;
	private volatile String m_compositionManagerGetMethod;
	private volatile Object m_compositionManagerInstance;
    private final Bundle m_bundle;
	
    static class SCDImpl implements ComponentDependencyDeclaration {
        private final String m_name;
        private final int m_state;
        private final String m_type;

        public SCDImpl(String name, int state, String type) {
            m_name = name;
            m_state = state;
            m_type = type;
        }

        public String getName() {
            return m_name;
        }
        
        public String getSimpleName() {
            return m_name;
        }
        
        public String getFilter() {
            return null;
        }

        public int getState() {
            return m_state;
        }

        public String getType() {
            return m_type;
        }
    }

    public ComponentImpl() {
	    this(null, null, new Logger(null));
	}
	
    public ComponentImpl(BundleContext context, DependencyManager manager, Logger logger) {
        m_context = context;
        m_bundle = context != null ? context.getBundle() : null;
        m_manager = manager;
        m_logger = logger;
        m_autoConfig.put(BundleContext.class, Boolean.TRUE);
        m_autoConfig.put(ServiceRegistration.class, Boolean.TRUE);
        m_autoConfig.put(DependencyManager.class, Boolean.TRUE);
        m_autoConfig.put(Component.class, Boolean.TRUE);
        m_callbackInit = "init";
        m_callbackStart = "start";
        m_callbackStop = "stop";
        m_callbackDestroy = "destroy";
        m_id = m_idGenerator.getAndIncrement();
    }

	@Override
	public Component add(final Dependency ... dependencies) {
		getExecutor().execute(new Runnable() {
			@Override
			public void run() {
				List<DependencyContext> instanceBoundDeps = new ArrayList<>();
				for (Dependency d : dependencies) {
					DependencyContext dc = (DependencyContext) d;
					if (dc.getComponentContext() != null) {
                        m_logger.err("%s can't be added to %s (dependency already added to another component).", dc,
                            ComponentImpl.this);
                        continue;
					}
					m_dependencyEvents.put(dc,  new ConcurrentSkipListSet<Event>());
					m_dependencies.add(dc);
					dc.setComponentContext(ComponentImpl.this);
					if (!(m_state == ComponentState.INACTIVE)) {
						dc.setInstanceBound(true);
						instanceBoundDeps.add(dc);
					}
				}
				startDependencies(instanceBoundDeps);
				handleChange();
			}
		});
		return this;
	}

	@Override
	public Component remove(final Dependency d) {
		getExecutor().execute(new Runnable() {
			@Override
			public void run() {
				DependencyContext dc = (DependencyContext) d;
				// First remove this dependency from the dependency list
                m_dependencies.remove(d);
                // Now we can stop the dependency (our component won't be deactivated, it will only be unbound with
                // the removed dependency).
				if (!(m_state == ComponentState.INACTIVE)) {
					dc.stop();
				}
				// Finally, cleanup the dependency events.
                m_dependencyEvents.remove(d);
				handleChange();
			}
		});
		return this;
	}

	public void start() {
	    if (m_active.compareAndSet(false, true)) {
            getExecutor().execute(new Runnable() {
                @Override
                public void run() {
                    m_isStarted = true;
                    handleChange();
                }
            });
	    }
	}
	
	public void stop() {           
	    if (m_active.compareAndSet(true, false)) {
	        Executor executor = getExecutor();

	        // First, declare the task that will stop our component in our executor.
	        final Runnable stopTask = new Runnable() {
                @Override
                public void run() {
                	m_isStarted = false;
                	handleChange();
                }
            };
            
            // Now, we have to schedule our stopTask in our component executor. But we have to handle a special case:
            // if the component bundle is stopping *AND* if the executor is a parallel dispatcher, then we want 
            // to invoke our stopTask synchronously, in order to make sure that the bundle context is valid while our 
            // component is being deactivated (if we stop the component asynchronously, the bundle context may be invalidated
            // before our component is stopped, and we don't want to be in this situation).
            
            boolean stopping = m_bundle != null /* null only in tests env */ && m_bundle.getState() == Bundle.STOPPING;
            if (stopping && executor instanceof DispatchExecutor) {
            	((DispatchExecutor) executor).execute(stopTask, false /* try to  execute synchronously, not using threadpool */);
            } else {
            	executor.execute(stopTask);
            }
	    }
	}

	@SuppressWarnings("unchecked")
    @Override
	public Component setInterface(String serviceName, Dictionary<?, ?> properties) {
		ensureNotActive();
	    m_serviceName = serviceName;
	    m_serviceProperties = (Dictionary<Object, Object>) properties;
	    return this;
	}

	@SuppressWarnings("unchecked")
    @Override
	public Component setInterface(String[] serviceName, Dictionary<?, ?> properties) {
	    ensureNotActive();
	    m_serviceName = serviceName;
	    m_serviceProperties = (Dictionary<Object, Object>) properties;
	    return this;
	}
	
	@Override
    public void handleEvent(final DependencyContext dc, final EventType type, final Event... event) {
        // since this method can be invoked by anyone from any thread, we need to
        // pass on the event to a runnable that we execute using the component's
        // executor
        getExecutor().execute(new Runnable() {
            @Override
            public void run() {
                switch (type) {
                case ADDED:
                    handleAdded(dc, event[0]);
                    break;
                case CHANGED:
                    handleChanged(dc, event[0]);
                    break;
                case REMOVED:
                    handleRemoved(dc, event[0]);
                    break;
                case SWAPPED:
                    handleSwapped(dc, event[0], event[1]);
                    break;
                }
            }
        });
	}

    @Override
    public Event getDependencyEvent(DependencyContext dc) {
        ConcurrentSkipListSet<Event> events = m_dependencyEvents.get(dc);
        return events.size() > 0 ? events.last() : null;
    }
    
    @Override
    public Set<Event> getDependencyEvents(DependencyContext dc) {
        return m_dependencyEvents.get(dc);
    }

    public Component setAutoConfig(Class<?> clazz, boolean autoConfig) {
        m_autoConfig.put(clazz, Boolean.valueOf(autoConfig));
        return this;
    }
    
    public Component setAutoConfig(Class<?> clazz, String instanceName) {
        m_autoConfig.put(clazz, Boolean.valueOf(instanceName != null));
        m_autoConfigInstance.put(clazz, instanceName);
        return this;
    }
    
    public boolean getAutoConfig(Class<?> clazz) {
        Boolean result = (Boolean) m_autoConfig.get(clazz);
        return (result != null && result.booleanValue());
    }
    
    public String getAutoConfigInstance(Class<?> clazz) {
        return (String) m_autoConfigInstance.get(clazz);
    }

    private void handleAdded(DependencyContext dc, Event e) {
        if (! m_isStarted) {
            return;
        }
        m_logger.debug("handleAdded %s", e);
        
        Set<Event> dependencyEvents = m_dependencyEvents.get(dc);
        dependencyEvents.add(e);        
        dc.setAvailable(true);
        
        // In the following switch block, we sometimes only recalculate state changes 
        // if the dependency is fully started. If the dependency is not started,
        // it means it is actually starting (the service tracker is executing the open method). 
        // And in this case, depending on the state, we don't recalculate state changes now. We'll do it 
        // once all currently available services are found, and then after, 
        // we'll recalculate state change (see the startDependencies method). 
        // 
        // All this is done for two reasons:
        // 1- optimization: it is preferable to recalculate state changes once we know about all currently 
        //    available dependency services (after the tracker has returned from its open method).
        // 2- This also allows to determine the list of currently available dependency services from within 
        //    the component start method callback (this will be extremely useful when porting the Felix SCR 
        //    on top of DM4).
        
        switch (m_state) {
        case WAITING_FOR_REQUIRED:            
            if (dc.isStarted() && dc.isRequired()) {
                // if dependency is starting, we'll handle change after the tracker has returned (see startDependencies method).
                handleChange();
            }
            break;
        case INSTANTIATED_AND_WAITING_FOR_REQUIRED:
            if (!dc.isInstanceBound()) {
                if (dc.isRequired()) {
                    dc.invokeCallback(EventType.ADDED, e);
                }
                updateInstance(dc, e, false, true);
            } else {
                if (dc.isStarted() && dc.isRequired()) {
                    // if dependency is starting, we'll handle change after the tracker has returned (see startDependencies method).
                    handleChange();
                }
            }
            break;
        case TRACKING_OPTIONAL:
            dc.invokeCallback(EventType.ADDED, e);
            updateInstance(dc, e, false, true);
            break;
        default:
        }
    }
        
    private void handleChanged(final DependencyContext dc, final Event e) {
        if (! m_isStarted) {
            return;
        }
        Set<Event> dependencyEvents = m_dependencyEvents.get(dc);
        dependencyEvents.remove(e);
        dependencyEvents.add(e);
        
        switch (m_state) {
        case TRACKING_OPTIONAL:
            dc.invokeCallback(EventType.CHANGED, e);
            updateInstance(dc, e, true, false);
            break;

        case INSTANTIATED_AND_WAITING_FOR_REQUIRED:
            if (!dc.isInstanceBound()) {
                dc.invokeCallback(EventType.CHANGED, e);
                updateInstance(dc, e, true, false);
            }
            break;
        default:
            // noop
        }
    }
    
    private void handleRemoved(DependencyContext dc, Event e) {
        if (! m_isStarted) {
            return;
        }
        // Check if the dependency is still available.
        Set<Event> dependencyEvents = m_dependencyEvents.get(dc);
        int size = dependencyEvents.size();
        if (dependencyEvents.contains(e)) {
            size--; // the dependency is currently registered and is about to be removed.
        }
        dc.setAvailable(size > 0);
        
        // If the dependency is now unavailable, we have to recalculate state change. This will result in invoking the
        // "removed" callback with the removed dependency (which we have not yet removed from our dependency events list.).
        // But we don't recalculate the state if the dependency is not started (if not started, it means that it is currently starting,
        // and the tracker is detecting a removed service).
        if (size == 0 && dc.isStarted()) {
            handleChange();
        }
        
        // Now, really remove the dependency event.
        dependencyEvents.remove(e);    
        
        // Depending on the state, we possible have to invoke the callbacks and update the component instance.        
        switch (m_state) {
        case INSTANTIATED_AND_WAITING_FOR_REQUIRED:
            if (!dc.isInstanceBound()) {
                if (dc.isRequired()) {
                    dc.invokeCallback(EventType.REMOVED, e);
                }
                updateInstance(dc, e, false, false);
            }
            break;
        case TRACKING_OPTIONAL:
            dc.invokeCallback(EventType.REMOVED, e);
            updateInstance(dc, e, false, false);
            break;
        default:
        }
    }
    
    private void handleSwapped(DependencyContext dc, Event oldEvent, Event newEvent) {
        if (! m_isStarted) {
            return;
        }
        Set<Event> dependencyEvents = m_dependencyEvents.get(dc);        
        dependencyEvents.remove(oldEvent);
        dependencyEvents.add(newEvent);
                
        // Depending on the state, we possible have to invoke the callbacks and update the component instance.        
        switch (m_state) {
        case WAITING_FOR_REQUIRED:
            // No need to swap, we don't have yet injected anything
            break;
        case INSTANTIATED_AND_WAITING_FOR_REQUIRED:
            // Only swap *non* instance-bound dependencies
            if (!dc.isInstanceBound()) {
                if (dc.isRequired()) {
                    dc.invokeCallback(EventType.SWAPPED, oldEvent, newEvent);
                }
            }
            break;
        case TRACKING_OPTIONAL:
            dc.invokeCallback(EventType.SWAPPED, oldEvent, newEvent);
            break;
        default:
        }
    }
    
	private void handleChange() {
	    m_logger.debug("handleChanged");
		try {
			ComponentState oldState;
			ComponentState newState;
			do {
				oldState = m_state;
				newState = calculateNewState(oldState);
				m_logger.debug("%s -> %s", oldState, newState);
				m_state = newState;
			} while (performTransition(oldState, newState));
		} finally {
		    m_logger.debug("end handling change.");
		}
	}
    
	/** Based on the current state, calculate the new state. */
	private ComponentState calculateNewState(ComponentState currentState) {
		if (currentState == INACTIVE) {
			if (m_isStarted) {
				return WAITING_FOR_REQUIRED;
			}
		}
		if (currentState == WAITING_FOR_REQUIRED) {
			if (!m_isStarted) {
				return INACTIVE;
			}
			if (allRequiredAvailable()) {
				return INSTANTIATED_AND_WAITING_FOR_REQUIRED;
			}
		}
		if (currentState == INSTANTIATED_AND_WAITING_FOR_REQUIRED) {
			if (m_isStarted && allRequiredAvailable()) {
				if (allInstanceBoundAvailable()) {
					return TRACKING_OPTIONAL;
				}
				return currentState;
			}
			return WAITING_FOR_REQUIRED;
		}
		if (currentState == TRACKING_OPTIONAL) {
			if (m_isStarted && allRequiredAvailable() && allInstanceBoundAvailable()) {
				return currentState;
			}
			return INSTANTIATED_AND_WAITING_FOR_REQUIRED;
		}
		return currentState;
	}

	/** Perform all the actions associated with state transitions. Returns true if a transition was performed. */
	private boolean performTransition(ComponentState oldState, ComponentState newState) {
//		System.out.println("transition from " + oldState + " to " + newState);
		if (oldState == ComponentState.INACTIVE && newState == ComponentState.WAITING_FOR_REQUIRED) {
		    startDependencies(m_dependencies);
			notifyListeners(newState);
			return true;
		}
		if (oldState == ComponentState.WAITING_FOR_REQUIRED && newState == ComponentState.INSTANTIATED_AND_WAITING_FOR_REQUIRED) {
			instantiateComponent();
            invokeAutoConfigDependencies();
			invokeAddRequiredDependencies();
			ComponentState stateBeforeCallingInit = m_state;
	        invoke(m_callbackInit); 
	        if (stateBeforeCallingInit == m_state) {
	            notifyListeners(newState); // init did not change current state, we can notify about this new state
	        }
			return true;
		}
		if (oldState == ComponentState.INSTANTIATED_AND_WAITING_FOR_REQUIRED && newState == ComponentState.TRACKING_OPTIONAL) {
            invokeAutoConfigInstanceBoundDependencies();
			invokeAddRequiredInstanceBoundDependencies();
			invoke(m_callbackStart);
			invokeAddOptionalDependencies();
			registerService();
			notifyListeners(newState);
			return true;
		}
		if (oldState == ComponentState.TRACKING_OPTIONAL && newState == ComponentState.INSTANTIATED_AND_WAITING_FOR_REQUIRED) {
		    unregisterService();
		    invokeRemoveOptionalDependencies();
			invoke(m_callbackStop);
			invokeRemoveInstanceBoundDependencies();
			notifyListeners(newState);
			return true;
		}
		if (oldState == ComponentState.INSTANTIATED_AND_WAITING_FOR_REQUIRED && newState == ComponentState.WAITING_FOR_REQUIRED) {
			invoke(m_callbackDestroy);
			invokeRemoveRequiredDependencies();
			notifyListeners(newState);
			if (! someDependenciesNeedInstance()) {
                destroyComponent();
            }
			return true;
		}
		if (oldState == ComponentState.WAITING_FOR_REQUIRED && newState == ComponentState.INACTIVE) {
		    stopDependencies();
            destroyComponent();
			notifyListeners(newState);
			return true;
		}
		return false;
	}
	
    private boolean allRequiredAvailable() {
        boolean available = true;
        for (DependencyContext d : m_dependencies) {
            if (d.isRequired() && !d.isInstanceBound()) {
                if (!d.isAvailable()) {
                    available = false;
                    break;
                }
            }
        }
        return available;
    }

    private boolean allInstanceBoundAvailable() {
        boolean available = true;
        for (DependencyContext d : m_dependencies) {
            if (d.isRequired() && d.isInstanceBound()) {
                if (!d.isAvailable()) {
                    available = false;
                    break;
                }
            }
        }
        return available;
    }

    private boolean someDependenciesNeedInstance() {
        for (DependencyContext d : m_dependencies) {
            if (d.needsInstance()) {
                return true;
            }
        }
        return false;
    }
    
    /**
     * Updates the component instance(s).
     * @param dc the dependency context for the updating dependency service
     * @param event the event holding the updating service (service + properties)
     * @param update true if dependency service properties are updating, false if not. If false, it means
     *        that a dependency service is being added or removed. (see the "add" flag).
     * @param add true if the dependency service has been added, false if it has been removed. This flag is 
     *        ignored if the "update" flag is true (because the dependency properties are just being updated).
     */
    private void updateInstance(DependencyContext dc, Event event, boolean update, boolean add) {
        if (dc.isAutoConfig()) {
            updateImplementation(dc.getAutoConfigType(), dc, dc.getAutoConfigName(), event, update, add);
        }
        if (dc.isPropagated() && m_registration != null) {
            m_registration.setProperties(calculateServiceProperties());
        }
    }
    
    private void startDependencies(List<DependencyContext> dependencies) {
        // Start first optional dependencies first.
        m_logger.debug("startDependencies.");
        List<DependencyContext> requiredDeps = new ArrayList<>();
        for (DependencyContext d : dependencies) {
            if (d.isRequired()) {
                requiredDeps.add(d);
                continue;
            }
            if (d.needsInstance()) {
                instantiateComponent();
            }
            d.start();
        }
        // now, start required dependencies.
        for (DependencyContext d : requiredDeps) {
            if (d.needsInstance()) {
                instantiateComponent();
            }
            d.start();
        }
        // The started dependencies has probably called our handleAdded method: we now have to run our state machine.
        handleChange();
    }
    
    private void stopDependencies() {
        for (DependencyContext d : m_dependencies) {
            d.stop();
        }
    }

    private void registerService() {
        if (m_context != null && m_serviceName != null) {
            ServiceRegistrationImpl wrapper = new ServiceRegistrationImpl();
            m_registration = wrapper;
            autoConfigureImplementation(ServiceRegistration.class, m_registration);
            
            // service name can either be a string or an array of strings
            ServiceRegistration registration;

            // determine service properties
            Dictionary<?,?> properties = calculateServiceProperties();

            // register the service
            try {
                if (m_serviceName instanceof String) {
                    registration = m_context.registerService((String) m_serviceName, m_componentInstance, properties);
                }
                else {
                    registration = m_context.registerService((String[]) m_serviceName, m_componentInstance, properties);
                }
                wrapper.setServiceRegistration(registration);
            }
            catch (IllegalArgumentException iae) {
                m_logger.log(Logger.LOG_ERROR, "Could not register service " + m_componentInstance, iae);
                // set the registration to an illegal state object, which will make all invocations on this
                // wrapper fail with an ISE (which also occurs when the SR becomes invalid)
                wrapper.setIllegalState();
            }
        }
    }

    private void unregisterService() {
        if (m_serviceName != null && m_registration != null) {
            try {
                if (m_bundle != null && m_bundle.getState() == Bundle.ACTIVE) {
                    m_registration.unregister();
                }
            } catch (IllegalStateException e) { /* Should we really log this ? */}
            autoConfigureImplementation(ServiceRegistration.class, NULL_REGISTRATION);
            m_registration = null;
        }
    }
    
    private Dictionary<Object, Object> calculateServiceProperties() {
		Dictionary<Object, Object> properties = new Hashtable<>();
		for (int i = 0; i < m_dependencies.size(); i++) {
			DependencyContext d = (DependencyContext) m_dependencies.get(i);
			if (d.isPropagated() && d.isAvailable()) {
				Dictionary<Object, Object> dict = d.getProperties();
				addTo(properties, dict);
			}
		}
		// our service properties must not be overriden by propagated dependency properties, so we add our service
		// properties after having added propagated dependency properties.
		addTo(properties, m_serviceProperties);
		if (properties.size() == 0) {
			properties = null;
		}
		return properties;
	}

	private void addTo(Dictionary<Object, Object> properties, Dictionary<Object, Object> additional) {
		if (properties == null) {
			throw new IllegalArgumentException("Dictionary to add to cannot be null.");
		}
		if (additional != null) {
			Enumeration<Object> e = additional.keys();
			while (e.hasMoreElements()) {
				Object key = e.nextElement();
				properties.put(key, additional.get(key));
			}
		}
	}

	void instantiateComponent() {
        m_logger.debug("instantiating component.");

		// TODO add more complex factory instantiations of one or more components in a composition here
	    if (m_componentInstance == null) {
            if (m_componentDefinition instanceof Class) {
                try {
                    m_componentInstance = createInstance((Class<?>) m_componentDefinition);
                }
                catch (Exception e) {
                    m_logger.log(Logger.LOG_ERROR, "Could not instantiate class " + m_componentDefinition, e);
                }
            }
            else {
	        	if (m_instanceFactoryCreateMethod != null) {
	        		Object factory = null;
		        	if (m_instanceFactory != null) {
		        		if (m_instanceFactory instanceof Class) {
		        			try {
								factory = createInstance((Class<?>) m_instanceFactory);
							}
		                    catch (Exception e) {
		                        m_logger.log(Logger.LOG_ERROR, "Could not create factory instance of class " + m_instanceFactory + ".", e);
		                    }
		        		}
		        		else {
		        			factory = m_instanceFactory;
		        		}
		        	}
		        	else {
		        		// TODO review if we want to try to default to something if not specified
		        	    // for now the JavaDoc of setFactory(method) reflects the fact that we need
		        	    // to review it
		        	}
		        	if (factory == null) {
                        m_logger.log(Logger.LOG_ERROR, "Factory cannot be null.");
		        	}
		        	else {
    		        	try {
    		        		m_componentInstance = InvocationUtil.invokeMethod(factory, 
    		        		    factory.getClass(), m_instanceFactoryCreateMethod, 
    		        		    new Class[][] {{}, {Component.class}}, new Object[][] {{}, {this}}, false);
    					}
    		        	catch (Exception e) {
    	                    m_logger.log(Logger.LOG_ERROR, "Could not create service instance using factory " + factory + " method " + m_instanceFactoryCreateMethod + ".", e);
    					}
		        	}
	        	}
            }
            
            if (m_componentInstance == null) {
                m_componentInstance = m_componentDefinition;
            }
            
	        // configure the bundle context
            autoConfigureImplementation(BundleContext.class, m_context);
            autoConfigureImplementation(ServiceRegistration.class, NULL_REGISTRATION);
            autoConfigureImplementation(DependencyManager.class, m_manager);
            autoConfigureImplementation(Component.class, this);
	    }
	}
	
	private void destroyComponent() {
		m_componentInstance = null;
	}
	
	private void invokeAddRequiredDependencies() {
		for (DependencyContext d : m_dependencies) {
			if (d.isRequired() && !d.isInstanceBound()) {
			    for (Event e : m_dependencyEvents.get(d)) {
			        d.invokeCallback(EventType.ADDED, e);
			    }
			}
		}
	}
	
    private void invokeAutoConfigDependencies() {
        for (DependencyContext d : m_dependencies) {
            if (d.isAutoConfig() && !d.isInstanceBound()) {
                configureImplementation(d.getAutoConfigType(), d, d.getAutoConfigName());
            }
        }
    }
    
    private void invokeAutoConfigInstanceBoundDependencies() {
        for (DependencyContext d : m_dependencies) {
            if (d.isAutoConfig() && d.isInstanceBound()) {
                configureImplementation(d.getAutoConfigType(), d, d.getAutoConfigName());
            }
        }
    }
	
	private void invokeAddRequiredInstanceBoundDependencies() {
		for (DependencyContext d : m_dependencies) {
			if (d.isRequired() && d.isInstanceBound()) {
	             for (Event e : m_dependencyEvents.get(d)) {
	                 d.invokeCallback(EventType.ADDED, e);
	             }
			}
		}
	}
	
    private void invokeAddOptionalDependencies() {
        for (DependencyContext d : m_dependencies) {
            if (! d.isRequired()) {
                for (Event e : m_dependencyEvents.get(d)) {
                    d.invokeCallback(EventType.ADDED, e);
                }
            }
        }
    }

    private void invokeRemoveRequiredDependencies() { 
		for (DependencyContext d : m_dependencies) {
			if (!d.isInstanceBound() && d.isRequired()) {
                for (Event e : m_dependencyEvents.get(d)) {
                    d.invokeCallback(EventType.REMOVED, e);
                }
			}
		}
	}

    private void invokeRemoveOptionalDependencies() { 
        for (DependencyContext d : m_dependencies) {
            if (! d.isRequired()) {
                for (Event e : m_dependencyEvents.get(d)) {
                    d.invokeCallback(EventType.REMOVED, e);
                }
            }
        }
    }

	private void invokeRemoveInstanceBoundDependencies() {
		for (DependencyContext d : m_dependencies) {
			if (d.isInstanceBound()) {
                for (Event e : m_dependencyEvents.get(d)) {
                    d.invokeCallback(EventType.REMOVED, e);
                }
			}
		}
	}

	private void invoke(String name) {
        if (name != null) {
            // if a callback instance was specified, look for the method there, if not,
            // ask the service for its composition instances
            Object[] instances = m_callbackInstance != null ? new Object[] { m_callbackInstance } : getCompositionInstances();

            long t1 = System.nanoTime();
            try {
                invokeCallbackMethod(instances, name, 
                    new Class[][] {{ Component.class }, {}}, 
                    new Object[][] {{ this }, {}},
                    false);
            } finally {
                long t2 = System.nanoTime();
                m_stopwatch.put(name, t2 - t1);
            }
        }
    }
    
	@SuppressWarnings("unchecked")
    public <T> T getInstance() {     
	    Object[] instances  = getCompositionInstances();
	    return instances.length == 0 ? null : (T) instances[0]; 
    }

    public Object[] getInstances() {
    	return getCompositionInstances();
    }
    
    public void invokeCallbackMethod(Object[] instances, String methodName, Class<?>[][] signatures, Object[][] parameters) {
        invokeCallbackMethod(instances, methodName, signatures, parameters, true);
    }

    public void invokeCallbackMethod(Object[] instances, String methodName, Class<?>[][] signatures,
        Object[][] parameters, boolean logIfNotFound) {
        boolean callbackFound = false;
        for (int i = 0; i < instances.length; i++) {
            try {
                InvocationUtil.invokeCallbackMethod(instances[i], methodName, signatures, parameters);
                callbackFound |= true;
            }
            catch (NoSuchMethodException e) {
                // if the method does not exist, ignore it
            }
            catch (InvocationTargetException e) {
                // the method itself threw an exception, log that
                m_logger.log(Logger.LOG_ERROR, "Invocation of '" + methodName + "' failed.", e.getCause());
            }
            catch (Throwable e) {
                m_logger.log(Logger.LOG_ERROR, "Could not invoke '" + methodName + "'.", e);
            }
        }
        
        // If the callback is not found, we don't log if the method is on an AbstractDecorator.
        // (Aspect or Adapter are not interested in user dependency callbacks)        
        if (logIfNotFound && ! callbackFound && ! (getInstance() instanceof AbstractDecorator)) {
            if (m_logger == null) {
                System.out.println("Callback \"" + methodName + "\" not found on componnent instances "
                    + Arrays.toString(getInstances()));
            } else {
                m_logger.log(LogService.LOG_ERROR, "Callback \"" + methodName + "\" callback not found on componnent instances "
                    + Arrays.toString(getInstances()));
            }

        }
    }

   private Object createInstance(Class<?> clazz) throws SecurityException, NoSuchMethodException, InstantiationException, IllegalAccessException, IllegalArgumentException, InvocationTargetException {
		Constructor<?> constructor = clazz.getConstructor(VOID);
		constructor.setAccessible(true);
        return constructor.newInstance();
    }

	private void notifyListeners(ComponentState state) {
		for (ComponentStateListener l : m_listeners) {
			l.changed(this, state);
		}
	}
	
	@Override
	public boolean isAvailable() {
		return m_state == TRACKING_OPTIONAL;
	}
	
	@Override
	public boolean isActive() {
	    return m_active.get();
	}
	
	@Override
	public Component add(final ComponentStateListener l) {
	    m_listeners.add(l);
	    return this;
	}

	@Override
	public Component remove(ComponentStateListener l) {
	    m_listeners.remove(l);
	    return this;
	}

	@SuppressWarnings("unchecked")
    @Override
	public List<DependencyContext> getDependencies() {
		return (List<DependencyContext>) m_dependencies.clone();
	}

	@Override
	public Component setImplementation(Object implementation) {
		m_componentDefinition = implementation;
		return this;
	}
	
    private void autoConfigureImplementation(Class<?> clazz, Object instance) {
        if (((Boolean) m_autoConfig.get(clazz)).booleanValue()) {
            configureImplementation(clazz, instance, (String) m_autoConfigInstance.get(clazz));
        }
    }
    
   /**
     * Configure a field in the service implementation. The service implementation
     * is searched for fields that have the same type as the class that was specified
     * and for each of these fields, the specified instance is filled in.
     *
     * @param clazz the class to search for
     * @param instance the object to fill in the implementation class(es) field
     * @param instanceName the name of the instance to fill in, or <code>null</code> if not used
     */
    private void configureImplementation(Class<?> clazz, Object instance, String fieldName) {
        Object[] targets = getInstances();
        if (! FieldUtil.injectField(targets, fieldName, clazz, instance, m_logger) && fieldName != null) {
            // If the target is an abstract decorator (i.e: an adapter, or an aspect), we must not log warnings
            // if field has not been injected.
            if (! (getInstance() instanceof AbstractDecorator)) {
                m_logger.log(Logger.LOG_ERROR, "Could not inject " + instance + " to field \"" + fieldName
                    + "\" at any of the following component instances: " + Arrays.toString(targets));
            }
        }
    }

    private void configureImplementation(Class<?> clazz, DependencyContext dc, String fieldName) {
        Object[] targets = getInstances();
        if (! FieldUtil.injectDependencyField(targets, fieldName, clazz, dc, m_logger) && fieldName != null) {
            // If the target is an abstract decorator (i.e: an adapter, or an aspect), we must not log warnings
            // if field has not been injected.
            if (! (getInstance() instanceof AbstractDecorator)) {
                m_logger.log(Logger.LOG_ERROR, "Could not inject dependency " + clazz.getName() + " to field \""
                    + fieldName + "\" at any of the following component instances: " + Arrays.toString(targets));
            }
        }
    }

    /**
     * Update the component instances.
     *
     * @param clazz the class of the dependency service to inject in the component instances
     * @param dc the dependency context for the updating dependency service
     * @param fieldName the component instances fieldname to fill in with the updated dependency service
     * @param event the event holding the updating service (service + properties)
     * @param update true if dependency service properties are updating, false if not. If false, it means
     *        that a dependency service is being added or removed. (see the "add" flag).
     * @param add true if the dependency service has been added, false if it has been removed. This flag is 
     *        ignored if the "update" flag is true (because the dependency properties are just being updated).
     */
    private void updateImplementation(Class<?> clazz, DependencyContext dc, String fieldName, Event event, boolean update,
        boolean add)
    {
        Object[] targets = getInstances();
        FieldUtil.updateDependencyField(targets, fieldName, update, add, clazz, event, dc, m_logger);
    }

    @Override
	public ServiceRegistration getServiceRegistration() {
        return m_registration;
	}

	@SuppressWarnings("unchecked")
    @Override
	public <K,V> Dictionary<K, V> getServiceProperties() {
		if (m_serviceProperties != null) {
			// Applied patch from FELIX-4304
			Hashtable<Object, Object> serviceProperties = new Hashtable<>();
			addTo(serviceProperties, m_serviceProperties);
			return (Dictionary<K, V>) serviceProperties;
		}
		return null;
	}

	@Override
    @SuppressWarnings("unchecked")
	public Component setServiceProperties(final Dictionary<?, ?> serviceProperties) {
	    getExecutor().execute(new Runnable() {
            @Override
			public void run() {
			    Dictionary<Object, Object> properties = null;
		        m_serviceProperties = (Dictionary<Object, Object>) serviceProperties;
		        if ((m_registration != null) && (m_serviceName != null)) {
		            properties = calculateServiceProperties();
			        m_registration.setProperties(properties);
		        }
			}
		});
	    return this;
	}
	
	public Component setCallbacks(String init, String start, String stop, String destroy) {
	    ensureNotActive();
	    m_callbackInit = init;
	    m_callbackStart = start;
	    m_callbackStop = stop;
	    m_callbackDestroy = destroy;
	    return this;
	}
	
    public Component setCallbacks(Object instance, String init, String start, String stop, String destroy) {
	    ensureNotActive();
        m_callbackInstance = instance;
        m_callbackInit = init;
        m_callbackStart = start;
        m_callbackStop = stop;
        m_callbackDestroy = destroy;
        return this;
    }

	@Override
	public Component setFactory(Object factory, String createMethod) {
	    ensureNotActive();
		m_instanceFactory = factory;
		m_instanceFactoryCreateMethod = createMethod;
		return this;
	}

	@Override
	public Component setFactory(String createMethod) {
		return setFactory(null, createMethod);
	}

	@Override
	public Component setComposition(Object instance, String getMethod) {
	    ensureNotActive();
		m_compositionManager = instance;
		m_compositionManagerGetMethod = getMethod;
		return this;
	}

	@Override
	public Component setComposition(String getMethod) {
		return setComposition(null, getMethod);
	}

	private Object[] getCompositionInstances() {
        Object[] instances = null;
        if (m_compositionManagerGetMethod != null) {
            if (m_compositionManager != null) {
                m_compositionManagerInstance = m_compositionManager;
            }
            else {
                m_compositionManagerInstance = m_componentInstance;
            }
            if (m_compositionManagerInstance != null) {
                try {
                    instances = (Object[]) InvocationUtil.invokeMethod(m_compositionManagerInstance, m_compositionManagerInstance.getClass(), m_compositionManagerGetMethod, new Class[][] {{}}, new Object[][] {{}}, false);
                }
                catch (Exception e) {
                    m_logger.log(Logger.LOG_ERROR, "Could not obtain instances from the composition manager.", e);
                    instances = m_componentInstance == null ? new Object[] {} : new Object[] { m_componentInstance };
                }
            }
        }
        else {
            instances = m_componentInstance == null ? new Object[] {} : new Object[] { m_componentInstance };
        }
        return instances;
	}

	@Override
	public DependencyManager getDependencyManager() {
        return m_manager;
	}
	
    public ComponentDependencyDeclaration[] getComponentDependencies() {
        List<DependencyContext> deps = getDependencies();
        if (deps != null) {
            ComponentDependencyDeclaration[] result = new ComponentDependencyDeclaration[deps.size()];
            for (int i = 0; i < result.length; i++) {
                DependencyContext dep = (DependencyContext) deps.get(i);
                if (dep instanceof ComponentDependencyDeclaration) {
                    result[i] = (ComponentDependencyDeclaration) dep;
                }
                else {
                    result[i] = new SCDImpl(dep.toString(), (dep.isAvailable() ? 1 : 0) + (dep.isRequired() ? 2 : 0), dep.getClass().getName());
                }
            }
            return result;
        }
        return null;
    }
    
    public String getName() {
        StringBuffer sb = new StringBuffer();
        Object serviceName = m_serviceName;
        if (serviceName instanceof String[]) {
            String[] names = (String[]) serviceName;
            for (int i = 0; i < names.length; i++) {
                if (i > 0) {
                    sb.append(", ");
                }
                sb.append(names[i]);
            }
            appendProperties(sb);
        } else if (serviceName instanceof String) {
            sb.append(serviceName.toString());
            appendProperties(sb);
        } else {
            Object implementation = m_componentDefinition;
            if (implementation != null) {
                if (implementation instanceof Class) {
                    sb.append(((Class<?>) implementation).getName());
                } else {
                    // If the implementation instance does not override "toString", just display
                    // the class name, else display the component using its toString method
                    try {
                	Method m = implementation.getClass().getMethod("toString", new Class[0]);
                        if (m.getDeclaringClass().equals(Object.class)) {
                            sb.append(implementation.getClass().getName());
                        } else {
                            sb.append(implementation.toString());
                        }
                    }  catch (java.lang.NoSuchMethodException e) {
                        // Just display the class name
                        sb.append(implementation.getClass().getName());
                    }
                }
            } else {
                sb.append(super.toString());
            }
        }
        return sb.toString();
    }
    
    private void appendProperties(StringBuffer result) {
        Dictionary<Object, Object> properties = calculateServiceProperties();
        if (properties != null) {
            result.append("(");
            Enumeration<?> enumeration = properties.keys();
            while (enumeration.hasMoreElements()) {
                Object key = enumeration.nextElement();
                result.append(key.toString());
                result.append('=');
                Object value = properties.get(key);
                if (value instanceof String[]) {
                    String[] values = (String[]) value;
                    result.append('{');
                    for (int i = 0; i < values.length; i++) {
                        if (i > 0) {
                            result.append(',');
                        }
                        result.append(values[i].toString());
                    }
                    result.append('}');
                }
                else {
                    result.append(value.toString());
                }
                if (enumeration.hasMoreElements()) {
                    result.append(',');
                }
            }
            result.append(")");
        }
    }
    
    @Override
    public BundleContext getBundleContext() {
        return m_context;
    }
    
    @Override
    public Bundle getBundle() {
        return m_bundle;
    }

    public long getId() {
        return m_id;
    }
    
    public String getClassName() {
        Object serviceInstance = m_componentInstance;
        if (serviceInstance != null) {
            return serviceInstance.getClass().getName();
        } 
        
        Object implementation = m_componentDefinition;
        if (implementation != null) {
            if (implementation instanceof Class) {
                return ((Class<?>) implementation).getName();
            }
            return implementation.getClass().getName();
        } 
        
        Object instanceFactory = m_instanceFactory;
        if (instanceFactory != null) {
            return instanceFactory.getClass().getName();
        } else {
            // unexpected.
            return ComponentImpl.class.getName();
        }
    }
    
    public String[] getServices() {
        if (m_serviceName instanceof String[]) {
            return (String[]) m_serviceName;
        } else if (m_serviceName instanceof String) {
            return new String[] { (String) m_serviceName };
        } else {
            return null;
        }
    }
    
    public int getState() {
        return (isAvailable() ? ComponentDeclaration.STATE_REGISTERED : ComponentDeclaration.STATE_UNREGISTERED);
    }

    public void ensureNotActive() {
        if (m_active.get()) {
            throw new IllegalStateException("Can't modify an already started component.");
        }
    }
    
    public ComponentDeclaration getComponentDeclaration() {
        return this;
    }
    
    @Override
    public String toString() {
    	if (m_logger.getDebugKey() != null) {
    		return m_logger.getDebugKey();
    	}
    	return getClassName();
    }
    
    @Override
    public void setThreadPool(Executor threadPool) {
        ensureNotActive();
        m_executor = new DispatchExecutor(threadPool, m_logger);
    }
    
    @Override
    public Logger getLogger() {
        return m_logger;
    }

    @Override
    public Map<String, Long> getCallbacksTime() {
        return m_stopwatch;
    }
    
    private Executor getExecutor() {
        return m_executor;
    }
}