Java tutorial
/* AWE - Amanzi Wireless Explorer * http://awe.amanzi.org * (C) 2008-2009, AmanziTel AB * * This library is provided under the terms of the Eclipse Public License * as described at http://www.eclipse.org/legal/epl-v10.html. Any use, * reproduction or distribution of the library constitutes recipient's * acceptance of this agreement. * * This library is distributed WITHOUT ANY WARRANTY; without even the * implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. */ package org.amanzi.neo.providers.context; import java.lang.reflect.Constructor; import java.lang.reflect.InvocationTargetException; import java.util.ArrayList; import java.util.HashMap; import java.util.List; import java.util.Map; import java.util.Map.Entry; import org.amanzi.neo.db.manager.DatabaseManagerFactory; import org.amanzi.neo.nodeproperties.INodeProperties; import org.amanzi.neo.providers.ContextException; import org.amanzi.neo.providers.IProviderContext; import org.amanzi.neo.providers.internal.IModelProvider; import org.amanzi.neo.services.IService; import org.apache.commons.lang3.StringUtils; import org.eclipse.core.runtime.CoreException; import org.eclipse.core.runtime.IConfigurationElement; import org.eclipse.core.runtime.IExtensionRegistry; import org.eclipse.core.runtime.Platform; import org.neo4j.graphdb.GraphDatabaseService; /** * TODO Purpose of * <p> * </p> * * @author Nikolay Lagutko (nikolay.lagutko@amanzitel.com) * @since 1.0.0 */ public class ProviderContextImpl implements IProviderContext { private static final String NODE_PROPERTIES_EXTENSION_POINT = "org.amanzi.nodeproperties"; private static final String SERVICES_EXTENSION_POINT = "org.amanzi.services"; private static final String PROVIDERS_EXTENSION_POINT = "org.amanzi.providers"; private static final String ID_ATTRIBUTE = "id"; private static final String CLASS_ATTRIBUTE = "class"; private static final String PARAMETERS_TAG = "parameters"; private static final String SERVICE_REFERENCE = "serviceReference"; private static final String NODE_PROPERTIES_REFERENCE = "nodePropertiesReference"; private static final String PROVIDER_REFERENCES = "providerReference"; private static final String REFERENCE_ATTRIBUTE = "refId"; private final Map<String, IModelProvider<?>> providersCache = new HashMap<String, IModelProvider<?>>(); private final Map<String, IService> servicesCache = new HashMap<String, IService>(); private final Map<String, INodeProperties> nodePropertiesCache = new HashMap<String, INodeProperties>(); private final IExtensionRegistry registry; private List<String> serviceStack; private List<String> providerStack; public ProviderContextImpl() { registry = Platform.getExtensionRegistry(); } protected ProviderContextImpl(final IExtensionRegistry registry) { this.registry = registry; } @SuppressWarnings("unchecked") @Override public synchronized <T extends IModelProvider<?>> T get(final String id) throws ContextException { T result = (T) providersCache.get(id); if (result == null) { result = (T) createModelProvider(id); providersCache.put(id, result); } return result; } @SuppressWarnings("unchecked") @Override public synchronized <T extends INodeProperties> T getProperties(final String id) throws ContextException { try { return (T) getNodeProperties(id); } catch (CoreException e) { return null; } } protected IService getService(final String id) throws ContextException { assert !StringUtils.isEmpty(id); IService result = servicesCache.get(id); if (result == null) { result = createService(id); servicesCache.put(id, result); } return result; } protected INodeProperties getNodeProperties(final String id) throws CoreException, ContextException { assert !StringUtils.isEmpty(id); INodeProperties result = nodePropertiesCache.get(id); if (result == null) { result = createNodeProperties(id); nodePropertiesCache.put(id, result); } return result; } protected IModelProvider<?> createModelProvider(final String id) throws ContextException { assert !StringUtils.isEmpty(id); if (providerStack == null) { providerStack = new ArrayList<String>(); } if (providerStack.contains(id)) { String message = "A cycle was detected <" + providerStack + ">"; providerStack = null; throw new ContextException(message); } providerStack.add(id); IConfigurationElement element = findConfigurationElement(PROVIDERS_EXTENSION_POINT, id); if (element == null) { throw new ContextException("ModelProvider <" + id + "> was not found in context"); } try { return (IModelProvider<?>) createInstance(element, false); } catch (Exception e) { throw new ContextException(e); } finally { if (providerStack != null) { providerStack.remove(id); } } } protected IService createService(final String id) throws ContextException { assert !StringUtils.isEmpty(id); if (serviceStack == null) { serviceStack = new ArrayList<String>(); } if (serviceStack.contains(id)) { String message = "A cycle was detected <" + serviceStack + ">"; serviceStack = null; throw new ContextException(message); } serviceStack.add(id); IConfigurationElement element = findConfigurationElement(SERVICES_EXTENSION_POINT, id); if (element == null) { throw new ContextException("Service <" + id + "> was not found in context"); } try { return (IService) createInstance(element, true); } catch (Exception e) { throw new ContextException(e); } finally { if (serviceStack != null) { serviceStack.remove(id); } } } protected INodeProperties createNodeProperties(final String id) throws CoreException, ContextException { assert !StringUtils.isEmpty(id); IConfigurationElement element = findConfigurationElement(NODE_PROPERTIES_EXTENSION_POINT, id); if (element != null) { try { INodeProperties result = (INodeProperties) element.createExecutableExtension(CLASS_ATTRIBUTE); return result; } catch (ClassCastException e) { throw new ContextException(e); } } throw new ContextException("NodeProperties <" + id + "> was not found in context"); } private IConfigurationElement findConfigurationElement(final String extensionPoint, final String id) { IConfigurationElement result = null; IConfigurationElement[] nodePropertiesElements = registry.getConfigurationElementsFor(extensionPoint); for (IConfigurationElement singleElement : nodePropertiesElements) { if (singleElement.getAttribute(ID_ATTRIBUTE).equals(id)) { result = singleElement; break; } } return result; } @SuppressWarnings("unchecked") protected <T> T createInstance(final IConfigurationElement configElement, final boolean isService) throws ClassNotFoundException, NoSuchMethodException, CoreException, ContextException, InvocationTargetException, IllegalAccessException, InstantiationException { String className = configElement.getAttribute(CLASS_ATTRIBUTE); Class<? extends T> clazz = (Class<? extends T>) Class.forName(className); IConfigurationElement[] parametersBlock = configElement.getChildren(PARAMETERS_TAG); return createInstance(clazz, parametersBlock, isService); } protected <T> T createInstance(final Class<? extends T> clazz, final IConfigurationElement[] parameterBlock, final boolean isService) throws ContextException, CoreException, InvocationTargetException, IllegalAccessException, InstantiationException { // should be 0 or 1 element assert parameterBlock != null; assert parameterBlock.length < 2; IConfigurationElement singleParameterBlock = null; if (parameterBlock.length == 1) { singleParameterBlock = parameterBlock[0]; } return createInstance(clazz, singleParameterBlock, isService); } protected <T> T createInstance(final Class<? extends T> clazz, final IConfigurationElement parameterBlock, final boolean isService) throws ContextException, CoreException, InvocationTargetException, IllegalAccessException, InstantiationException { Map<Class<? extends Object>, Object> parametersMap = new HashMap<Class<? extends Object>, Object>(); if (isService) { initializeWithDatabaseService(parametersMap); } if (parameterBlock != null) { for (IConfigurationElement parameter : parameterBlock.getChildren()) { String name = parameter.getName(); String reference = parameter.getAttribute(REFERENCE_ATTRIBUTE); Object parameterInstance = null; if (name.equals(SERVICE_REFERENCE)) { parameterInstance = getService(reference); } else if (name.equals(NODE_PROPERTIES_REFERENCE)) { parameterInstance = getNodeProperties(reference); } else if (name.equals(PROVIDER_REFERENCES)) { parameterInstance = get(reference); } else { throw new ContextException("Unknown parameter <" + name + ">"); } parametersMap.put(parameterInstance.getClass(), parameterInstance); } } return createInstance(clazz, parametersMap); } @SuppressWarnings("unchecked") protected <T> T createInstance(final Class<? extends T> clazz, final Map<Class<? extends Object>, Object> parametersMap) throws InvocationTargetException, IllegalAccessException, InstantiationException, ContextException { Constructor<?> correctConstructor = null; Object[] arguments = null; for (Constructor<?> constructor : clazz.getConstructors()) { Class<?>[] parameterTypes = constructor.getParameterTypes(); arguments = new Object[parameterTypes.length]; int i = 0; if (parameterTypes.length == parametersMap.size()) { boolean isFound = false; for (Class<?> argumentType : parameterTypes) { for (Entry<Class<? extends Object>, Object> parameterEntry : parametersMap.entrySet()) { Class<?> parameterClass = parameterEntry.getKey(); if (argumentType.isAssignableFrom(parameterClass)) { isFound = true; arguments[i++] = parameterEntry.getValue(); break; } } if (!isFound) { break; } } if (isFound) { correctConstructor = constructor; } } } if (correctConstructor == null) { throw new ContextException("Unable to create <" + clazz.getSimpleName() + ">. Constructor for Parameters <" + parametersMap.keySet() + "> not found."); } return (T) correctConstructor.newInstance(arguments); } private void initializeWithDatabaseService(final Map<Class<? extends Object>, Object> parametersMap) { GraphDatabaseService databaseService = DatabaseManagerFactory.getDatabaseManager().getDatabaseService(); parametersMap.put(GraphDatabaseService.class, databaseService); } }