| /****************************************************************************** |
| * Copyright (c) 2002, 2006 IBM Corporation and others. |
| * All rights reserved. This program and the accompanying materials |
| * are made available under the terms of the Eclipse Public License v1.0 |
| * which accompanies this distribution, and is available at |
| * http://www.eclipse.org/legal/epl-v10.html |
| * |
| * Contributors: |
| * IBM Corporation - initial API and implementation |
| ****************************************************************************/ |
| |
| package org.eclipse.gmf.runtime.common.core.service; |
| |
| import java.util.ArrayList; |
| import java.util.Arrays; |
| import java.util.Collections; |
| import java.util.List; |
| |
| import org.eclipse.gmf.runtime.common.core.service.Service.ProviderDescriptor; |
| import org.eclipse.gmf.runtime.common.core.util.EnumeratedType; |
| |
| /** |
| * An enumeration of provider execution strategies. |
| * <P> |
| * Each service provider has a <code>ProviderPriority</code> that is declared |
| * in its extension descriptor. It is the |
| * {@link org.eclipse.gmf.runtime.common.core.service.ExecutionStrategy} that |
| * determines how service provider priorities are used to select a provider to |
| * service each client request. For example, if the |
| * {@link org.eclipse.gmf.runtime.common.core.service.ExecutionStrategy#FIRST} |
| * is used, the provider with the highest priority will give an answer to the |
| * request. |
| * |
| * @see org.eclipse.gmf.runtime.common.core.service |
| * |
| * @author khussey |
| * @canBeSeenBy %partners |
| */ |
| public abstract class ExecutionStrategy extends EnumeratedType { |
| |
| /** |
| * The list of pre-defined provider priorities. |
| */ |
| public static final ProviderPriority[] PRIORITIES = |
| { |
| ProviderPriority.HIGHEST, |
| ProviderPriority.HIGH, |
| ProviderPriority.MEDIUM, |
| ProviderPriority.LOW, |
| ProviderPriority.LOWEST }; |
| |
| /** |
| * An internal unique identifier for provider execution strategies. |
| */ |
| private static int nextOrdinal = 0; |
| |
| /** |
| * Executes an operation on the first provider of the highest priority |
| * that provides the operation. |
| */ |
| public static final ExecutionStrategy FIRST = |
| new ExecutionStrategy("First") { //$NON-NLS-1$ |
| |
| private static final long serialVersionUID = 1L; |
| |
| public List execute(Service service, IOperation operation) { |
| for (int i = 0; i < PRIORITIES.length; ++i) { |
| List providers = service.getProviders(this, PRIORITIES[i], operation); |
| |
| if (providers.size() != 0) { |
| return Collections.singletonList(operation.execute((IProvider) providers.get(0))); |
| } |
| } |
| |
| return Collections.EMPTY_LIST; |
| } |
| |
| public List getUncachedProviders( |
| Service service, |
| ProviderPriority priority, |
| IOperation operation) { |
| |
| List descriptors = service.getProviders(priority); |
| int size = descriptors.size(); |
| |
| for (int i = 0; i < size; ++i) { |
| ProviderDescriptor descriptor = (ProviderDescriptor)descriptors.get(i); |
| |
| if (Service.safeProvides(descriptor, operation)) { |
| return Collections.singletonList(descriptor.getProvider()); |
| } |
| } |
| |
| return Collections.EMPTY_LIST; |
| } |
| }; |
| |
| /** |
| * Executes an operation on the last provider of the lowest priority |
| * that provides the operation. |
| */ |
| public static final ExecutionStrategy LAST = |
| new ExecutionStrategy("Last") { //$NON-NLS-1$ |
| |
| private static final long serialVersionUID = 1L; |
| |
| public List execute(Service service, IOperation operation) { |
| for (int i = PRIORITIES.length; --i >= 0;) { |
| List providers = service.getProviders(this, PRIORITIES[i], operation); |
| int size = providers.size(); |
| |
| if (size != 0) { |
| return Collections.singletonList( |
| operation.execute( |
| (IProvider) providers.get(size - 1))); |
| } |
| } |
| |
| return Collections.EMPTY_LIST; |
| } |
| |
| public List getUncachedProviders( |
| Service service, |
| ProviderPriority priority, |
| IOperation operation) { |
| |
| List descriptors = service.getProviders(priority); |
| |
| for (int i = descriptors.size(); --i >= 0;) { |
| ProviderDescriptor descriptor = (ProviderDescriptor)descriptors.get(i); |
| |
| if (Service.safeProvides(descriptor, operation)) { |
| return Collections.singletonList(descriptor.getProvider()); |
| } |
| } |
| |
| return Collections.EMPTY_LIST; |
| } |
| }; |
| |
| /** |
| * Executes an operation on all providers that provide the operation, in |
| * order from highest to lowest priority. |
| */ |
| public static final ExecutionStrategy FORWARD = |
| new ExecutionStrategy("Forward") { //$NON-NLS-1$ |
| |
| private static final long serialVersionUID = 1L; |
| |
| public List execute(Service service, IOperation operation) { |
| List results = new ArrayList(); |
| |
| for (int i = 0; i < PRIORITIES.length; ++i) { |
| List providers = service.getProviders(this, PRIORITIES[i], operation); |
| int size = providers.size(); |
| |
| for (int j = 0; j < size; ++j) { |
| results.add(operation.execute((IProvider) providers.get(j))); |
| } |
| } |
| |
| return results; |
| } |
| }; |
| |
| /** |
| * Executes an operation on all providers that provide the operation, in |
| * reverse order from lowest to highest priority. |
| */ |
| public static final ExecutionStrategy REVERSE = |
| new ExecutionStrategy("Reverse") { //$NON-NLS-1$ |
| |
| private static final long serialVersionUID = 1L; |
| |
| public List execute(Service service, IOperation operation) { |
| List results = new ArrayList(); |
| |
| for (int i = PRIORITIES.length; --i >= 0;) { |
| List providers = service.getProviders(this, PRIORITIES[i], operation); |
| |
| for (int j = providers.size(); --j >= 0;) { |
| results.add(operation.execute((IProvider) providers.get(j))); |
| } |
| } |
| |
| return results; |
| } |
| }; |
| |
| /** |
| * The list of values for this enumerated type. |
| */ |
| private static final ExecutionStrategy[] VALUES = |
| { FIRST, LAST, FORWARD, REVERSE }; |
| |
| /** |
| * Constructs a new execution strategy with the specified name. |
| * |
| * @param name The name of the new execution strategy. |
| */ |
| protected ExecutionStrategy(String name) { |
| super(name, nextOrdinal++); |
| } |
| |
| /** |
| * Constructs a new execution strategy with the specified name and ordinal. |
| * |
| * @param name The name of the new execution strategy. |
| * @param ordinal The ordinal for the new execution strategy. |
| */ |
| protected ExecutionStrategy(String name, int ordinal) { |
| super(name, ordinal); |
| } |
| |
| /** |
| * Retrieves the list of constants for this enumerated type. |
| * |
| * @return The list of constants for this enumerated type. |
| */ |
| protected List getValues() { |
| return Collections.unmodifiableList(Arrays.asList(VALUES)); |
| } |
| |
| /** |
| * Executes the specified operation on providers obtained from the |
| * specified service, according to this execution strategy. |
| * |
| * @param service The service from which to obtain the providers. |
| * @param operation The operation to be executed. |
| * @return The list of results. |
| */ |
| public abstract List execute(Service service, IOperation operation); |
| |
| /** |
| * Retrieves a list of providers of the specified priority that provide the |
| * specified operation. |
| * |
| * @param service The service used by the strategy |
| * @param priority The priority of providers to be retrieved. |
| * @param operation The operation that the provides must provide. |
| * @return A list of uncached providers. |
| */ |
| public List getUncachedProviders( |
| Service service, |
| ProviderPriority priority, |
| IOperation operation) { |
| |
| List descriptors = service.getProviders(priority); |
| int size = descriptors.size(); |
| List providers = new ArrayList(size); |
| |
| for (int i = 0; i < size; ++i) { |
| ProviderDescriptor descriptor = (ProviderDescriptor)descriptors.get(i); |
| |
| if (Service.safeProvides(descriptor, operation)) { |
| providers.add(descriptor.getProvider()); |
| } |
| } |
| |
| return providers; |
| } |
| |
| /** |
| * Retrieves a list of providers of the specified priority. |
| * |
| * @param service The service used by the strategy |
| * @param priority The priority of providers to be retrieved. |
| * @return A list of providers of the specified priority. |
| */ |
| protected final List getProviders(Service service, ProviderPriority priority) { |
| return service.getProviders(priority); |
| } |
| |
| /** |
| * Retrieves a list of providers of the specified priority that provide the |
| * specified operation. If this service is optimized, the result will be |
| * cached the first time it is retrieved. If caching is pessimistic, the |
| * providers from the cache will be checked first. |
| * |
| * @param service The service used by the strategy |
| * @param strategy The strategy used by the service |
| * @param priority The priority of providers to be retrieved. |
| * @param operation The operation that the provides must provide. |
| * @return A list of providers (from the cache, if appropriate). |
| */ |
| protected final List getProviders( |
| Service service, |
| ExecutionStrategy strategy, |
| ProviderPriority priority, |
| IOperation operation) { |
| return service.getProviders(strategy, priority, operation); |
| } |
| } |