| /******************************************************************************* |
| * Copyright (c) 2001, 2008 Oracle 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: |
| * Oracle Corporation - initial API and implementation |
| *******************************************************************************/ |
| package org.eclipse.jst.jsf.common.internal.strategy; |
| |
| import java.util.Collections; |
| import java.util.HashMap; |
| import java.util.Iterator; |
| import java.util.LinkedHashMap; |
| import java.util.Map; |
| |
| import org.eclipse.jst.jsf.common.JSFCommonPlugin; |
| import org.eclipse.jst.jsf.common.internal.policy.IIteratorPolicy; |
| |
| /** |
| * A strategy composite that uses an iterator policy to provide the iterator |
| * used to decide what order to execute the strategy in. |
| * |
| * This composite represents a grouping of strategies which represent N ways |
| * to perform a particular calculation and which any number for those N ways |
| * may be applicable to any particular situation given the policy in place. |
| * |
| * By default, the first such strategy in policy order to provide the calculation |
| * wins and it's result is returned. You can modify the way the result is composed |
| * by providing your own composition strategy using the two-arg constructor. |
| * |
| * |
| * |
| * @author cbateman |
| * |
| * @param <INPUT> |
| * @param <OUTPUT> |
| * @param <RESULTTYPE> |
| * @param <IDTYPE> |
| * @param <STRATEGYTYPE> |
| */ |
| public abstract class IteratorPolicyBasedStrategyComposite<INPUT, OUTPUT, RESULTTYPE, IDTYPE, STRATEGYTYPE extends IIdentifiableStrategy<INPUT, OUTPUT, IDTYPE>> |
| extends StrategyComposite<INPUT, OUTPUT, RESULTTYPE, IDTYPE, STRATEGYTYPE> |
| { |
| private final Map<IDTYPE, STRATEGYTYPE> _strategies; |
| private IIteratorPolicy<IDTYPE> _policy; |
| private final Object _changeLock = new Object(); |
| |
| /** |
| * @param policy |
| */ |
| protected IteratorPolicyBasedStrategyComposite(final IIteratorPolicy<IDTYPE> policy) |
| { |
| super(); |
| _policy = policy; |
| _strategies = new LinkedHashMap<IDTYPE, STRATEGYTYPE>(); |
| } |
| |
| /** |
| * @param policy |
| * @param compositionStrategy |
| */ |
| protected IteratorPolicyBasedStrategyComposite(final IIteratorPolicy<IDTYPE> policy, AbstractCompositionStrategy<INPUT, OUTPUT, RESULTTYPE, STRATEGYTYPE> compositionStrategy) |
| { |
| super(compositionStrategy); |
| _policy = policy; |
| _strategies = new LinkedHashMap<IDTYPE, STRATEGYTYPE>(); |
| } |
| |
| /** |
| * Add strategy if not already present. |
| * |
| * @param strategy |
| */ |
| public final void addStrategy(final STRATEGYTYPE strategy) |
| { |
| synchronized(_changeLock) |
| { |
| _strategies.put(strategy.getId(), strategy); |
| } |
| } |
| |
| /** |
| * @param strategy |
| */ |
| public final void removeStrategy(final STRATEGYTYPE strategy) |
| { |
| synchronized(_changeLock) |
| { |
| _strategies.remove(strategy.getId()); |
| } |
| } |
| |
| /** |
| * Change the active policy used to select the order in which the composite |
| * calls it's child strategies. |
| * |
| * If the policy is not set, then strategies are called in |
| * |
| * @param policy |
| */ |
| public final void setPolicy(final IIteratorPolicy<IDTYPE> policy) |
| { |
| // policy may not be null |
| if (policy == null) |
| { |
| JSFCommonPlugin.log(new Exception("stack trace only"), "Policy can't be null"); //$NON-NLS-1$ //$NON-NLS-2$ |
| return; |
| } |
| |
| // protect access in case getIterator is being called simulataneously |
| synchronized(_changeLock) |
| { |
| _policy = policy; |
| } |
| } |
| |
| @Override |
| public final Iterator<STRATEGYTYPE> getIterator() |
| { |
| IIteratorPolicy<IDTYPE> policy = null; |
| Map<IDTYPE, STRATEGYTYPE> strategies = Collections.emptyMap(); |
| |
| synchronized(_changeLock) |
| { |
| policy = _policy; |
| strategies = Collections.unmodifiableMap(new HashMap<IDTYPE, STRATEGYTYPE>(_strategies)); |
| } |
| |
| final Iterator<IDTYPE> iterator = policy.getIterator(strategies.keySet()); |
| return new StrategyIterator<IDTYPE, STRATEGYTYPE>(strategies, iterator); |
| } |
| |
| @Override |
| public abstract RESULTTYPE getNoResult(); |
| |
| private static class StrategyIterator<IDTYPE, STRATEGYTYPE> implements |
| Iterator<STRATEGYTYPE> |
| { |
| private final Map<IDTYPE, STRATEGYTYPE> _map; |
| private final Iterator<IDTYPE> _policyIterator; |
| |
| private StrategyIterator(final Map<IDTYPE, STRATEGYTYPE> map, |
| final Iterator<IDTYPE> policyIterator) |
| { |
| _map = map; |
| _policyIterator = policyIterator; |
| } |
| |
| public boolean hasNext() |
| { |
| return _policyIterator.hasNext(); |
| } |
| |
| public STRATEGYTYPE next() |
| { |
| IDTYPE id = _policyIterator.next(); |
| return _map.get(id); |
| } |
| |
| public void remove() |
| { |
| throw new UnsupportedOperationException(); |
| } |
| } |
| } |