// Copyright 2006, 2007 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.tapestry.ioc.util;
import static org.apache.tapestry.ioc.internal.util.CollectionFactory.*;
import org.apache.tapestry.ioc.internal.util.InheritanceSearch;
import java.util.List;
import java.util.Map;
/**
* A key component in implementing the "Gang of Four" Strategy pattern. A StrategyRegistry will
* match up a given input type with a registered strategy for that type.
*
* @param <A>
* the type of the strategy adapter
*/
public final class StrategyRegistry<A>
{
private final Class<A> _adapterType;
private final Map<Class, A> _registrations = newMap();
private final Map<Class, A> _cache = newConcurrentMap();
/**
* Creates a strategy registry for the given adapter type.
*
* @param adapterType the type of adapter retrieved from the registry
* @param registrations map of registrations (the contents of the map are copied)
*/
public StrategyRegistry(final Class<A> adapterType, Map<Class, A> registrations)
{
_adapterType = adapterType;
_registrations.putAll(registrations);
}
public static <A> StrategyRegistry<A> newInstance(Class<A> adapterType,
Map<Class, A> registrations)
{
return new StrategyRegistry<A>(adapterType, registrations);
}
public void clearCache()
{
_cache.clear();
}
public Class<A> getAdapterType()
{
return _adapterType;
}
/**
* Gets an adapter for an object. Searches based on the value's class, unless the value is null,
* in which case, a search on class void is used.
*
* @param value for which an adapter is needed
* @return the adaptoer for the value
* @throws IllegalArgumentException if no matching adapter may be found
*/
public A getByInstance(Object value)
{
return get(value == null ? void.class : value.getClass());
}
/**
* Searches for an adapter corresponding to the given input type.
*
* @param type the type to search
* @return the corresponding adapter
* @throws IllegalArgumentException if no matching adapter may be found
*/
public A get(Class type)
{
A result = _cache.get(type);
if (result == null)
{
result = findMatch(type);
_cache.put(type, result);
}
return result;
}
private A findMatch(Class type)
{
for (Class t : new InheritanceSearch(type))
{
A result = _registrations.get(t);
if (result != null) return result;
}
// Report the error. These things really confused the hell out of people in Tap4, so we're
// going the extra mile on the exception message.
List<String> names = newList();
for (Class t : _registrations.keySet())
names.add(t.getName());
throw new IllegalArgumentException(UtilMessages
.noStrategyAdapter(type, _adapterType, names));
}
@Override
public String toString()
{
return String.format("StrategyRegistry[%s]", _adapterType.getName());
}
}