org.apache.sling.api.adapter.SlingAdaptable Maven / Gradle / Ivy
/*
* 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.sling.api.adapter;
import java.util.HashMap;
import java.util.Map;
/**
* The SlingAdaptable class is an (abstract) default implementation
* of the Adaptable interface. It just uses the default
* {@link AdapterManager} implemented to adapt itself to the requested type.
*
* Extensions of this class may overwrite the {@link #adaptTo(Class)} method
* using their own knowledge of adapters and should call this base class
* implementation to fall back for other types.
*
* @since 2.2 (Sling API Bundle 2.2.0)
*/
public abstract class SlingAdaptable implements Adaptable {
/** The adapter manager used for adapting the synthetic resource. */
private static volatile AdapterManager ADAPTER_MANAGER;
/**
* Sets the global {@link AdapterManager} to be used by this class.
*
* This method is intended to only be called by the {@link AdapterManager}
* wanting to register itself for use. Currently only a single adapter
* manager is supported by this class.
*
* @param adapterMgr The {@link AdapterManager} to be globally used.
*/
public static void setAdapterManager(final AdapterManager adapterMgr) {
ADAPTER_MANAGER = adapterMgr;
}
/**
* Unsets the global {@link AdapterManager}.
*
* This method is intended to only be called by the {@link AdapterManager}
* wanting to unregister itself. Currently only a single adapter manager is
* supported by this class.
*
* @param adapterMgr The {@link AdapterManager} to be unset. If this is not
* the same as currently registered this method has no effect.
*/
public static void unsetAdapterManager(final AdapterManager adapterMgr) {
if (ADAPTER_MANAGER == adapterMgr) {
ADAPTER_MANAGER = null;
}
}
/**
* Cached adapters per type.
*
* This map is created on demand by the {@link #adaptTo(Class)} method as a
* regular HashMap. This means, that extensions of this class
* are intended to be short-lived to not hold on to objects and classes for
* too long.
*/
private Map, Object> adaptersCache;
/**
* Calls into the registered {@link AdapterManager} to adapt this object to
* the desired type.
*
* This method implements a cache of adapters to improve performance. That
* is repeated calls to this method with the same class will result in the
* same object to be returned.
*
* @param The generic type to which this resource is adapted
* to
* @param type The Class object of the target type, such as
* javax.jcr.Node.class or
* java.io.File.class
* @return The adapter target or null if the resource cannot
* adapt to the requested type
*/
@SuppressWarnings("unchecked")
public AdapterType adaptTo(Class type) {
AdapterType result = null;
synchronized ( this ) {
if ( adaptersCache != null ) {
result = (AdapterType) adaptersCache.get(type);
}
if ( result == null ) {
final AdapterManager mgr = ADAPTER_MANAGER;
result = (mgr == null ? null : mgr.getAdapter(this, type));
if ( result != null ) {
if ( adaptersCache == null ) {
adaptersCache = new HashMap, Object>();
}
adaptersCache.put(type, result);
}
}
}
return result;
}
}