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Wicket is a Java web application framework that takes simplicity, separation of concerns and ease of development to a whole new level. Wicket pages can be mocked up, previewed and later revised using standard WYSIWYG HTML design tools. Dynamic content processing and form handling is all handled in Java code using a first-class component model backed by POJO data beans that can easily be persisted using your favorite technology.

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/*
 * 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.wicket;

import java.util.Locale;

import org.apache.wicket.request.resource.IResource;
import org.apache.wicket.request.resource.ResourceReference;
import org.apache.wicket.request.resource.ResourceReference.Key;
import org.apache.wicket.request.resource.ResourceReferenceRegistry;
import org.apache.wicket.util.lang.Args;

/**
 * Class which holds shared resources. Resources can be shared by name. An optional scope can be
 * given to prevent naming conflicts and a locale and/or style can be given as well.
 * 
 * 
 * Unlike component hosted resources, shared resources have stable URLs, which makes them suitable
 * for indexing by web crawlers and caching by web browsers. As they are also not synchronised on
 * the {@link Session}, they can be loaded asynchronously, which is important with images and
 * resources such as JavaScript and CSS.
 */
public class SharedResources
{
	private final ResourceReferenceRegistry registry;

	/**
	 * Construct.
	 * 
	 * @param registry
	 */
	public SharedResources(ResourceReferenceRegistry registry)
	{
		this.registry = Args.notNull(registry, "registry");
	}

	/**
	 * A {@link ResourceReference} that is used to register a reference to a known {@link IResource}
	 */
	private static final class AutoResourceReference extends ResourceReference
	{
		private static final long serialVersionUID = 1L;

		private final IResource resource;

		private AutoResourceReference(Class scope, String name, Locale locale, String style,
			String variation, IResource resource)
		{
			super(scope, name, locale, style, variation);
			this.resource = resource;
		}

		@Override
		public IResource getResource()
		{
			return resource;
		}
	}

	/**
	 * Adds a resource.
	 * 
	 * @param scope
	 *            Scope of resource
	 * @param name
	 *            Logical name of resource
	 * @param locale
	 *            The locale of the resource
	 * @param style
	 *            The resource style (see {@link org.apache.wicket.Session})
	 * @param variation
	 *            The component specific variation of the style
	 * @param resource
	 *            Resource to store
	 */
	public final void add(final Class scope, final String name, final Locale locale,
		final String style, final String variation, final IResource resource)
	{
		ResourceReference ref = new AutoResourceReference(scope, name, locale, style, variation,
			resource);
		registry.registerResourceReference(ref);
	}

	/**
	 * Adds a resource.
	 * 
	 * @param name
	 *            Logical name of resource
	 * @param locale
	 *            The locale of the resource
	 * @param resource
	 *            Resource to store
	 */
	public final void add(final String name, final Locale locale, final IResource resource)
	{
		add(Application.class, name, locale, null, null, resource);
	}

	/**
	 * Adds a resource.
	 * 
	 * @param name
	 *            Logical name of resource
	 * @param resource
	 *            Resource to store
	 */
	public final void add(final String name, final IResource resource)
	{
		add(Application.class, name, null, null, null, resource);
	}

	/**
	 * Resolves a {@link ResourceReference} for a shared resource by using
	 * {@link org.apache.wicket.Application} as a scope and {@code null} for
	 * locale, style and variation.
	 *
	 * @param name
	 *            Logical name of resource
	 */
	public final ResourceReference get(String name)
	{
		return get(Application.class, name, null, null, null, false);
	}

	/**
	 * Resolves a {@link ResourceReference} for a shared resource.
	 * 
	 * @param scope
	 *            Scope of resource
	 * @param name
	 *            Logical name of resource
	 * @param locale
	 *            The locale of the resource
	 * @param style
	 *            The resource style (see {@link org.apache.wicket.Session})
	 * @param variation
	 *            The component specific variation of the style
	 * @param strict
	 *            If true, "weaker" combination of scope, name, locale etc. are not tested
	 * @return Either the resource reference found in the registry or, if requested, a resource
	 *         reference automatically created based on the parameters provided. The automatically
	 *         created resource reference will automatically be added to the registry.
	 */
	public ResourceReference get(Class scope, String name, Locale locale, String style,
		String variation, boolean strict)
	{
		return registry.getResourceReference(scope, name, locale, style, variation, strict, true);
	}

	/**
	 * Removes a resource.
	 * 
	 * @param key
	 *            the resource reference's identifier
	 * @return the removed {@link ResourceReference}. {@code null} if there was no registration for
	 *         this {@link Key}
	 */
	public final ResourceReference remove(final Key key)
	{
		return registry.unregisterResourceReference(key);
	}
}