DefaultResourceHandler.java

/*
 * Copyright 2017 OmniFaces
 *
 * 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.omnifaces.resourcehandler;

import javax.faces.application.Resource;
import javax.faces.application.ResourceHandler;
import javax.faces.application.ResourceHandlerWrapper;

/**
 * <p>
 * A default {@link ResourceHandler} implementation which hooks on all three {@link #createResource(String)},
 * {@link #createResource(String, String)} and {@link #createResource(String, String, String)} methods. Implementors
 * should only need to override <strong>either</strong> {@link #getLibraryName()} and
 * {@link #createResourceFromLibrary(String, String)}, <strong>or</strong> {@link #decorateResource(Resource)}.
 *
 * @author Bauke Scholtz
 * @since 2.0
 */
public abstract class DefaultResourceHandler extends ResourceHandlerWrapper {

	// Constants ------------------------------------------------------------------------------------------------------

	public static final String RES_NOT_FOUND = "RES_NOT_FOUND";

	// Properties -----------------------------------------------------------------------------------------------------

	private ResourceHandler wrapped;

	// Constructors ---------------------------------------------------------------------------------------------------

	/**
	 * Creates a new instance of this default resource handler which wraps the given resource handler.
	 * @param wrapped The resource handler to be wrapped.
	 */
	public DefaultResourceHandler(ResourceHandler wrapped) {
		this.wrapped = wrapped;
	}

	// Actions --------------------------------------------------------------------------------------------------------

	/**
	 * Delegate to {@link #decorateResource(Resource, String, String)} with result of {@link #createResource(String)}
	 * from the wrapped resource handler.
	 * <p>
	 * Implementors should <strong>not</strong> override this.
	 */
	@Override
	public Resource createResource(String resourceName) {
		return decorateResource(getWrapped().createResource(resourceName), resourceName, null);
	}

	/**
	 * If library name is not null and it equals {@link #getLibraryName()}, then delegate to
	 * {@link #createResourceFromLibrary(String, String)} with <code>null</code> as content type, else delegate to
	 * {@link #decorateResource(Resource, String, String)} with result of {@link #createResource(String, String)}
	 * from the wrapped resource handler.
	 * <p>
	 * Implementors should <strong>not</strong> override this.
	 */
	@Override
	public Resource createResource(String resourceName, String libraryName) {
		if (libraryName != null && libraryName.equals(getLibraryName())) {
			return createResourceFromLibrary(resourceName, null);
		}
		else {
			return decorateResource(getWrapped().createResource(resourceName, libraryName), resourceName, libraryName);
		}
	}

	/**
	 * If library name is not null and it equals {@link #getLibraryName()}, then delegate to
	 * {@link #createResourceFromLibrary(String, String)}, else delegate to
	 * {@link #decorateResource(Resource, String, String)} with result of
	 * {@link #createResource(String, String, String)} from the wrapped resource handler.
	 * <p>
	 * Implementors should <strong>not</strong> override this.
	 */
	@Override
	public Resource createResource(String resourceName, String libraryName, String contentType) {
		if (libraryName != null && libraryName.equals(getLibraryName())) {
			return createResourceFromLibrary(resourceName, contentType);
		}
		else {
			return decorateResource(getWrapped().createResource(resourceName, libraryName, contentType), resourceName, libraryName);
		}
	}

	/**
	 * Returns the library name on which this resource handler implementation should listen. If a resource from
	 * specifically this library name is requested, then {@link #createResourceFromLibrary(String, String)} will be
	 * called to create the resource, else {@link #decorateResource(Resource)} will be called with result of the call
	 * from the wrapped resource handler.
	 * <p>
	 * The default implementation returns <code>null</code>.
	 * @return The library name on which this resource handler implementation should listen.
	 */
	public String getLibraryName() {
		return null;
	}

	/**
	 * Returns the library-specific resource in case a resource from specifically the library name as identified by
	 * {@link #getLibraryName()} is requested.
	 * <p>
	 * The default implementation returns <code>null</code>.
	 * @param resourceName The resource name.
	 * @param contentType The content type.
	 * @return The library-specific resource.
	 */
	public Resource createResourceFromLibrary(String resourceName, String contentType) {
		return null;
	}

	/**
	 * Decorate the given resource. This will only be called if no library-specific resource has been requested.
	 * <p>
	 * The default implementation delegates to {@link #decorateResource(Resource)}.
	 * @param resource The resource to be decorated.
	 * @param resourceName The resource name.
	 * @param libraryName The library name.
	 * @return The decorated resource.
	 * @since 2.6
	 */
	public Resource decorateResource(Resource resource, String resourceName, String libraryName) {
		return decorateResource(resource);
	}

	/**
	 * Decorate the given resource. This will only be called if no library-specific resource has been requested.
	 * <p>
	 * The default implementation just returns the given resource unmodified.
	 * @param resource The resource to be decorated.
	 * @return The decorated resource.
	 */
	public Resource decorateResource(Resource resource) {
		return resource;
	}

	@Override
	public ResourceHandler getWrapped() {
		return wrapped;
	}

}