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SciJava Common is a shared library for SciJava software. It provides a plugin framework, with an extensible mechanism for service discovery, backed by its own annotation processor, so that plugins can be loaded dynamically. It is used by downstream projects in the SciJava ecosystem, such as ImageJ and SCIFIO.

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/*
 * #%L
 * SciJava Common shared library for SciJava software.
 * %%
 * Copyright (C) 2009 - 2017 Board of Regents of the University of
 * Wisconsin-Madison, Broad Institute of MIT and Harvard, Max Planck
 * Institute of Molecular Cell Biology and Genetics, University of
 * Konstanz, and KNIME GmbH.
 * %%
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 * 
 * 1. Redistributions of source code must retain the above copyright notice,
 *    this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright notice,
 *    this list of conditions and the following disclaimer in the documentation
 *    and/or other materials provided with the distribution.
 * 
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDERS OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 * #L%
 */

package org.scijava.plugin;

import java.util.List;

import org.scijava.service.Service;

/**
 * A service for managing a particular sort of {@link SciJavaPlugin}.
 * 
 * There are many kinds of services, but most of them share one common
 * characteristic: they provide API specific to a particular type of plugin. A
 * few examples:
 * 
 * 
 * The {@link org.scijava.command.CommandService} works with
 * {@link org.scijava.command.Command}s.
 * The {@link org.scijava.text.TextService} works with
 * {@link org.scijava.text.TextFormat}s.
 * The {@link org.scijava.platform.PlatformService} works with
 * {@link org.scijava.platform.Platform}s.
 * 
 * 
 * Most services fit this pattern in one way or another. When you wish to
 * provide a new extensibility point, you create a new type of
 * {@link SciJavaPlugin}, and a corresponding {@link PTService} for working with
 * it. Depending on the nature of your new plugin type, this service might be:
 * 
 * 
 * A {@link SingletonService}, such as
 * {@link org.scijava.platform.PlatformService}, which manages
 * {@link SingletonPlugin}s.
 * A {@link HandlerService}, such as {@link org.scijava.text.TextService},
 * which manages {@link HandlerPlugin}s.
 * A {@link WrapperService}, such as
 * {@link org.scijava.widget.WidgetService}, which manages
 * {@link WrapperPlugin}s.
 * 
 * 
 * It is named {@code PTService} rather than {@code PluginTypeService} or
 * similar to avoid confusion with A) the {@link PluginService} itself, and B)
 * any other service interface intended to define the API of a concrete service.
 * In contrast to such services, the {@code PTService} is a more general layer
 * in a type hierarchy intended to ease creation of services that fit its
 * pattern.
 * 
 * 
 * @author Curtis Rueden
 * @param  Plugin type of the plugins being managed.
 * @see SingletonService
 * @see TypedService
 * @see WrapperService
 */
public interface PTService extends Service {

	/**
	 * Gets the service responsible for discovering and managing this service's
	 * plugins.
	 */
	default PluginService pluginService() {
		return context().getService(PluginService.class);
	}

	/** Gets the type of plugins managed by this service. */
	Class getPluginType();

	/** Gets the plugins managed by this service. */
	default List> getPlugins() {
		return pluginService().getPluginsOfType(getPluginType());
	}

	/** Creates an instance of the given plugin class. */
	default  P create(final Class pluginClass) {
		final PluginInfo info =
			pluginService().getPlugin(pluginClass, getPluginType());
		@SuppressWarnings("unchecked")
		final P plugin = (P) pluginService().createInstance(info);
		return plugin;
	}

	// -- Deprecated methods --

	/** @deprecated Use {@link #pluginService()} instead. */
	@Deprecated
	default PluginService getPluginService() {
		return pluginService();
	}
}