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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 - 2014 Board of Regents of the University of
 * Wisconsin-Madison, Broad Institute of MIT and Harvard, and Max Planck
 * Institute of Molecular Cell Biology and Genetics.
 * %%
 * 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
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 * #L%
 */

package org.scijava.service;

import org.scijava.Context;
import org.scijava.event.EventService;
import org.scijava.plugin.AbstractRichPlugin;

/**
 * Abstract superclass of {@link Service} implementations.
 * 
 * @author Curtis Rueden
 */
public abstract class AbstractService extends AbstractRichPlugin implements
	Service
{

	/**
	 * A pointer to the service's {@link Context}. Note that for two reasons, the
	 * context is not set in the superclass:
	 * 
	 * As services are initialized, their dependencies are recursively created
	 * and initialized too, which is something that normal context injection does
	 * not handle. I.e., the {@link Context#inject(Object)} method assumes the
	 * context and its associated services have all been initialized already.
	 * Event handler methods must not be registered until after service
	 * initialization is complete (i.e., during {@link #registerEventHandlers()},
	 * after {@link #initialize()}).
	 * 
	 */
	private Context context;

	// -- Service methods --

	@Override
	public void initialize() {
		// NB: Do nothing by default.
	}

	@Override
	public void registerEventHandlers() {
		// TODO: Consider removing this method in scijava-common 3.0.0.
		// Instead, the ServiceHelper could just invoke the lines below directly,
		// and there would be one less boilerplate Service method to implement.
		final EventService eventService = context().getService(EventService.class);
		if (eventService != null) eventService.subscribe(this);
	}

	// -- Contextual methods --

	@Override
	public Context getContext() {
		return context;
	}

	@Override
	public void setContext(final Context context) {
		// NB: Do not call super.setContext(Context)!
		// The ServiceHelper populates service parameters.
		// We do this because we need to recursively create and initialize
		// service dependencies, rather than merely injecting existing ones.
		this.context = context;
	}

	// -- Disposable methods --

	@Override
	public void dispose() {
		// NB: Do nothing by default.
	}

	// -- Object methods --

	@Override
	public String toString() {
		return getClass().getName() + " [priority = " + getPriority() + "]";
	}

}