org.scijava.plugin.DefaultPluginFinder Maven / Gradle / Ivy

Show more of this group Show more artifacts with this name
Show all versions of scijava-common Show documentation

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.

There is a newer version: 2.99.0

Show newest version

/*
 * #%L
 * SciJava Common shared library for SciJava software.
 * %%
 * Copyright (C) 2009 - 2016 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
 * 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.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.regex.Pattern;
import java.util.regex.PatternSyntaxException;

import org.scijava.annotations.Index;
import org.scijava.annotations.IndexItem;

/**
 * Default SciJava plugin discovery mechanism.
 * 
 * It works by scanning the classpath for {@link Plugin} annotations
 * previously indexed by scijava-common itself.
 * 
 * 
 * @author Curtis Rueden
 */
public class DefaultPluginFinder implements PluginFinder {

	/** Class loader to use when querying the annotation indexes. */
	private final ClassLoader customClassLoader;

	private final PluginBlacklist blacklist;

	// -- Constructors --

	public DefaultPluginFinder() {
		this(null);
	}

	public DefaultPluginFinder(final ClassLoader classLoader) {
		customClassLoader = classLoader;
		blacklist = new SysPropBlacklist();
	}

	// -- PluginFinder methods --

	@Override
	public HashMap findPlugins(
		final List> plugins)
	{
		final HashMap exceptions =
			new HashMap<>();

		// load the annotation indexes
		final ClassLoader classLoader = getClassLoader();
		final Index annotationIndex =
			Index.load(Plugin.class, classLoader);

		// create a PluginInfo object for each item in the index
		for (final IndexItem item : annotationIndex) {
			if (blacklist.contains(item.className())) continue;
			try {
				final PluginInfo info = createInfo(item, classLoader);
				plugins.add(info);
			}
			catch (final Throwable t) {
				exceptions.put(item.className(), t);
			}
		}

		return exceptions;
	}

	// -- Helper methods --

	private PluginInfo createInfo(
		final IndexItem item, final ClassLoader classLoader)
	{
		final String className = item.className();
		final Plugin plugin = item.annotation();

		@SuppressWarnings("unchecked")
		final Class pluginType =
			(Class) plugin.type();

		return new PluginInfo<>(className, pluginType, plugin, classLoader);
	}

	private ClassLoader getClassLoader() {
		if (customClassLoader != null) return customClassLoader;
		return Thread.currentThread().getContextClassLoader();
	}

	// -- Helper classes --

	private interface PluginBlacklist {
		boolean contains(String className);
	}

	/**
	 * A blacklist defined by the {@code scijava.plugin.blacklist} system
	 * property, formatted as a colon-separated list of regexes.
	 * 
	 * If a plugin class matches any of the regexes, it is excluded from the
	 * plugin index.
	 * 
	 */
	private class SysPropBlacklist implements PluginBlacklist {
		private final List patterns;

		public SysPropBlacklist() {
			final String sysProp = System.getProperty("scijava.plugin.blacklist");
			final String[] regexes = //
				sysProp == null ? new String[0] : sysProp.split(":");
			patterns = new ArrayList<>(regexes.length);
			for (final String regex : regexes) {
				try {
					patterns.add(Pattern.compile(regex));
				}
				catch (final PatternSyntaxException exc) {
					// NB: Ignore this malformed pattern.
				}
			}
		}

		// -- PluginBlacklist methods --

		@Override
		public boolean contains(final String className) {
			for (final Pattern pattern : patterns) {
				if (pattern.matcher(className).matches()) return true;
			}
			return false;
		}
	}

}