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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, 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.util;

import java.io.BufferedReader;
import java.io.File;
import java.io.FileWriter;
import java.io.IOException;
import java.io.InputStreamReader;
import java.net.URL;
import java.util.Enumeration;
import java.util.HashMap;
import java.util.Map;
import java.util.Map.Entry;

import javax.xml.ws.Service;

/**
 * Combines {@link Service} information from all JAR files on the classpath.
 * 
 * @author Johannes Schindelin
 * @author Mark Hiner
 */
public class ServiceCombiner implements Combiner {

	private static final String SERVICES_PREFIX = "META-INF/services/";

	@Override
	public void combine(final File outputDirectory) throws IOException {

		final Map files =
			new HashMap<>();
		final Enumeration directories =
			Thread.currentThread().getContextClassLoader().getResources(
				SERVICES_PREFIX);

		// Iterate over all the service files
		while (directories.hasMoreElements()) {
			for (final URL url : FileUtils.listContents(directories.nextElement())) {
				final String urlString = url.toString();
				if (urlString.endsWith("/")) {
					continue;
				}
				final String fileName =
					urlString.substring(urlString.lastIndexOf('/') + 1);
				StringBuilder builder = files.get(fileName);
				if (builder == null) {
					builder = new StringBuilder();
					// Create a base entry for a service type
					files.put(fileName, builder);
				}
				final InputStreamReader reader =
					new InputStreamReader(url.openStream());
				final BufferedReader buffered = new BufferedReader(reader);
				for (;;) {
					final String line = buffered.readLine();
					if (line == null) {
						break;
					}
					builder.append(line).append('\n');
				}
				buffered.close();
			}
		}

		if (files.isEmpty()) {
			return;
		}

		// Write the unified serice files
		final File servicesDirectory = new File(outputDirectory, SERVICES_PREFIX);
		servicesDirectory.mkdirs();
		for (final Entry entry : files.entrySet()) {
			final FileWriter writer =
				new FileWriter(new File(servicesDirectory, entry.getKey()));
			writer.write(entry.getValue().toString());
			writer.close();
		}
	}

	// -- Main method --

	public static void main(final String... args) throws IOException {
		new ServiceCombiner().combine(args.length > 0 ? new File(args[0]) : null);
	}
}