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package com.abdennebi.version;

import java.io.IOException;
import java.io.InputStream;
import java.net.MalformedURLException;
import java.net.URL;
import java.util.jar.Attributes;
import java.util.jar.Manifest;

public class VersionUtil {

	public static void main(String[] args) {

		System.out.println(readVersion());
	}

	public static String readVersion() {

		URL pathToManifest = null;

		try {
			pathToManifest = new URL(getPathToManifest());

			InputStream inputStream = pathToManifest.openStream();

			Manifest manifest = new Manifest(inputStream);

			String version = manifest.getMainAttributes().getValue(Attributes.Name.IMPLEMENTATION_VERSION);

			inputStream.close();

			return version;

		} catch (MalformedURLException e) {
			throw new UnreadableVersionException(e);
		} catch (IOException e) {
			throw new UnreadableVersionException(e);
		}
	}

	private static String getPathToManifest(){

		// 1 - Lire le nom de la classe
		String classSimpleName = VersionUtil.class.getSimpleName() + ".class";
		// classSimpleName = VersionUtil.class

		// 2 - Récupérer le chemin physique de la classe
		String pathToClass = VersionUtil.class.getResource(classSimpleName).toString();

		// pathToClass = file:/C:/workspace/VersionUtil/bin/com/abdennebi/version/VersionUtil.class
		// pathToClass = jar:file:/C:/version.jar!/com/abdennebi/version/VersionUtil.class

		// 3 - Récupérer le chemin de la classe à partir de la racine du classpath
		String classFullName = VersionUtil.class.getName().replace('.', '/') + ".class";
		// classFullName = com/abdennebi/version/VersionUtil.class

		// 4 - Récupérer le chemin complet vers MANIFEST.MF
		String pathToManifest = pathToClass.substring( 0, pathToClass.length() - (classFullName.length())) + "META-INF/MANIFEST.MF";
		// pathToManifest = file:/C:/workspace/VersionUtil/bin/META-INF/MANIFEST.MF
		// pathToManifest = jar:file:/C:/version.jar!/META-INF/MANIFEST.MF

		return pathToManifest;
	}

	public static class UnreadableVersionException extends RuntimeException {

		public UnreadableVersionException(Throwable cause) {
			super(cause);
		}

		private static final long serialVersionUID = 1L;
	}
}