Java tutorial
/* * Copyright (C) 2008, Shawn O. Pearce <spearce@spearce.org> * and other copyright owners as documented in the project's IP log. * * This program and the accompanying materials are made available * under the terms of the Eclipse Distribution License v1.0 which * accompanies this distribution, is reproduced below, and is * available at http://www.eclipse.org/org/documents/edl-v10.php * * All rights reserved. * * Redistribution and use in source and binary forms, with or * without modification, are permitted provided that the following * conditions are met: * * - Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * * - 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. * * - Neither the name of the Eclipse Foundation, Inc. nor the * names of its contributors may be used to endorse or promote * products derived from this software without specific prior * written permission. * * 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 OWNER 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. */ package org.eclipse.jgit.pgm; import static java.nio.charset.StandardCharsets.UTF_8; import java.io.BufferedReader; import java.io.IOException; import java.io.InputStreamReader; import java.net.URL; import java.util.ArrayList; import java.util.Arrays; import java.util.Collection; import java.util.Enumeration; import java.util.HashMap; import java.util.Map; import java.util.Vector; /** * List of all commands known by jgit's command line tools. * <p> * Commands are implementations of {@link org.eclipse.jgit.pgm.TextBuiltin}, * with an optional {@link org.eclipse.jgit.pgm.Command} class annotation to * insert additional documentation or override the default command name (which * is guessed from the class name). * <p> * Commands may be registered by adding them to a services file in the same JAR * (or classes directory) as the command implementation. The service file name * is <code>META-INF/services/org.eclipse.jgit.pgm.TextBuiltin</code> and it * contains one concrete implementation class name per line. * <p> * Command registration is identical to Java 6's services, however the catalog * uses a lightweight wrapper to delay creating a command instance as much as * possible. This avoids initializing the AWT or SWT GUI toolkits even if the * command's constructor might require them. */ public class CommandCatalog { private static final CommandCatalog INSTANCE = new CommandCatalog(); /** * Locate a single command by its user friendly name. * * @param name * name of the command. Typically in dash-lower-case-form, which * was derived from the DashLowerCaseForm class name. * @return the command instance; null if no command exists by that name. */ public static CommandRef get(String name) { return INSTANCE.commands.get(name); } /** * Get all commands sorted by their name * * @return all known commands, sorted by command name. */ public static CommandRef[] all() { return toSortedArray(INSTANCE.commands.values()); } /** * Get all common commands sorted by their name * * @return all common commands, sorted by command name. */ public static CommandRef[] common() { final ArrayList<CommandRef> common = new ArrayList<>(); for (CommandRef c : INSTANCE.commands.values()) if (c.isCommon()) common.add(c); return toSortedArray(common); } private static CommandRef[] toSortedArray(Collection<CommandRef> c) { final CommandRef[] r = c.toArray(new CommandRef[0]); Arrays.sort(r, (CommandRef o1, CommandRef o2) -> o1.getName().compareTo(o2.getName())); return r; } private final ClassLoader ldr; private final Map<String, CommandRef> commands; private CommandCatalog() { ldr = Thread.currentThread().getContextClassLoader(); commands = new HashMap<>(); final Enumeration<URL> catalogs = catalogs(); while (catalogs.hasMoreElements()) scan(catalogs.nextElement()); } private Enumeration<URL> catalogs() { try { final String pfx = "META-INF/services/"; //$NON-NLS-1$ return ldr.getResources(pfx + TextBuiltin.class.getName()); } catch (IOException err) { return new Vector<URL>().elements(); } } private void scan(URL cUrl) { try (BufferedReader cIn = new BufferedReader(new InputStreamReader(cUrl.openStream(), UTF_8))) { String line; while ((line = cIn.readLine()) != null) { if (line.length() > 0 && !line.startsWith("#")) //$NON-NLS-1$ load(line); } } catch (IOException e) { // Ignore errors } } private void load(String cn) { final Class<? extends TextBuiltin> clazz; try { clazz = Class.forName(cn, false, ldr).asSubclass(TextBuiltin.class); } catch (ClassNotFoundException | ClassCastException notBuiltin) { // Doesn't exist, even though the service entry is present. // Isn't really a builtin, even though its listed as such. return; } final CommandRef cr; final Command a = clazz.getAnnotation(Command.class); if (a != null) cr = new CommandRef(clazz, a); else cr = new CommandRef(clazz); commands.put(cr.getName(), cr); } }