GitCommand.java

/*
 * Copyright (C) 2010, Christian Halstrick <christian.halstrick@sap.com> 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
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package org.eclipse.jgit.api;

import java.text.MessageFormat;
import java.util.concurrent.Callable;
import java.util.concurrent.atomic.AtomicBoolean;

import org.eclipse.jgit.api.errors.GitAPIException;
import org.eclipse.jgit.internal.JGitText;
import org.eclipse.jgit.lib.Repository;

/**
 * Common superclass of all commands in the package {@code org.eclipse.jgit.api}
 * <p>
 * This class ensures that all commands fulfill the
 * {@link java.util.concurrent.Callable} interface. It also has a property
 * {@link #repo} holding a reference to the git
 * {@link org.eclipse.jgit.lib.Repository} this command should work with.
 * <p>
 * Finally this class stores a state telling whether it is allowed to call
 * {@link #call()} on this instance. Instances of
 * {@link org.eclipse.jgit.api.GitCommand} can only be used for one single
 * successful call to {@link #call()}. Afterwards this instance may not be used
 * anymore to set/modify any properties or to call {@link #call()} again. This
 * is achieved by setting the {@link #callable} property to false after the
 * successful execution of {@link #call()} and to check the state (by calling
 * {@link #checkCallable()}) before setting of properties and inside
 * {@link #call()}.
 *
 * @param <T>
 *            the return type which is expected from {@link #call()}
 */
public abstract class GitCommand<T> implements Callable<T> {
    /** The repository this command is working with */
    final protected Repository repo;

    /**
     * a state which tells whether it is allowed to call {@link #call()} on this
     * instance.
     */
    private AtomicBoolean callable = new AtomicBoolean(true);

    /**
     * Creates a new command which interacts with a single repository
     *
     * @param repo
     *            the {@link org.eclipse.jgit.lib.Repository} this command
     *            should interact with
     */
    protected GitCommand(Repository repo) {
        this.repo = repo;
    }

    /**
     * Get repository this command is working on
     *
     * @return the {@link org.eclipse.jgit.lib.Repository} this command is
     *         interacting with
     */
    public Repository getRepository() {
        return repo;
    }

    /**
     * Set's the state which tells whether it is allowed to call {@link #call()}
     * on this instance. {@link #checkCallable()} will throw an exception when
     * called and this property is set to {@code false}
     *
     * @param callable
     *            if <code>true</code> it is allowed to call {@link #call()} on
     *            this instance.
     */
    protected void setCallable(boolean callable) {
        this.callable.set(callable);
    }

    /**
     * Checks that the property {@link #callable} is {@code true}. If not then
     * an {@link java.lang.IllegalStateException} is thrown
     *
     * @throws java.lang.IllegalStateException
     *             when this method is called and the property {@link #callable}
     *             is {@code false}
     */
    protected void checkCallable() {
        if (!callable.get())
            throw new IllegalStateException(MessageFormat.format(
                    JGitText.get().commandWasCalledInTheWrongState
                    , this.getClass().getName()));
    }

    /**
     * {@inheritDoc}
     * <p>
     * Execute the command
     */
    @Override
    public abstract T call() throws GitAPIException;
}