001    /*
002     * ============================================================================
003     * GNU Lesser General Public License
004     * ============================================================================
005     *
006     * Beanlet - JSE Application Container.
007     * Copyright (C) 2006  Leon van Zantvoort
008     * 
009     * This library is free software; you can redistribute it and/or
010     * modify it under the terms of the GNU Lesser General Public
011     * License as published by the Free Software Foundation; either
012     * version 2.1 of the License, or (at your option) any later version.
013     * 
014     * This library is distributed in the hope that it will be useful,
015     * but WITHOUT ANY WARRANTY; without even the implied warranty of
016     * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
017     * Lesser General Public License for more details.
018     * 
019     * You should have received a copy of the GNU Lesser General Public
020     * License along with this library; if not, write to the Free Software
021     * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307, USA.
022     * 
023     * Leon van Zantvoort
024     * 243 Acalanes Drive #11
025     * Sunnyvale, CA 94086
026     * USA
027     *
028     * zantvoort@users.sourceforge.net
029     * http://beanlet.org
030     */
031    package org.beanlet;
032    
033    /**
034     * <p>
035     * Provides instances of <code>T</code>. Typically implemented by an injector. For
036     * any type <code>T</code> that can be injected, you can also inject
037     * <code>Provider&lt;T&gt;</code>. Compared to injecting <code>T</code> directly, injecting
038     * <code>Provider&lt;T&gt;</code> enables:
039     *
040     *  <ul>
041     *  <li>retrieving multiple instances.</li>
042     *  <li>lazy or optional retrieval of an instance.</li>
043     *  <li>breaking circular dependencies.</li>
044     *  <li>abstracting scope so you can look up an instance in a smaller scope
045     *     from an instance in a containing scope.</li>
046     * </ul>
047     *
048     * <p>For example:
049     *
050     * <pre>
051     *  class Car {
052     *    &#064;Inject Car(Provider&lt;Seat> seatProvider) {
053     *      Seat driver = seatProvider.get();
054     *      Seat passenger = seatProvider.get();
055     *      ...
056     *    }
057     *  }</pre>
058     * <P>
059     *
060     * @author Leon van Zantvoort
061     */
062    public interface Provider<T> {
063    
064    
065        /**
066         * Provides a fully-constructed and injected instance of {@code T}
067         */
068        T get();
069    }