SingletonDefault.java

/*
 * Copyright 2012, We The Internet Ltd.
 *
 * All rights reserved.
 *
 * Distributed under a modified BSD License as follow:
 *
 * 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, unless otherwise
 * agreed to in a written document signed by a director of We The Internet Ltd.
 *
 * Neither the name of We The Internet 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 HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
 * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
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package xapi.annotation.inject;

import java.lang.annotation.Documented;
import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;


/**
 * Used to link a singleton implementation class to an injectable interface.
 *
 * <br/><br/>
 *
 * There should only ever be one @DefaulImpl per service interface;
 * unless you are writing a new service, you should not use this annotation
 * and instead prefer {@link SingletonOverride} to inject over top the default.
 *
 * <br/><br/>
 *
 * Example:
 *
 * <br/>
 *
 * static interface MyService{}
 *
 * <br/>
 *
 * <pre>@SingletonDefault(implFor=MyService.class)</pre>
 * static class MyServiceImpl implements MyService{}
 *
 * <br/><br/>
 *
 * //returns a singleton instance of MyServiceImpl
 * <br/>
 * MyService service = X_Inject.singleton(MyService.class);

 * <br/><br/>
 *
 * @author James X. Nelson (james@wetheinter.net, @james)
 */
@Documented
@Target(value=ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
public @interface SingletonDefault {

  /**
   * @return - The class object for the instance / class the annotated type is implementing.
   *
   * The return value of this method determines which class can be used to request the
   * singleton from X_Inject.
   */
  Class<?> implFor();

}