/*
* The MIT License (MIT)
*
* Copyright (c) 2016. Diorite (by Bartłomiej Mazur (aka GotoFinal))
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in all
* copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
* SOFTWARE.
*/
package org.diorite.inject;
import static java.lang.annotation.ElementType.ANNOTATION_TYPE;
import static java.lang.annotation.RetentionPolicy.RUNTIME;
import java.lang.annotation.Documented;
import java.lang.annotation.Retention;
import java.lang.annotation.Target;
/**
* Identifies scope annotations. A scope annotation applies to a class
* containing an injectable constructor and governs how the injector reuses
* instances of the type. By default, if no scope annotation is present, the
* injector creates an instance (by injecting the type's constructor), uses
* the instance for one injection, and then forgets it. If a scope annotation
* is present, the injector may retain the instance for possible reuse in a
* later injection. If multiple threads can access a scoped instance, its
* implementation should be thread safe. The implementation of the scope
* itself is left up to the injector.
*
* <p>In the following example, the scope annotation {@code @Singleton} ensures
* that we only have one Log instance:
*
* <pre>
* @Singleton
* class Log {
* void log(String message) { ... }
* }</pre>
*
* <p>The injector generates an error if it encounters more than one scope
* annotation on the same class or a scope annotation it doesn't support.
*
* <p>A scope annotation:
* <ul>
* <li>is annotated with {@code @Scope}, {@code @Retention(RUNTIME)},
* and typically {@code @Documented}.</li>
* <li>should not have attributes.</li>
* <li>is typically not {@code @Inherited}, so scoping is orthogonal to
* implementation inheritance.</li>
* <li>may have restricted usage if annotated with {@code @Target}. While
* this specification covers applying scopes to classes only, some
* injector configurations might use scope annotations
* in other places (on factory method results for example).</li>
* </ul>
*
* <p>For example:
*
* <pre>
* @java.lang.annotation.Documented
* @java.lang.annotation.Retention(RUNTIME)
* @org.diorite.inject.Scope
* public @interface RequestScoped {}</pre>
*
* <p>Annotating scope annotations with {@code @Scope} helps the injector
* detect the case where a programmer used the scope annotation on a class but
* forgot to configure the scope in the injector. A conservative injector
* would generate an error rather than not apply a scope.
*
* @see Singleton @Singleton
*/
@Target(ANNOTATION_TYPE)
@Retention(RUNTIME)
@Documented
public @interface Scope {}