| /* |
| * Copyright (C) 2009 The JSR-330 Expert Group |
| * |
| * Licensed under the Apache License, Version 2.0 (the "License"); |
| * you may not use this file except in compliance with the License. |
| * You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, software |
| * distributed under the License is distributed on an "AS IS" BASIS, |
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| * See the License for the specific language governing permissions and |
| * limitations under the License. |
| */ |
| |
| package javax.inject; |
| |
| import java.lang.annotation.Target; |
| import java.lang.annotation.Retention; |
| import java.lang.annotation.Documented; |
| import static java.lang.annotation.RetentionPolicy.RUNTIME; |
| import static java.lang.annotation.ElementType.ANNOTATION_TYPE; |
| |
| /** |
| * 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) |
| * @javax.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 javax.inject.Singleton @Singleton |
| */ |
| @Target(ANNOTATION_TYPE) |
| @Retention(RUNTIME) |
| @Documented |
| public @interface Scope {} |