content: package act.app.conf;
  
  /*-
   * #%L
   * ACT Framework
   * %%
   * Copyright (C) 2014 - 2017 ActFramework
   * %%
   * 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.
   * #L%
   */
  
  import act.app.event.SysEventId;
  
  import java.lang.annotation.*;
  
  /**
   * This annotation marks a class as auto configured class. E.g
   *
   * ```java
   * {@literal @}AutoConfig("foo") class Foo {
   *     public static final Const<String> name = $.constant("foo1");
   *     public static class Bar {
   *         public static final Const<Integer> limit = $.constant(100);
   *     }
   *     ...
   *     public void x() {
   *         System.out.println(Foo.name.get());
   *         System.out.println(Foo.Bar.limit.get());
   *     }
   * }
   * ```
   *
   * As the above classs `Foo` has been annotated with `AutoConfig("foo")`,
   * ActFramework will automatically configure the class by setting the
   * static field `name` and `Bar.limit` if the following configurations
   * exists:
   *
   * 1. foo.name=foo2
   * 2. foo.bar.limit=500
   *
   * With the above configuration, when calling new Foo().x(), it will print
   * out:
   *
   * ```
   * foo2
   * 500
   * ```
   *
   * instead of
   *
   * ```
   * foo1
   * 100
   * ```
   *
   * *Note* the static fields are populated on {@link SysEventId#START event},
   * meaning any logic in your application executed before app start shall NOT refer to
   * auto config class's configurable fields
   */
  @Documented
  @Inherited
  @Retention(RetentionPolicy.RUNTIME)
  @Target(java.lang.annotation.ElementType.TYPE)
  public @interface AutoConfig {
      /**
       * define namespace of the configuration
       */
      String value() default "app";
  }
  