1   // Copyright 2006, 2007, 2008 The Apache Software Foundation
    2   //
    3   // Licensed under the Apache License, Version 2.0 (the "License");
    4   // you may not use this file except in compliance with the License.
    5   // You may obtain a copy of the License at
    6   //
    7   //     http://www.apache.org/licenses/LICENSE-2.0
    8   //
    9   // Unless required by applicable law or agreed to in writing, software
   10   // distributed under the License is distributed on an "AS IS" BASIS,
   11   // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   12   // See the License for the specific language governing permissions and
   13   // limitations under the License.
   14   
   15   package org.apache.tapestry5.ioc.annotations;
   16   
   17   import java.lang.annotation.Documented;
   18   import static java.lang.annotation.ElementType.*;
   19   import java.lang.annotation.Retention;
   20   import static java.lang.annotation.RetentionPolicy.RUNTIME;
   21   import java.lang.annotation.Target;
   22   
   23   /**
   24    * This annotation serves is something of the Swiss Army knife for operations related to injection of dependencies into
   25    * an arbitrary method of Java Bean.
   26    * <p/>
   27    * <p>It marks parameters that should be injected in the IoC container, and it marks fields that should be injected
   28    * inside Tapestry components.
   29    * <p/>
   30    * In terms of the IoC container; normally, resources take precedence over annotations when injecting. The Inject
   31    * annotation overrides this default, forcing the resolution of the parameters value via the master {@link
   32    * org.apache.tapestry5.ioc.ObjectProvider}, even when the parameter's type matches a type that is normally a resource.
   33    * This is most often used in conjunction with {@link org.apache.tapestry5.ioc.annotations.Value} annotation when
   34    * injecting a string, as normally, the String would be matched as the service id.
   35    * <p/>
   36    * For service implementations, module classes, and other objects constructed via  {@link
   37    * org.apache.tapestry5.ioc.ObjectLocator#autobuild(Class)}, this annotation indicates that an injection is desired on
   38    * the field, as with fields of a Tapestry component.
   39    * <p/>
   40    * In terms of the IoC container, the Inject annotation is only used on parameters to service builder methods (and
   41    * contributor and decorator methods) and on module class constructors. constructors. However, inside Tapestry
   42    * components (<em>and only inside components</em>), it may be applied to fields. On fields that require injection, the
   43    * Inject annotation is <em>required</em>.
   44    * <p/>
   45    * Finally, on a constructor, this is used to indicate <em>which</em> constructor should be used when more than one is
   46    * available.
   47    *
   48    * @see org.apache.tapestry5.ioc.ObjectProvider
   49    */
   50   @Target(
   51           {PARAMETER, FIELD, CONSTRUCTOR})
   52   @Retention(RUNTIME)
   53   @Documented
   54   public @interface Inject
   55   {
   56   
   57   }