001    // Copyright 2006, 2007, 2008 The Apache Software Foundation
002    //
003    // Licensed under the Apache License, Version 2.0 (the "License");
004    // you may not use this file except in compliance with the License.
005    // You may obtain a copy of the License at
006    //
007    //     http://www.apache.org/licenses/LICENSE-2.0
008    //
009    // Unless required by applicable law or agreed to in writing, software
010    // distributed under the License is distributed on an "AS IS" BASIS,
011    // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
012    // See the License for the specific language governing permissions and
013    // limitations under the License.
014    
015    package org.apache.tapestry5.ioc.annotations;
016    
017    import java.lang.annotation.Documented;
018    import static java.lang.annotation.ElementType.*;
019    import java.lang.annotation.Retention;
020    import static java.lang.annotation.RetentionPolicy.RUNTIME;
021    import java.lang.annotation.Target;
022    
023    /**
024     * This annotation serves is something of the Swiss Army knife for operations related to injection of dependencies into
025     * an arbitrary method of Java Bean.
026     * <p/>
027     * <p>It marks parameters that should be injected in the IoC container, and it marks fields that should be injected
028     * inside Tapestry components.
029     * <p/>
030     * In terms of the IoC container; normally, resources take precedence over annotations when injecting. The Inject
031     * annotation overrides this default, forcing the resolution of the parameters value via the master {@link
032     * org.apache.tapestry5.ioc.ObjectProvider}, even when the parameter's type matches a type that is normally a resource.
033     * This is most often used in conjunction with {@link org.apache.tapestry5.ioc.annotations.Value} annotation when
034     * injecting a string, as normally, the String would be matched as the service id.
035     * <p/>
036     * For service implementations, module classes, and other objects constructed via  {@link
037     * org.apache.tapestry5.ioc.ObjectLocator#autobuild(Class)}, this annotation indicates that an injection is desired on
038     * the field, as with fields of a Tapestry component.
039     * <p/>
040     * In terms of the IoC container, the Inject annotation is only used on parameters to service builder methods (and
041     * contributor and decorator methods) and on module class constructors. constructors. However, inside Tapestry
042     * components (<em>and only inside components</em>), it may be applied to fields. On fields that require injection, the
043     * Inject annotation is <em>required</em>.
044     * <p/>
045     * Finally, on a constructor, this is used to indicate <em>which</em> constructor should be used when more than one is
046     * available.
047     *
048     * @see org.apache.tapestry5.ioc.ObjectProvider
049     */
050    @Target(
051            {PARAMETER, FIELD, CONSTRUCTOR})
052    @Retention(RUNTIME)
053    @Documented
054    public @interface Inject
055    {
056    
057    }