001    // Copyright 2007, 2009, 2011 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 org.apache.tapestry5.ioc.def.ServiceDef;
018    
019    import java.lang.annotation.Documented;
020    import java.lang.annotation.Retention;
021    import java.lang.annotation.Target;
022    
023    import static java.lang.annotation.ElementType.METHOD;
024    import static java.lang.annotation.ElementType.TYPE;
025    import static java.lang.annotation.RetentionPolicy.RUNTIME;
026    
027    /**
028     * Used to define one or more {@linkplain ServiceDef#getMarkers() marker annotations} for a service implementation. This
029     * allows for injection based on the combination of type and marker interface. These marker interfaces should not have
030     * any values. The mere presence of the marker annotation is all that is needed.
031     * <p/>
032     * When applied to a module class, this sets the default markers for all services within the module.  Markers are
033     * additive, so a Marker annotation on the implementation class and/or specified with {@link
034     * org.apache.tapestry5.ioc.ServiceBindingOptions#withMarker(Class[])} will accumulate; a service may have any number of
035     * markers.  Generally one or two is enough.
036     *
037     * @see org.apache.tapestry5.ioc.ObjectLocator#getService(Class, Class[])
038     */
039    @Target(
040            {TYPE, METHOD})
041    @Retention(RUNTIME)
042    @Documented
043    @UseWith({AnnotationUseContext.SERVICE, AnnotationUseContext.MODULE})
044    public @interface Marker
045    {
046        /**
047         * The type of annotation (which will be present at the injection point).
048         */
049        Class[] value();
050    }