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
015package org.apache.tapestry5.ioc.annotations;
016
017import org.apache.tapestry5.ioc.def.ServiceDef;
018
019import java.lang.annotation.Documented;
020import java.lang.annotation.Retention;
021import java.lang.annotation.Target;
022
023import static java.lang.annotation.ElementType.METHOD;
024import static java.lang.annotation.ElementType.TYPE;
025import 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})
044public @interface Marker
045{
046    /**
047     * The type of annotation (which will be present at the injection point).
048     */
049    Class[] value();
050}