001// Licensed under the Apache License, Version 2.0 (the "License");
002// you may not use this file except in compliance with the License.
003// You may obtain a copy of the License at
004//
005//     http://www.apache.org/licenses/LICENSE-2.0
006//
007// Unless required by applicable law or agreed to in writing, software
008// distributed under the License is distributed on an "AS IS" BASIS,
009// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
010// See the License for the specific language governing permissions and
011// limitations under the License.
012
013package org.apache.tapestry5.ioc.annotations;
014
015import org.apache.tapestry5.ioc.def.ServiceDef;
016
017import java.lang.annotation.Documented;
018import java.lang.annotation.Retention;
019import java.lang.annotation.Target;
020
021import static java.lang.annotation.ElementType.METHOD;
022import static java.lang.annotation.ElementType.TYPE;
023import static java.lang.annotation.RetentionPolicy.RUNTIME;
024
025/**
026 * Used to define one or more {@linkplain ServiceDef#getMarkers() marker annotations} for a service implementation. This
027 * allows for injection based on the combination of type and marker interface. These marker interfaces should not have
028 * any values. The mere presence of the marker annotation is all that is needed.
029 *
030 * When applied to a module class, this sets the default markers for all services within the module.  Markers are
031 * additive, so a Marker annotation on the implementation class and/or specified with {@link
032 * org.apache.tapestry5.ioc.ServiceBindingOptions#withMarker(Class[])} will accumulate; a service may have any number of
033 * markers.  Generally one or two is enough.
034 *
035 * @see org.apache.tapestry5.ioc.ObjectLocator#getService(Class, Class[])
036 */
037@Target(
038        {TYPE, METHOD})
039@Retention(RUNTIME)
040@Documented
041@UseWith({AnnotationUseContext.SERVICE, AnnotationUseContext.MODULE})
042public @interface Marker
043{
044    /**
045     * The type of annotation (which will be present at the injection point).
046     */
047    Class[] value();
048}