# Tagged.java

    /*
     * Copyright (c) 2009, Rickard Öberg. All Rights Reserved.
     *
     * Licensed under the Apache License, Version 2.0 (the "License");
     * you may not use this file except in compliance with the License.
     * You may obtain a copy of the License at http://www.apache.org/licenses/LICENSE-2.0
     * Unless required by applicable law or agreed to in writing, software
     * distributed under the License is distributed on an "AS IS" BASIS,
     * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     * See the License for the specific language governing permissions and
     * limitations under the License.
     *
     */

    package org.qi4j.api.service.qualifier;

    import java.lang.annotation.Retention;
    import java.lang.annotation.RetentionPolicy;
    import org.qi4j.api.service.ServiceReference;
    import org.qi4j.functional.Specification;

    /**
     * Filter services based on tags. Tags can be set using the ServiceTags meta-info, like so:
     * <pre><code>
     * module.addService(MyService.class).taggedWith(new ServiceTags("onetag","twotag"));
     * </code></pre>
     *
     * and then at an injection point you can do this:
     *
     * <pre><code>
     * &#64;Service &#64;Tagged("onetag") MyService service;
     * </code></pre>
     * to get only a service tagged with MyService. If several match only the first match is used.
     */
    @Retention( RetentionPolicy.RUNTIME )
    @Qualifier( Tagged.TaggedQualifier.class )
    public @interface Tagged
    {
        public abstract String[] value();

        /**
         * Tagged Annotation Qualifier.
         * See {@link Tagged}.
         */
        public final class TaggedQualifier
            implements AnnotationQualifier<Tagged>
        {
            @Override
            public Specification<ServiceReference<?>> qualifier( Tagged tagged )
            {
                return ServiceQualifier.withTags( tagged.value() );
            }
        }
    }