// 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.apache.tapestry5.ioc.annotations;

import java.lang.annotation.Documented;
import java.lang.annotation.Retention;
import java.lang.annotation.Target;

import static java.lang.annotation.ElementType.METHOD;
import static java.lang.annotation.ElementType.TYPE;
import static java.lang.annotation.RetentionPolicy.RUNTIME;

/**
 * Used to define one or more 
 * <a href="https://tapestry.apache.org/current/apidocs/org/apache/tapestry5/ioc/def/ServiceDef.html">ServiceDef#getMarkers() marker annotations</a> for a service implementation. This
 * allows for injection based on the combination of type and marker interface. These marker interfaces should not have
 * any values. The mere presence of the marker annotation is all that is needed.
 *
 * When applied to a module class, this sets the default markers for all services within the module.  Markers are
 * additive, so a Marker annotation on the implementation class and/or specified with {@link
 * org.apache.tapestry5.ioc.ServiceBindingOptions#withMarker(Class[])} will accumulate; a service may have any number of
 * markers.  Generally one or two is enough.
 *
 * @see org.apache.tapestry5.commons.ObjectLocator#getService(Class, Class[])
 */
@Target(
        {TYPE, METHOD})
@Retention(RUNTIME)
@Documented
@UseWith({AnnotationUseContext.SERVICE, AnnotationUseContext.MODULE})
public @interface Marker
{
    /**
     * The type of annotation (which will be present at the injection point).
     */
    Class[] value();
}
