# Annotations.java

    /*
     * Copyright (c) 2008, 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.util;

    import java.lang.annotation.Annotation;
    import java.lang.reflect.AccessibleObject;
    import java.lang.reflect.AnnotatedElement;
    import java.lang.reflect.Type;
    import org.qi4j.functional.Function;
    import org.qi4j.functional.Iterables;
    import org.qi4j.functional.Specification;

    import static org.qi4j.api.util.Classes.interfacesOf;
    import static org.qi4j.api.util.Classes.typeOf;
    import static org.qi4j.functional.Iterables.flatten;
    import static org.qi4j.functional.Iterables.flattenIterables;
    import static org.qi4j.functional.Iterables.iterable;
    import static org.qi4j.functional.Iterables.map;

    /**
     * Useful methods for handling Annotations.
     */
    public final class Annotations
    {
        public static Function<Type, Iterable<Annotation>> ANNOTATIONS_OF = Classes.forTypes( new Function<Type, Iterable<Annotation>>()
        {
            @Override
            public Iterable<Annotation> map( Type type )
            {
                return Iterables.iterable( Classes.RAW_CLASS.map( type ).getAnnotations() );
            }
        } );

        public static Specification<AnnotatedElement> hasAnnotation( final Class<? extends Annotation> annotationType )
        {
            return new Specification<AnnotatedElement>()
            {
                @Override
                public boolean satisfiedBy( AnnotatedElement element )
                {
                    return element.getAnnotation( annotationType ) != null;
                }
            };
        }

        public static Function<Annotation, Class<? extends Annotation>> type()
        {
            return new Function<Annotation, Class<? extends Annotation>>()
            {
                @Override
                public Class<? extends Annotation> map( Annotation annotation )
                {
                    return annotation.annotationType();
                }
            };
        }

        public static Specification<Annotation> isType( final Class<? extends Annotation> annotationType )
        {
            return new Specification<Annotation>()
            {
                @Override
                public boolean satisfiedBy( Annotation annotation )
                {
                    return annotation.annotationType().equals( annotationType );
                }
            };
        }

        public static <T extends Annotation> T annotationOn( Type type, Class<T> annotationType )
        {
            return annotationType.cast( Classes.RAW_CLASS.map( type ).getAnnotation( annotationType ) );
        }

        public static Iterable<Annotation> findAccessorAndTypeAnnotationsIn( AccessibleObject accessor )
        {
            return flatten( iterable( accessor.getAnnotations() ),
                            flattenIterables( map( Annotations.ANNOTATIONS_OF, interfacesOf( typeOf( accessor ) ) ) ) );
        }
    }