001    // Copyright 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    
015    package org.apache.tapestry5.ioc.annotations;
016    
017    import java.lang.annotation.Documented;
018    import java.lang.annotation.Retention;
019    import java.lang.annotation.Target;
020    
021    import static java.lang.annotation.ElementType.METHOD;
022    import static java.lang.annotation.RetentionPolicy.RUNTIME;
023    
024    /**
025     * Marks a service contribution method within a module as being optional: it is not an error if the contribution does not match against an actual service. In that case, the
026     * method will simply never be invoked.
027     *
028     * @see Contribute
029     * @since 5.3
030     */
031    @Target(METHOD)
032    @Retention(RUNTIME)
033    @Documented
034    @UseWith(AnnotationUseContext.MODULE)
035    public @interface Optional
036    {
037    }