001    /*
002     * Copyright (C) 2007 The Guava Authors
003     *
004     * Licensed under the Apache License, Version 2.0 (the "License");
005     * you may not use this file except in compliance with the License.
006     * You may obtain a copy of the License at
007     *
008     * http://www.apache.org/licenses/LICENSE-2.0
009     *
010     * Unless required by applicable law or agreed to in writing, software
011     * distributed under the License is distributed on an "AS IS" BASIS,
012     * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
013     * See the License for the specific language governing permissions and
014     * limitations under the License.
015     */
016    
017    package com.google.common.eventbus;
018    
019    import com.google.common.annotations.Beta;
020    
021    import java.lang.annotation.ElementType;
022    import java.lang.annotation.Retention;
023    import java.lang.annotation.RetentionPolicy;
024    import java.lang.annotation.Target;
025    
026    /**
027     * Marks a method as an event handler, as used by
028     * {@link AnnotatedHandlerFinder} and {@link EventBus}.
029     *
030     * <p>The type of event will be indicated by the method's first (and only)
031     * parameter.  If this annotation is applied to methods with zero parameters,
032     * or more than one parameter, the object containing the method will not be able
033     * to register for event delivery from the {@link EventBus}.
034     *
035     * <p>Unless also annotated with @{@link AllowConcurrentEvents}, event handler
036     * methods will be invoked serially by each event bus that they are registered
037     * with.
038     *
039     * @author Cliff Biffle
040     * @since 10.0
041     */
042    @Retention(RetentionPolicy.RUNTIME)
043    @Target(ElementType.METHOD)
044    @Beta
045    public @interface Subscribe {
046    }