001    // Copyright 2010 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.annotations;
016    
017    import static java.lang.annotation.RetentionPolicy.RUNTIME;
018    import static org.apache.tapestry5.ioc.annotations.AnnotationUseContext.COMPONENT;
019    import static org.apache.tapestry5.ioc.annotations.AnnotationUseContext.MIXIN;
020    import static org.apache.tapestry5.ioc.annotations.AnnotationUseContext.PAGE;
021    
022    import java.lang.annotation.Documented;
023    import java.lang.annotation.ElementType;
024    import java.lang.annotation.Retention;
025    import java.lang.annotation.Target;
026    
027    import org.apache.tapestry5.internal.transform.HeartbeatDeferredWorker;
028    import org.apache.tapestry5.ioc.annotations.UseWith;
029    import org.apache.tapestry5.services.Heartbeat;
030    
031    /**
032     * Marks a component method as deferred until the end of the {@link Heartbeat}. This
033     * is only allowed on void methods that do not throw exceptions. The invocation is captured
034     * and will execute at the end of the current Heartbeat.
035     * <p>
036     * This annotation should be used with care, since deferring the invocation can change its semantics. For example, the
037     * value stored in instance variables may change between the time the method is invoked and the time it eventually
038     * executes. Likewise, runtime exceptions thrown by the method can not be caught by the invoking method.
039     * <p>
040     * Annotated methods must return void, and not declare any checked exceptions.
041     * 
042     * @since 5.2.0
043     * @see HeartbeatDeferredWorker
044     */
045    @Target(ElementType.METHOD)
046    @Retention(RUNTIME)
047    @Documented
048    @UseWith(
049    { COMPONENT, MIXIN, PAGE })
050    public @interface HeartbeatDeferred
051    {
052    
053    }