| // Copyright 2008-2014 The Apache Software Foundation |
| // |
| // 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.annotations; |
| |
| import java.lang.annotation.*; |
| |
| import static org.apache.tapestry5.ioc.annotations.AnnotationUseContext.*; |
| import org.apache.tapestry5.ioc.annotations.UseWith; |
| |
| /** |
| * Indicates that a method should only be evaluated once per request and the result cached. |
| * Further calls to the method during the same request will return the cached result. |
| * However, if the method's component occurs more than once within an enclosing component, |
| * the cached results will be distinct for each occurrence. |
| * <p/> |
| * This annotation is commonly used on getters for component properties: |
| * <pre> |
| * @Cached |
| * Date getNow() { |
| * new Date(); |
| * } |
| * </pre> |
| * You may not apply @Cached to void methods or methods with parameters. |
| * <p/> |
| * Note that this annotation is inheritance-safe; if a subclass calls a superclass method that |
| * has @Cached then the value the subclass method gets is the cached value. |
| * <p/> |
| * The watch parameter can be passed a binding expression which will be evaluated each time the method is called. The |
| * method will then only be executed the first time it is called and after that only when the value of the binding |
| * changes. This can be used, for instance, to have the method only evaluated once per iteration of a loop by setting |
| * watch to the value or index of the loop. |
| */ |
| @Target(ElementType.METHOD) |
| @Retention(RetentionPolicy.RUNTIME) |
| @Documented |
| @UseWith({COMPONENT,MIXIN,PAGE}) |
| public @interface Cached |
| { |
| /** |
| * The optional binding to watch (default binding prefix is "prop"). |
| */ |
| String watch() default ""; |
| } |