001// Copyright 2006, 2009, 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 015package org.apache.tapestry5.annotations; 016 017import java.lang.annotation.Documented; 018import static java.lang.annotation.ElementType.FIELD; 019import java.lang.annotation.Retention; 020import static java.lang.annotation.RetentionPolicy.RUNTIME; 021import java.lang.annotation.Target; 022 023import static org.apache.tapestry5.ioc.annotations.AnnotationUseContext.*; 024import org.apache.tapestry5.ioc.annotations.UseWith; 025 026/** 027 * Marker annotation placed on fields whose value should be retained past the end of the request. This is most often 028 * associated with fields that are <em>lazily loaded</em>. By marking such fields with the Retain annotation, the fields 029 * will <em>not</em> be discarded at the end of the request. 030 * <p/> 031 * This is quite different from {@link Persist}, because the value that's allowed to be retained is not stored 032 * persistently; it is simply not cleared out. A subsequent request, even from the same user, may be processed by a 033 * different instance of the page where the value is still null. 034 * <p/> 035 * This annotation should only be used with lazily-evaluated objects that contain no client-specific information. 036 * 037 * @deprecated This rarely used annotation is likely to cause threading issues starting in Tapestry 5.2 (which no longer 038 * pools pages 039 * but uses shared instances with externalized mutable state) 040 */ 041@Target(FIELD) 042@Retention(RUNTIME) 043@Documented 044@UseWith( 045{ COMPONENT, MIXIN, PAGE }) 046public @interface Retain 047{ 048 049}