    001// Copyright 2006, 2007, 2008, 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 org.apache.tapestry5.services.Session;
    018
    019import java.lang.annotation.Documented;
    020import static java.lang.annotation.ElementType.FIELD;
    021import java.lang.annotation.Retention;
    022import static java.lang.annotation.RetentionPolicy.RUNTIME;
    023import java.lang.annotation.Target;
    024
    025import static org.apache.tapestry5.ioc.annotations.AnnotationUseContext.*;
    026import org.apache.tapestry5.ioc.annotations.UseWith;
    027
    028/**
    029 * Identifies a field as persistent, meaning its value persists from one request to the next. Different strategies exist
    030 * for how this is accomplished, the most common being the default, "session", which stores the field's value in the
    031 * {@link Session}.
    032 * <p/>
    033 * In most cases, the value will be omitted and will default to the empty string. This forces a search for the correct
    034 * strategy. Starting with the component (or mixin) itself, a check is made for the {@link Meta meta data property}
    035 * <code>tapestry.persistence-strategy</code>. If a value is found, it is used, otherwise the search continues up the
    036 * inheritance hierarchy, towards the page. If not found, then the "session" strategy is used.
    037 * <p/>
    038 * In this way, the session persistence strategy for a component and all of its sub-components can be controlled by the
    039 * containing component.
    040 *
    041 * @see org.apache.tapestry5.services.MetaDataLocator
    042 * @see org.apache.tapestry5.PersistenceConstants
    043 * @see ActivationRequestParameter
    044 */
    045@Target(FIELD)
    046@Documented
    047@Retention(RUNTIME)
    048@UseWith({COMPONENT,MIXIN,PAGE})
    049public @interface Persist
    050{
    051
    052    /**
    053     * The strategy used to persist the value. The default value, the empty string, allows persistence to be decided by
    054     * the containing component and component hierarchy.
    055     */
    056    String value() default "";
    057}