    001// Licensed under the Apache License, Version 2.0 (the "License");
    002// you may not use this file except in compliance with the License.
    003// You may obtain a copy of the License at
    004//
    005//     http://www.apache.org/licenses/LICENSE-2.0
    006//
    007// Unless required by applicable law or agreed to in writing, software
    008// distributed under the License is distributed on an "AS IS" BASIS,
    009// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    010// See the License for the specific language governing permissions and
    011// limitations under the License.
    012
    013package org.apache.tapestry5.annotations;
    014
    015import org.apache.tapestry5.http.services.Session;
    016import org.apache.tapestry5.ioc.annotations.UseWith;
    017
    018import java.lang.annotation.Documented;
    019import java.lang.annotation.Retention;
    020import java.lang.annotation.Target;
    021
    022import static java.lang.annotation.ElementType.FIELD;
    023import static java.lang.annotation.RetentionPolicy.RUNTIME;
    024import static org.apache.tapestry5.ioc.annotations.AnnotationUseContext.*;
    025
    026/**
    027 * Identifies a field as persistent, meaning its value persists from one request to the next. Different strategies exist
    028 * for how this is accomplished, the most common being the default, "session", which stores the field's value in the
    029 * {@link Session}.
    030 *
    031 * In most cases, the value will be omitted and will default to the empty string. This forces a search for the correct
    032 * strategy. Starting with the component (or mixin) itself, a check is made for the {@link Meta meta data property}
    033 * <code>tapestry.persistence-strategy</code>. If a value is found, it is used, otherwise the search continues up the
    034 * inheritance hierarchy, towards the page. If not found, then the "session" strategy is used.
    035 *
    036 * In this way, the session persistence strategy for a component and all of its sub-components can be controlled by the
    037 * containing component.
    038 *
    039 * @see org.apache.tapestry5.services.MetaDataLocator
    040 * @see org.apache.tapestry5.PersistenceConstants
    041 * @see ActivationRequestParameter
    042 */
    043@Target(FIELD)
    044@Documented
    045@Retention(RUNTIME)
    046@UseWith({COMPONENT,MIXIN,PAGE})
    047public @interface Persist
    048{
    049
    050    /**
    051     * The strategy used to persist the value. The default value, the empty string, allows persistence to be decided by
    052     * the containing component and component hierarchy.
    053     */
    054    String value() default "";
    055}