    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
    015    package org.apache.tapestry5.annotations;
    016
    017    import org.apache.tapestry5.services.Session;
    018
    019    import java.lang.annotation.Documented;
    020    import static java.lang.annotation.ElementType.FIELD;
    021    import java.lang.annotation.Retention;
    022    import static java.lang.annotation.RetentionPolicy.RUNTIME;
    023    import java.lang.annotation.Target;
    024
    025    import static org.apache.tapestry5.ioc.annotations.AnnotationUseContext.*;
    026    import 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})
    049    public @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    }