    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
    015    package org.apache.tapestry5.annotations;
    016
    017    import static java.lang.annotation.ElementType.FIELD;
    018    import static java.lang.annotation.RetentionPolicy.RUNTIME;
    019    import static org.apache.tapestry5.ioc.annotations.AnnotationUseContext.COMPONENT;
    020    import static org.apache.tapestry5.ioc.annotations.AnnotationUseContext.MIXIN;
    021    import static org.apache.tapestry5.ioc.annotations.AnnotationUseContext.PAGE;
    022
    023    import java.lang.annotation.Documented;
    024    import java.lang.annotation.Retention;
    025    import java.lang.annotation.Target;
    026
    027    import org.apache.tapestry5.ioc.annotations.UseWith;
    028    import org.apache.tapestry5.services.javascript.JavaScriptSupport;
    029
    030    /**
    031     * Defines a field of a component class that is replaced at runtime with a read-only value obtained from the
    032     * {@link org.apache.tapestry5.services.Environment} service.
    033     * <p>
    034     * Most commonly, the field will be of type {@link JavaScriptSupport}, {@link org.apache.tapestry5.services.Heartbeat}
    035     * or {@link org.apache.tapestry5.services.FormSupport}, though many other options are possible.
    036     */
    037    @Target(FIELD)
    038    @Documented
    039    @Retention(RUNTIME)
    040    @UseWith(
    041    { COMPONENT, MIXIN, PAGE })
    042    public @interface Environmental
    043    {
    044        /**
    045         * The value determines if the environmental service to be injected is required or not. In most cases, it is, so the
    046         * default is true.
    047         */
    048        boolean value() default true;
    049    }