    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 static java.lang.annotation.ElementType.FIELD;
    018import static java.lang.annotation.RetentionPolicy.RUNTIME;
    019import static org.apache.tapestry5.ioc.annotations.AnnotationUseContext.COMPONENT;
    020import static org.apache.tapestry5.ioc.annotations.AnnotationUseContext.MIXIN;
    021import static org.apache.tapestry5.ioc.annotations.AnnotationUseContext.PAGE;
    022
    023import java.lang.annotation.Documented;
    024import java.lang.annotation.Retention;
    025import java.lang.annotation.Target;
    026
    027import org.apache.tapestry5.ioc.annotations.UseWith;
    028import 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 })
    042public @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}