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}