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.ioc.annotations.UseWith;
016import org.apache.tapestry5.services.javascript.JavaScriptSupport;
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 * Defines a field of a component class that is replaced at runtime with a read-only value obtained from the
028 * {@link org.apache.tapestry5.services.Environment} service.
029 *
030 * Most commonly, the field will be of type {@link JavaScriptSupport}, {@link org.apache.tapestry5.services.Heartbeat}
031 * or {@link org.apache.tapestry5.services.FormSupport}, though many other options are possible.
032 */
033@Target(FIELD)
034@Documented
035@Retention(RUNTIME)
036@UseWith(
037{ COMPONENT, MIXIN, PAGE })
038public @interface Environmental
039{
040    /**
041     * The value determines if the environmental service to be injected is required or not. In most cases, it is, so the
042     * default is true.
043     */
044    boolean value() default true;
045}