001    // Copyright 2006 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 java.lang.annotation.Documented;
018    import static java.lang.annotation.ElementType.FIELD;
019    import java.lang.annotation.Retention;
020    import static java.lang.annotation.RetentionPolicy.RUNTIME;
021    import java.lang.annotation.Target;
022    
023    /**
024     * Defines a field of a component class that is replaced at runtime with a read-only value obtained from the {@link
025     * org.apache.tapestry5.services.Environment} service. <p>Most commonly, the field will be of type {@link
026     * org.apache.tapestry5.RenderSupport}, {@link org.apache.tapestry5.services.Heartbeat} or {@link
027     * org.apache.tapestry5.services.FormSupport}, though many other options are possible.
028     */
029    @Target(FIELD)
030    @Documented
031    @Retention(RUNTIME)
032    public @interface Environmental
033    {
034        /**
035         * The value determines if the environmental service to be injected is required or not. In most cases, it is, so the
036         * default is true.
037         */
038        boolean value() default true;
039    }