001/*
002 * Copyright 2002-2015 the original author or authors.
003 *
004 * Licensed under the Apache License, Version 2.0 (the "License");
005 * you may not use this file except in compliance with the License.
006 * You may obtain a copy of the License at
007 *
008 *      https://www.apache.org/licenses/LICENSE-2.0
009 *
010 * Unless required by applicable law or agreed to in writing, software
011 * distributed under the License is distributed on an "AS IS" BASIS,
012 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
013 * See the License for the specific language governing permissions and
014 * limitations under the License.
015 */
016
017package org.springframework.messaging.handler.annotation;
018
019import java.lang.annotation.Documented;
020import java.lang.annotation.ElementType;
021import java.lang.annotation.Retention;
022import java.lang.annotation.RetentionPolicy;
023import java.lang.annotation.Target;
024
025import org.springframework.core.annotation.AliasFor;
026
027/**
028 * Annotation which indicates that a method parameter should be bound to a message header.
029 *
030 * @author Rossen Stoyanchev
031 * @author Sam Brannen
032 * @since 4.0
033 */
034@Target(ElementType.PARAMETER)
035@Retention(RetentionPolicy.RUNTIME)
036@Documented
037public @interface Header {
038
039        /**
040         * Alias for {@link #name}.
041         */
042        @AliasFor("name")
043        String value() default "";
044
045        /**
046         * The name of the request header to bind to.
047         * @since 4.2
048         */
049        @AliasFor("value")
050        String name() default "";
051
052        /**
053         * Whether the header is required.
054         * <p>Default is {@code true}, leading to an exception if the header is
055         * missing. Switch this to {@code false} if you prefer a {@code null}
056         * value in case of a header missing.
057         * @see #defaultValue
058         */
059        boolean required() default true;
060
061        /**
062         * The default value to use as a fallback.
063         * <p>Supplying a default value implicitly sets {@link #required} to {@code false}.
064         */
065        String defaultValue() default ValueConstants.DEFAULT_NONE;
066
067}