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}