001/* 002 * Copyright 2002-2012 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; 018 019/** 020 * Common annotation value constants. 021 * 022 * @author Rossen Stoyanchev 023 * @since 4.0 024 */ 025public interface ValueConstants { 026 027 /** 028 * Constant defining a value for no default - as a replacement for {@code null} which 029 * we cannot use in annotation attributes. 030 * <p>This is an artificial arrangement of 16 unicode characters, with its sole purpose 031 * being to never match user-declared values. 032 * @see Header#defaultValue() 033 */ 034 String DEFAULT_NONE = "\n\t\t\n\t\t\n\uE000\uE001\uE002\n\t\t\t\t\n"; 035 036}