001/* 002 * Copyright 2012-2017 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 * http://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.boot.autoconfigure.condition; 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.context.annotation.Conditional; 026 027/** 028 * Configuration annotation for a conditional element that depends on the value of a SpEL 029 * expression. 030 * 031 * @author Dave Syer 032 */ 033@Retention(RetentionPolicy.RUNTIME) 034@Target({ ElementType.TYPE, ElementType.METHOD }) 035@Documented 036@Conditional(OnExpressionCondition.class) 037public @interface ConditionalOnExpression { 038 039 /** 040 * The SpEL expression to evaluate. Expression should return {@code true} if the 041 * condition passes or {@code false} if it fails. 042 * @return the SpEL expression 043 */ 044 String value() default "true"; 045 046}