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}