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.Annotation;
020import java.lang.annotation.Documented;
021import java.lang.annotation.ElementType;
022import java.lang.annotation.Retention;
023import java.lang.annotation.RetentionPolicy;
024import java.lang.annotation.Target;
025
026import org.springframework.beans.factory.BeanFactory;
027import org.springframework.context.ApplicationContext;
028import org.springframework.context.annotation.Conditional;
029
030/**
031 * {@link Conditional} that only matches when the specified bean classes and/or names are
032 * already contained in the {@link BeanFactory}. When placed on a {@code @Bean} method,
033 * the bean class defaults to the return type of the factory method:
034 *
035 * <pre class="code">
036 * &#064;Configuration
037 * public class MyAutoConfiguration {
038 *
039 *     &#064;ConditionalOnBean
040 *     &#064;Bean
041 *     public MyService myService() {
042 *         ...
043 *     }
044 *
045 * }</pre>
046 * <p>
047 * In the sample above the condition will match if a bean of type {@code MyService} is
048 * already contained in the {@link BeanFactory}.
049 * <p>
050 * The condition can only match the bean definitions that have been processed by the
051 * application context so far and, as such, it is strongly recommended to use this
052 * condition on auto-configuration classes only. If a candidate bean may be created by
053 * another auto-configuration, make sure that the one using this condition runs after.
054 *
055 * @author Phillip Webb
056 */
057@Target({ ElementType.TYPE, ElementType.METHOD })
058@Retention(RetentionPolicy.RUNTIME)
059@Documented
060@Conditional(OnBeanCondition.class)
061public @interface ConditionalOnBean {
062
063        /**
064         * The class type of bean that should be checked. The condition matches when any of
065         * the classes specified is contained in the {@link ApplicationContext}.
066         * @return the class types of beans to check
067         */
068        Class<?>[] value() default {};
069
070        /**
071         * The class type names of bean that should be checked. The condition matches when any
072         * of the classes specified is contained in the {@link ApplicationContext}.
073         * @return the class type names of beans to check
074         */
075        String[] type() default {};
076
077        /**
078         * The annotation type decorating a bean that should be checked. The condition matches
079         * when any of the annotations specified is defined on a bean in the
080         * {@link ApplicationContext}.
081         * @return the class-level annotation types to check
082         */
083        Class<? extends Annotation>[] annotation() default {};
084
085        /**
086         * The names of beans to check. The condition matches when any of the bean names
087         * specified is contained in the {@link ApplicationContext}.
088         * @return the name of beans to check
089         */
090        String[] name() default {};
091
092        /**
093         * Strategy to decide if the application context hierarchy (parent contexts) should be
094         * considered.
095         * @return the search strategy
096         */
097        SearchStrategy search() default SearchStrategy.ALL;
098
099}