lodsve.core.condition.ConditionalOnSingleCandidate Maven / Gradle / Ivy
/*
* Copyright 2012-2017 the original author or authors.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package lodsve.core.condition;
import org.springframework.beans.factory.BeanFactory;
import org.springframework.context.ApplicationContext;
import org.springframework.context.annotation.Conditional;
import java.lang.annotation.Documented;
import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;
/**
* {@link Conditional} that only matches when the specified bean class is already
* contained in the {@link BeanFactory} and a single candidate can be determined.
*
* The condition will also match if multiple matching bean instances are already contained
* in the {@link BeanFactory} but a primary candidate has been defined; essentially, the
* condition match if auto-wiring a bean with the defined type will succeed.
*
* The condition can only match the bean definitions that have been processed by the
* application context so far and, as such, it is strongly recommended to use this
* condition on auto-configuration classes only. If a candidate bean may be created by
* another auto-configuration, make sure that the one using this condition runs after.
*
* @author Stephane Nicoll
* @since 1.3.0
*/
@Target({ ElementType.TYPE, ElementType.METHOD })
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Conditional(OnBeanCondition.class)
public @interface ConditionalOnSingleCandidate {
/**
* The class type of bean that should be checked. The condition match if the class
* specified is contained in the {@link ApplicationContext} and a primary candidate
* exists in case of multiple instances.
*
* This attribute may not be used in conjunction with
* {@link #type()}, but it may be used instead of {@link #type()}.
* @return the class type of the bean to check
*/
Class value() default Object.class;
/**
* The class type name of bean that should be checked. The condition matches if the
* class specified is contained in the {@link ApplicationContext} and a primary
* candidate exists in case of multiple instances.
*
* This attribute may not be used in conjunction with
* {@link #value()}, but it may be used instead of {@link #value()}.
* @return the class type name of the bean to check
*/
String type() default "";
/**
* Strategy to decide if the application context hierarchy (parent contexts) should be
* considered.
* @return the search strategy
*/
SearchStrategy search() default SearchStrategy.ALL;
}