ConditionalOnSingleCandidate Type — spring-boot Architecture

Source Code

core/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/condition/ConditionalOnSingleCandidate.java lines 48–100

@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 matches if a bean of
	 * the class specified is contained in the {@link BeanFactory} and a primary candidate
	 * exists in case of multiple instances. Beans that are not autowire candidates, that
	 * are not default candidates, or that are fallback candidates are ignored.
	 * <p>
	 * Since this annotation is parsed by loading class bytecode, it is safe to specify
	 * classes here that may ultimately not be on the classpath, but only if this
	 * annotation is directly on the affected component and <b>not</b> if this annotation
	 * is used as a composed, meta-annotation. In order to use this annotation as a
	 * meta-annotation, only use the {@link #type} attribute.
	 * <p>
	 * This attribute may <strong>not</strong> 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
	 * @see Bean#autowireCandidate()
	 * @see BeanDefinition#isAutowireCandidate
	 * @see Bean#defaultCandidate()
	 * @see AbstractBeanDefinition#isDefaultCandidate
	 */
	Class<?> value() default Object.class;

	/**
	 * The class type name of bean that should be checked. The condition matches if a bean
	 * of the class specified is contained in the {@link BeanFactory} and a primary
	 * candidate exists in case of multiple instances. Beans that are not autowire
	 * candidates, that are not default candidates, or that are fallback candidates are
	 * ignored.
	 * <p>
	 * This attribute may <strong>not</strong> 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
	 * @see Bean#autowireCandidate()
	 * @see BeanDefinition#isAutowireCandidate
	 * @see Bean#defaultCandidate()
	 * @see AbstractBeanDefinition#isDefaultCandidate
	 */
	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;

}