SingleCandidateSpec Class — spring-boot Architecture

Source Code

core/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/condition/OnBeanCondition.java lines 806–828

	private static class SingleCandidateSpec extends Spec<ConditionalOnSingleCandidate> {

		private static final Collection<String> FILTERED_TYPES = Arrays.asList("", Object.class.getName());

		SingleCandidateSpec(ConditionContext context, AnnotatedTypeMetadata metadata, MergedAnnotations annotations) {
			super(context, metadata, annotations, ConditionalOnSingleCandidate.class);
		}

		@Override
		protected Set<String> extractTypes(@Nullable MultiValueMap<String, @Nullable Object> attributes) {
			Set<String> types = super.extractTypes(attributes);
			types.removeAll(FILTERED_TYPES);
			return types;
		}

		@Override
		protected void validate(@Nullable BeanTypeDeductionException ex) {
			Assert.isTrue(getTypes().size() == 1,
					() -> getAnnotationName() + " annotations must specify only one type (got "
							+ StringUtils.collectionToCommaDelimitedString(getTypes()) + ")");
		}

	}