Configurations Class — spring-boot Architecture

Source Code

core/spring-boot/src/main/java/org/springframework/boot/context/annotation/Configurations.java lines 61–189

public abstract class Configurations {

	private static final Comparator<Object> COMPARATOR = OrderComparator.INSTANCE
		.thenComparing((other) -> other.getClass().getName());

	private final @Nullable UnaryOperator<Collection<Class<?>>> sorter;

	private final Set<Class<?>> classes;

	private final @Nullable Function<Class<?>, String> beanNameGenerator;

	/**
	 * Create a new {@link Configurations} instance.
	 * @param classes the configuration classes
	 */
	protected Configurations(Collection<Class<?>> classes) {
		Assert.notNull(classes, "'classes' must not be null");
		this.sorter = null;
		this.classes = Collections.unmodifiableSet(new LinkedHashSet<>(classes));
		this.beanNameGenerator = null;
	}

	/**
	 * Create a new {@link Configurations} instance.
	 * @param sorter a {@link UnaryOperator} used to sort the configurations
	 * @param classes the configuration classes
	 * @param beanNameGenerator an optional function used to generate the bean name
	 * @since 3.4.0
	 */
	protected Configurations(@Nullable UnaryOperator<Collection<Class<?>>> sorter, Collection<Class<?>> classes,
			@Nullable Function<Class<?>, String> beanNameGenerator) {
		Assert.notNull(classes, "'classes' must not be null");
		this.sorter = (sorter != null) ? sorter : UnaryOperator.identity();
		Collection<Class<?>> sorted = this.sorter.apply(classes);
		this.classes = Collections.unmodifiableSet(new LinkedHashSet<>(sorted));
		this.beanNameGenerator = beanNameGenerator;
	}

	protected final Set<Class<?>> getClasses() {
		return this.classes;
	}

	/**
	 * Merge configurations from another source of the same type.
	 * @param other the other {@link Configurations} (must be of the same type as this
	 * instance)
	 * @return a new configurations instance (must be of the same type as this instance)
	 */
	protected Configurations merge(Configurations other) {
		Set<Class<?>> mergedClasses = new LinkedHashSet<>(getClasses());
		mergedClasses.addAll(other.getClasses());
		if (this.sorter != null) {
			mergedClasses = new LinkedHashSet<>(this.sorter.apply(mergedClasses));
		}
		return merge(mergedClasses);
	}

	/**
	 * Merge configurations.
	 * @param mergedClasses the merged classes
	 * @return a new configurations instance (must be of the same type as this instance)
	 */
	protected abstract Configurations merge(Set<Class<?>> mergedClasses);

	/**
	 * Return the bean name that should be used for the given configuration class or
	 * {@code null} to use the default name.
	 * @param beanClass the bean class
	 * @return the bean name
	 * @since 3.4.0
	 */
	public @Nullable String getBeanName(Class<?> beanClass) {
		return (this.beanNameGenerator != null) ? this.beanNameGenerator.apply(beanClass) : null;
	}

	/**
	 * Return the classes from all the specified configurations in the order that they
	 * would be registered.
	 * @param configurations the source configuration
	 * @return configuration classes in registration order
	 */
	public static Class<?>[] getClasses(Configurations... configurations) {
		return getClasses(Arrays.asList(configurations));
	}

	/**
	 * Return the classes from all the specified configurations in the order that they
	 * would be registered.
	 * @param configurations the source configuration
	 * @return configuration classes in registration order
	 */
	public static Class<?>[] getClasses(Collection<Configurations> configurations) {
		List<Configurations> collated = collate(configurations);
		LinkedHashSet<Class<?>> classes = collated.stream()
			.flatMap(Configurations::streamClasses)
			.collect(Collectors.toCollection(LinkedHashSet::new));
		return ClassUtils.toClassArray(classes);
	}

	/**
	 * Collate the given configuration by sorting and merging them.
	 * @param configurations the source configuration
	 * @return the collated configurations
	 * @since 3.4.0
	 */
	public static List<Configurations> collate(Collection<Configurations> configurations) {
		LinkedList<Configurations> collated = new LinkedList<>();
		for (Configurations configuration : sortConfigurations(configurations)) {
			if (collated.isEmpty() || collated.getLast().getClass() != configuration.getClass()) {
				collated.add(configuration);
			}
			else {
				collated.set(collated.size() - 1, collated.getLast().merge(configuration));
			}
		}
		return collated;
	}

	private static List<Configurations> sortConfigurations(Collection<Configurations> configurations) {
		List<Configurations> sorted = new ArrayList<>(configurations);
		sorted.sort(COMPARATOR);
		return sorted;
	}

	private static Stream<Class<?>> streamClasses(Configurations configurations) {
		return configurations.getClasses().stream();
	}

}