AggregateBinder Class — spring-boot Architecture

Source Code

core/spring-boot/src/main/java/org/springframework/boot/context/properties/bind/AggregateBinder.java lines 34–121

abstract class AggregateBinder<T> {

	private final Context context;

	AggregateBinder(Context context) {
		this.context = context;
	}

	/**
	 * Determine if recursive binding is supported.
	 * @param source the configuration property source or {@code null} for all sources.
	 * @return if recursive binding is supported
	 */
	protected abstract boolean isAllowRecursiveBinding(@Nullable ConfigurationPropertySource source);

	/**
	 * Perform binding for the aggregate.
	 * @param name the configuration property name to bind
	 * @param target the target to bind
	 * @param elementBinder an element binder
	 * @return the bound aggregate or null
	 */
	@SuppressWarnings("unchecked")
	final @Nullable Object bind(ConfigurationPropertyName name, Bindable<?> target,
			AggregateElementBinder elementBinder) {
		Object result = bindAggregate(name, target, elementBinder);
		Supplier<?> value = target.getValue();
		if (result == null || value == null) {
			return result;
		}
		return merge((Supplier<T>) value, (T) result);
	}

	/**
	 * Perform the actual aggregate binding.
	 * @param name the configuration property name to bind
	 * @param target the target to bind
	 * @param elementBinder an element binder
	 * @return the bound result
	 */
	protected abstract @Nullable Object bindAggregate(ConfigurationPropertyName name, Bindable<?> target,
			AggregateElementBinder elementBinder);

	/**
	 * Merge any additional elements into the existing aggregate.
	 * @param existing the supplier for the existing value
	 * @param additional the additional elements to merge
	 * @return the merged result
	 */
	protected abstract T merge(Supplier<T> existing, T additional);

	/**
	 * Return the context being used by this binder.
	 * @return the context
	 */
	protected final Context getContext() {
		return this.context;
	}

	/**
	 * Internal class used to supply the aggregate and cache the value.
	 *
	 * @param <T> the aggregate type
	 */
	protected static class AggregateSupplier<T> {

		private final Supplier<T> supplier;

		private @Nullable T supplied;

		public AggregateSupplier(Supplier<T> supplier) {
			this.supplier = supplier;
		}

		public T get() {
			if (this.supplied == null) {
				this.supplied = this.supplier.get();
			}
			return this.supplied;
		}

		public boolean wasSupplied() {
			return this.supplied != null;
		}

	}

}