SourcesIterator Class — spring-boot Architecture

Source Code

core/spring-boot/src/main/java/org/springframework/boot/context/properties/source/SpringConfigurationPropertySources.java lines 79–140

	private static class SourcesIterator implements Iterator<ConfigurationPropertySource> {

		private final Deque<Iterator<PropertySource<?>>> iterators;

		private @Nullable ConfigurationPropertySource next;

		private final Function<PropertySource<?>, ConfigurationPropertySource> adapter;

		SourcesIterator(Iterator<PropertySource<?>> iterator,
				Function<PropertySource<?>, ConfigurationPropertySource> adapter) {
			this.iterators = new ArrayDeque<>(4);
			this.iterators.push(iterator);
			this.adapter = adapter;
		}

		@Override
		public boolean hasNext() {
			return fetchNext() != null;
		}

		@Override
		public ConfigurationPropertySource next() {
			ConfigurationPropertySource next = fetchNext();
			if (next == null) {
				throw new NoSuchElementException();
			}
			this.next = null;
			return next;
		}

		private @Nullable ConfigurationPropertySource fetchNext() {
			if (this.next == null) {
				if (this.iterators.isEmpty()) {
					return null;
				}
				if (!this.iterators.peek().hasNext()) {
					this.iterators.pop();
					return fetchNext();
				}
				PropertySource<?> candidate = this.iterators.peek().next();
				if (candidate.getSource() instanceof ConfigurableEnvironment configurableEnvironment) {
					push(configurableEnvironment);
					return fetchNext();
				}
				if (isIgnored(candidate)) {
					return fetchNext();
				}
				this.next = this.adapter.apply(candidate);
			}
			return this.next;
		}

		private void push(ConfigurableEnvironment environment) {
			this.iterators.push(environment.getPropertySources().iterator());
		}

		private boolean isIgnored(PropertySource<?> candidate) {
			return (candidate instanceof StubPropertySource
					|| candidate instanceof ConfigurationPropertySourcesPropertySource);
		}

	}