PropertySourcesPlaceholdersResolver Class — spring-boot Architecture

Source Code

core/spring-boot/src/main/java/org/springframework/boot/context/properties/bind/PropertySourcesPlaceholdersResolver.java lines 36–86

public class PropertySourcesPlaceholdersResolver implements PlaceholdersResolver {

	private final @Nullable Iterable<PropertySource<?>> sources;

	private final PropertyPlaceholderHelper helper;

	public PropertySourcesPlaceholdersResolver(Environment environment) {
		this(getSources(environment), null);
	}

	public PropertySourcesPlaceholdersResolver(@Nullable Iterable<PropertySource<?>> sources) {
		this(sources, null);
	}

	public PropertySourcesPlaceholdersResolver(@Nullable Iterable<PropertySource<?>> sources,
			@Nullable PropertyPlaceholderHelper helper) {
		this.sources = sources;
		this.helper = (helper != null) ? helper
				: new PropertyPlaceholderHelper(SystemPropertyUtils.PLACEHOLDER_PREFIX,
						SystemPropertyUtils.PLACEHOLDER_SUFFIX, SystemPropertyUtils.VALUE_SEPARATOR,
						SystemPropertyUtils.ESCAPE_CHARACTER, true);
	}

	@Override
	public @Nullable Object resolvePlaceholders(@Nullable Object value) {
		if (value instanceof String string) {
			return this.helper.replacePlaceholders(string, this::resolvePlaceholder);
		}
		return value;
	}

	protected @Nullable String resolvePlaceholder(String placeholder) {
		if (this.sources != null) {
			for (PropertySource<?> source : this.sources) {
				Object value = source.getProperty(placeholder);
				if (value != null) {
					return String.valueOf(value);
				}
			}
		}
		return null;
	}

	private static PropertySources getSources(Environment environment) {
		Assert.notNull(environment, "'environment' must not be null");
		Assert.isInstanceOf(ConfigurableEnvironment.class, environment,
				"'environment' must be a ConfigurableEnvironment");
		return ((ConfigurableEnvironment) environment).getPropertySources();
	}

}