SystemEnvironmentConfigDataLocationResolver Class — spring-boot Architecture

Source Code

core/spring-boot/src/main/java/org/springframework/boot/context/config/SystemEnvironmentConfigDataLocationResolver.java lines 34–97

class SystemEnvironmentConfigDataLocationResolver
		implements ConfigDataLocationResolver<SystemEnvironmentConfigDataResource> {

	private static final String PREFIX = "env:";

	private static final String DEFAULT_EXTENSION = ".properties";

	private final List<PropertySourceLoader> loaders;

	private final Function<String, @Nullable String> environment;

	SystemEnvironmentConfigDataLocationResolver() {
		this.loaders = SpringFactoriesLoader.loadFactories(PropertySourceLoader.class, getClass().getClassLoader());
		this.environment = System::getenv;
	}

	SystemEnvironmentConfigDataLocationResolver(List<PropertySourceLoader> loaders,
			Function<String, @Nullable String> environment) {
		this.loaders = loaders;
		this.environment = environment;
	}

	@Override
	public boolean isResolvable(ConfigDataLocationResolverContext context, ConfigDataLocation location) {
		return location.hasPrefix(PREFIX);
	}

	@Override
	public List<SystemEnvironmentConfigDataResource> resolve(ConfigDataLocationResolverContext context,
			ConfigDataLocation location)
			throws ConfigDataLocationNotFoundException, ConfigDataResourceNotFoundException {
		String value = location.getNonPrefixedValue(PREFIX);
		FileHint fileHint = FileHint.from(value);
		String variableName = FileHint.removeFrom(value);
		PropertySourceLoader loader = getLoader(fileHint.getExtensionOrElse(DEFAULT_EXTENSION));
		if (hasEnvVariable(variableName)) {
			return List.of(new SystemEnvironmentConfigDataResource(variableName, loader, this.environment,
					fileHint.getEncodingAsCharset()));
		}
		if (location.isOptional()) {
			return Collections.emptyList();
		}
		throw new ConfigDataLocationNotFoundException(location,
				"Environment variable '%s' is not set".formatted(variableName), null);
	}

	private PropertySourceLoader getLoader(String extension) {
		extension = (!extension.startsWith(".")) ? extension : extension.substring(1);
		for (PropertySourceLoader loader : this.loaders) {
			for (String supportedExtension : loader.getFileExtensions()) {
				if (supportedExtension.equalsIgnoreCase(extension)) {
					return loader;
				}
			}
		}
		throw new IllegalStateException(
				"File extension '%s' is not known to any PropertySourceLoader".formatted(extension));
	}

	private boolean hasEnvVariable(String variableName) {
		return this.environment.apply(variableName) != null;
	}

}