private ConfigurableEnvironment prepareEnvironment(SpringApplicationRunListeners listeners,

            ApplicationArguments applicationArguments) {

        // Create and configure the environment

        ConfigurableEnvironment environment = getOrCreateEnvironment();

        configureEnvironment(environment, applicationArguments.getSourceArgs());

        listeners.environmentPrepared(environment);

        bindToSpringApplication(environment);

        if (!this.isCustomEnvironment) {

            environment = new EnvironmentConverter(getClassLoader()).convertEnvironmentIfNecessary(environment,

                    deduceEnvironmentClass());

        }

        ConfigurationPropertySources.attach(environment);

        return environment;

    }

private static final String DEFAULT_PROPERTIES = "defaultProperties";

    // Note the order is from least to most specific (last one wins)

    private static final String DEFAULT_SEARCH_LOCATIONS = "classpath:/,classpath:/config/,file:./,file:./config/";

    private static final String DEFAULT_NAMES = "application";

    private static final Set<String> NO_SEARCH_NAMES = Collections.singleton(null);

    private static final Bindable<String[]> STRING_ARRAY = Bindable.of(String[].class);

    /**

     * The "active profiles" property name.

     */

    public static final String ACTIVE_PROFILES_PROPERTY = "spring.profiles.active";

    /**

     * The "includes profiles" property name.

     */

    public static final String INCLUDE_PROFILES_PROPERTY = "spring.profiles.include";

    /**

     * The "config name" property name.

     */

    public static final String CONFIG_NAME_PROPERTY = "spring.config.name";

    /**

     * The "config location" property name.

     */

    public static final String CONFIG_LOCATION_PROPERTY = "spring.config.location";

public class YamlPropertySourceLoader implements PropertySourceLoader {

    @Override

    public String[] getFileExtensions() {

        return new String[] { "yml", "yaml" };

    }

    @Override

    public List<PropertySource<?>> load(String name, Resource resource) throws IOException {

        if (!ClassUtils.isPresent("org.yaml.snakeyaml.Yaml", null)) {

            throw new IllegalStateException(

                    "Attempted to load " + name + " but snakeyaml was not found on the classpath");

        }

        List<Map<String, Object>> loaded = new OriginTrackedYamlLoader(resource).load();

        if (loaded.isEmpty()) {

            return Collections.emptyList();

        }

        List<PropertySource<?>> propertySources = new ArrayList<>(loaded.size());

        for (int i = 0; i < loaded.size(); i++) {

            String documentNumber = (loaded.size() != 1) ? " (document #" + i + ")" : "";

            propertySources.add(new OriginTrackedMapPropertySource(name + documentNumber, loaded.get(i)));

        }

        return propertySources;

    }

}