@ConfigurationProperties(prefix = "spring.mvc")
public class WebMvcProperties {

	public static class View {
		/**
		 * Spring MVC view prefix.  前綴
		 */
		private String prefix;
		/**
		 * Spring MVC view suffix.  后綴
		 */
		private String suffix;

protected Resource getResource(HttpServletRequest request) throws IOException {
		String path = (String) request.getAttribute(HandlerMapping.PATH_WITHIN_HANDLER_MAPPING_ATTRIBUTE);
		if (path == null) {
			throw new IllegalStateException("Required request attribute '" +
					HandlerMapping.PATH_WITHIN_HANDLER_MAPPING_ATTRIBUTE + "' is not set");
		}
		path = processPath(path);
		if (!StringUtils.hasText(path) || isInvalidPath(path)) {
			if (logger.isTraceEnabled()) {
				logger.trace("Ignoring invalid resource path [" + path + "]");
			}
			return null;
		}
		if (isInvalidEncodedPath(path)) {
			if (logger.isTraceEnabled()) {
				logger.trace("Ignoring invalid resource path with escape sequences [" + path + "]");
			}
			return null;
		}
		ResourceResolverChain resolveChain = new DefaultResourceResolverChain(getResourceResolvers());
        //重點關注此處
		Resource resource = resolveChain.resolveResource(request, path, getLocations());
		if (resource == null || getResourceTransformers().isEmpty()) {
			return resource;
		}
		ResourceTransformerChain transformChain =
				new DefaultResourceTransformerChain(resolveChain, getResourceTransformers());
		resource = transformChain.transform(request, resource);
		return resource;
	}

@ConfigurationProperties(prefix = "spring.resources", ignoreUnknownFields = false)
public class ResourceProperties {
	private static final String[] CLASSPATH_RESOURCE_LOCATIONS = {
			"classpath:/META-INF/resources/", "classpath:/resources/",
			"classpath:/static/", "classpath:/public/" };
	/**
	 * Locations of static resources. Defaults to classpath:[/META-INF/resources/,
	 * /resources/, /static/, /public/].
	 */
	private String[] staticLocations = CLASSPATH_RESOURCE_LOCATIONS;

@Controller
public class PageApi {
    @GetMapping({"/", "/index"})
    public String toPage(String id){
        return "index";
    }
}