alibaba/ARouter · error · HandlerException

Extract the default group failed, the path must be start wit

Error message

Extract the default group failed, the path must be start with '/' and contain more than 2 '/'!

What it means

extractGroup derives the route group (the segment between the first and second '/') from a path. ARouter throws HandlerException when the path is empty or does not start with '/', because the documented path convention '/group/xxx' cannot be parsed.

Source

Thrown at arouter-api/src/main/java/com/alibaba/android/arouter/launcher/_ARouter.java:245

     * Check route availability without navigating to the destination.
     */
    protected boolean hasRoute(String path) {
        final Postcard postcard;
        try {
            postcard = build(path);
        } catch (HandlerException invalidPath) {
            return false;
        }

        return LogisticsCenter.hasRoute(postcard);
    }

    /**
     * Extract the default group from path.
     */
    private String extractGroup(String path) {
        if (TextUtils.isEmpty(path) || !path.startsWith("/")) {
            throw new HandlerException(Consts.TAG + "Extract the default group failed, the path must be start with '/' and contain more than 2 '/'!");
        }

        try {
            String defaultGroup = path.substring(1, path.indexOf("/", 1));
            if (TextUtils.isEmpty(defaultGroup)) {
                throw new HandlerException(Consts.TAG + "Extract the default group failed! There's nothing between 2 '/'!");
            } else {
                return defaultGroup;
            }
        } catch (Exception e) {
            logger.warning(Consts.TAG, "Failed to extract default group! " + e.getMessage());
            return null;
        }
    }

    static void afterInit() {
        // Trigger interceptor init, use byName.
        interceptorService = (InterceptorService) ARouter.getInstance().build("/arouter/service/interceptor").navigation();

View on GitHub (pinned to 84f451d244)

Solutions

1. Ensure every route path starts with '/' and contains at least two slashes: '/group/path'
2. Normalize external input before building, e.g. prepend '/' when missing
3. Register routes with the same convention used at lookup time
4. Prefer the two-segment form and validate with a regex ^/[A-Za-z0-9_]+/.+

Example fix

// before
ARouter.getInstance().build("user/login").navigation(); // HandlerException
// after
String path = "user/login";
if (!path.startsWith("/")) path = "/" + path;
ARouter.getInstance().build(path).navigation();

private static final Pattern ROUTE = Pattern.compile("^/[A-Za-z0-9_]+/.+");
public static boolean isValidRoutePath(String p) {
    return p != null && ROUTE.matcher(p).matches();
}

try {
    ARouter.getInstance().build(path).navigation();
} catch (HandlerException e) {
    Log.w(TAG, "Path must look like /group/xxx", e);
}

When it happens

Trigger: Calling build("user/login") (missing leading slash), build(""), or hasRoute with such a path; passing a full URI string ('http://...') where a path is expected.

Common situations: Routes stored without the leading slash in config files; users passing package/class names instead of route paths; paths generated by concatenation losing the '/'; deep-link URL host+path mixed up.

Understand the failure class

Background: "Invalid ... format", "must be in format X", "does not look like a ..." — invalid argument format errors across CLI tools and libraries — this error's family across 17 libraries.

Related errors

• Extract the default group failed! There's nothing between 2
• ARouter::Init::Invoke init(context) first!
• ARouterCore::Init::Invoke init(context) first!
• Parameter is invalid!
• Parameter invalid!

AI-assisted analysis of alibaba/ARouter@84f451d244 (2026-09-06). Data as JSON: /api/errors/856aa515ef1bded6. Report an issue: GitHub.