Method getGenericType

java/org/apache/tomcat/websocket/Util.java:175–243

(Class<T> type, Class<? extends T> clazz)

    private static <T> TypeResult getGenericType(Class<T> type, Class<? extends T> clazz) {

        // Look to see if this class implements the interface of interest

        // Get all the interfaces
        Type[] interfaces = clazz.getGenericInterfaces();
        for (Type iface : interfaces) {
            // Only need to check interfaces that use generics
            if (iface instanceof ParameterizedType pi) {
                // Look for the interface of interest
                if (pi.getRawType() instanceof Class) {
                    if (type.isAssignableFrom((Class<?>) pi.getRawType())) {
                        return getTypeParameter(clazz, pi.getActualTypeArguments()[0]);
                    }
                }
            }
        }

        // Interface not found on this class. Look at the superclass.
        @SuppressWarnings("unchecked")
        Class<? extends T> superClazz = (Class<? extends T>) clazz.getSuperclass();
        if (superClazz == null) {
            // Finished looking up the class hierarchy without finding anything
            throw new IllegalStateException();
        }

        TypeResult superClassTypeResult = getGenericType(type, superClazz);
        int dimension = superClassTypeResult.getDimension();
        if (superClassTypeResult.getIndex() == -1 && dimension == 0) {
            // Superclass implements interface and defines explicit type for
            // the interface of interest
            return superClassTypeResult;
        }

        if (superClassTypeResult.getIndex() > -1) {
            // Superclass implements interface and defines unknown type for
            // the interface of interest
            // Map that unknown type to the generic types defined in this class
            ParameterizedType superClassType = (ParameterizedType) clazz.getGenericSuperclass();
            TypeResult result =
                    getTypeParameter(clazz, superClassType.getActualTypeArguments()[superClassTypeResult.getIndex()]);
            result.incrementDimension(superClassTypeResult.getDimension());
            if (result.getClazz() != null && result.getDimension() > 0) {
                superClassTypeResult = result;
            } else {
                return result;
            }
        }

        if (superClassTypeResult.getDimension() > 0) {
            StringBuilder className = new StringBuilder();
            className.append("[".repeat(Math.max(0, dimension)));
            className.append('L');
            className.append(superClassTypeResult.getClazz().getCanonicalName());
            className.append(';');

            Class<?> arrayClazz;
            try {