@Override
    @SuppressWarnings("unchecked")
    protected <T> HasDelegate<T> resolveDelegateFrom(Input input)
            throws IOException
    {
        final String className = input.readString();

        final HasDelegate<T> hd = (HasDelegate<T>) delegateMapping
                .get(className);
        if (hd == null)
            throw new UnknownTypeException("delegate: " + className
                    + " (Outdated registry)");

        return hd;
    }
Used by {@link RuntimeSchema#map(Class, Class)}.
protostuff-runtime/src/main/java/io/protostuff/runtime/DefaultIdStrategy.java