@Override
    protected CollectionSchema.MessageFactory getCollectionFactory(Class<?> clazz)
    {
        final RegisteredCollectionFactory rf = collectionMapping.get(clazz);
        if (rf == null)
        {
            if (clazz.getName().startsWith("java.util"))
                return CollectionSchema.MessageFactories.valueOf(clazz.getSimpleName());

            throw new UnknownTypeException("collection: " + clazz);
        }

        return rf;
    }
Register a {@link Delegate} and assign an id.
<p>
Delegate ids start at 1.
protostuff-runtime-registry/src/main/java/io/protostuff/runtime/ExplicitIdStrategy.java