@Override
    @SuppressWarnings("unchecked")
    protected <T> HasSchema<T> writePojoIdTo(Output output, int fieldNumber, Class<T> clazz)
            throws IOException
    {
        final BaseHS<T> wrapper = (BaseHS<T>) pojoMapping.get(clazz);
        if (wrapper == null)
            throw new UnknownTypeException("pojo: " + clazz);

        output.writeUInt32(fieldNumber, wrapper.id, false);

        return wrapper;
    }
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