@Override
    public void addField(Field<?> field)
    {
        if (field.number < 1)
        {
            throw new IllegalArgumentException("Invalid field number " + field.number
                    + " from field " + field.name);
        }

        if (fields.put(field.name, field) != null)
            throw err("Duplicate message field: " + field.name, getProto());
    }
Represents the message defined in the {@link Proto}.

@author David Yu
@created Dec 19, 2009
protostuff-parser/src/main/java/io/protostuff/parser/Message.java