public void readFrom(DataInput in) throws ClassNotFoundException, IOException {
    optionalFields = DataSerializer.readObject(in);
  }
Constructs a new instance with empty Properties. After construction the instance should
optionally invoke one or more "write" methods such as {@link #writeHostedLocators(Collection)}
before invoking <code>toData(DataOutput)</code> to marshal the Properties into the DataOutput
(onto the wire).
geode-core/src/main/java/org/apache/geode/distributed/internal/StartupMessageData.java