code: public Message setObject(Object obj) {
          if(obj == null) return this;
          if(obj instanceof byte[])
              return setBuffer((byte[])obj);
          if(obj instanceof Buffer)
              return setBuffer((Buffer)obj);
          try {
              return setBuffer(Util.objectToByteBuffer(obj));
          }
          catch(Exception ex) {
              throw new IllegalArgumentException(ex);
          }
      }
docs: Takes an object and uses Java serialization to generate the byte[] buffer which is set in the
  message. Parameter 'obj' has to be serializable (e.g. implementing Serializable,
  Externalizable or Streamable, or be a basic type (e.g. Integer, Short etc)).