code: public final String getApiMessageId() {
  
          if (TraceComponent.isAnyTracingEnabled() && tc.isEntryEnabled())
              SibTr.entry(this, tc, "getApiMessageId");
  
          String value = null;
  
          /* The ApiMessageId is held as hexBinary & so we need to convert to an */
          /* ID:xxxx format. */
          byte[] binValue = (byte[]) getApi().getField(JsApiAccess.MESSAGEID);
          if (binValue != null) {
              /* It'll be more economical to get the length right immediately */
              StringBuffer sbuf = new StringBuffer((binValue.length * 2) + 3);
  
              /* Insert the ID: then add on the binary value as a hex string */
              sbuf.append(ID_STRING);
              HexString.binToHex(binValue, 0, binValue.length, sbuf);
  
              /* Return the String representation */
              value = sbuf.toString();
          }
  
          if (TraceComponent.isAnyTracingEnabled() && tc.isEntryEnabled())
              SibTr.exit(this, tc, "getApiMessageId", value);
  
          return value;
      }
docs: /*
  Get the contents of the ApiMessageId field from the message header.
  
  Javadoc description supplied by JsApiMessage interface.