this();  this.ds = ds;  this.tm = tm;
subscriptions = new ConcurrentReaderHashMap();  queues = new ConcurrentReaderHashMap();  topics = new ConcurrentReaderHashMap();  idMap = new ConcurrentReaderHashMap();  sqlProperties = new Properties();  populateTables = new ArrayList();
   public JDBCChannelMapper(DataSource ds, TransactionManager tm)   {      this();      this.ds = ds;      this.tm = tm;   }