code: public void setDefaultTransactionIsolation(final int transactionIsolation) {
  		if (Connection.TRANSACTION_READ_UNCOMMITTED == transactionIsolation
  				|| Connection.TRANSACTION_READ_COMMITTED == transactionIsolation
  				|| Connection.TRANSACTION_REPEATABLE_READ == transactionIsolation
  				|| Connection.TRANSACTION_SERIALIZABLE == transactionIsolation) {
  			props.put(PROPS_TRANSACTION_ISOLATION, String.valueOf(transactionIsolation));
  		} else {
  			throw new IllegalArgumentException("Unsupported level [" + transactionIsolation + "]");
  		}
  	}
docs: transactionIsolationオプションの指定
  
  @see Connection#TRANSACTION_READ_UNCOMMITTED
  @see Connection#TRANSACTION_READ_COMMITTED
  @see Connection#TRANSACTION_REPEATABLE_READ
  @see Connection#TRANSACTION_SERIALIZABLE
  
  @param transactionIsolation transactionIsolationオプション