@Override
    public void open(int taskNumber, int numTasks) throws IOException {
        synchronized (JDBCUpsertOutputFormat.class) {
            if (resourceCheck) {
                resourceCheck = false;
                JdbcResourceCheck.getInstance().checkResourceStatus(this.checkProperties);
            }
        }
        openJdbc();
    }
Connects to the target database and initializes the prepared statement.

@param taskNumber The number of the parallel instance.
@throws IOException Thrown, if the output could not be opened due to an
                    I/O problem.
rdb/rdb-sink/src/main/java/com/dtstack/flink/sql/sink/rdb/format/JDBCUpsertOutputFormat.java