jdbc-protolib/src/main/java/com/streamsets/pipeline/lib/jdbc/JdbcBaseRecordWriter.java
private void createCustomFieldMappings() {
    for (JdbcFieldColumnParamMapping mapping : customMappings) {
      LOG.debug("Custom mapping field {} to column {}", mapping.field, mapping.columnName);
      if (columnsToFields.containsKey(mapping.columnName)) {
        LOG.debug("Mapping field {} to column {}", mapping.field, mapping.columnName);
        columnsToFields.put(mapping.columnName, mapping.field);
        columnsToParameters.put(mapping.columnName, mapping.paramValue);
      }
    }
  }
private void createCustomFieldMappings() {
    for (JdbcFieldColumnParamMapping mapping : customMappings) {
      LOG.debug("Custom mapping field {} to column {}", mapping.field, mapping.columnName);
      if (columnsToFields.containsKey(mapping.columnName)) {
        LOG.debug("Mapping field {} to column {}", mapping.field, mapping.columnName);
        columnsToFields.put(mapping.columnName, mapping.field);
        columnsToParameters.put(mapping.columnName, mapping.paramValue);
      }
    }
  }
Use "Field to Column Mapping" option obtained from configuration and update
columnsToFields and columnsToParameters.