Convert JDBC ResultSet into Ruby Hash with JRuby

jdbc_sample.rb

require './lib/adsjdbc-10.10.0.28.jar'
java_import java.sql.Driver
java_import java.sql.DriverManager
java_import 'com.extendedsystems.jdbc.advantage.ADSDriver'

class AdsAdapter

  def initialize(connect_string)
    @connect_string = connect_string
  end

  def establish_connection(connect_string = @connect_string)
    ::DriverManager.getConnection(connect_string)
  end

  def connection
    @connection ||= establish_connection
  end

  def execute(sql)
    stmt = connection.createStatement
    rs = stmt.executeQuery(sql)
    resultset_to_hash(rs)
  ensure
    stmt.close if stmt
  end

  def resultset_to_hash(resultset)
    rows = []

    while resultset.next
      rows << row_to_hash(resultset)
    end

    rows
  end

  def row_to_hash(resultset)
    column_count = resultset.meta_data.column_count
    row = {}

    (1..column_count).each do |column_index|
      name = get_column_name(resultset, column_index)
      value = get_column_value(resultset, column_index)
      row[name] = value
    end

    row
  end

  def inspect_column(resultset, column_index)
    meta = resultset.meta_data
    [
      meta.get_column_type_name(column_index),
      meta.get_column_name(column_index),
      meta.get_column_label(column_index),
      meta.get_column_class_name(column_index),
      meta.get_column_display_size(column_index),
      meta.get_column_type(column_index)
    ]
  end

  def get_column_name(resultset, column_index)
    resultset.meta_data.get_column_name(column_index)
  end

  # https://gist.github.com/rwjblue/1366047
  def get_column_value(resultset, column_index)
    meta = resultset.meta_data
    case meta.get_column_type(column_index)
    when -6, -5, 5, 4 # TINYINT, BIGINT, INTEGER
      resultset.get_int(column_index).to_i
    when 41, 91 # Date
      resultset.get_date(column_index)&.toString
    when 92 # Time
      resultset.get_time(column_index).toString
    when 93 # Timestamp
      resultset.get_timestamp(column_index)&.toString
    when 2, 3, 6 # NUMERIC, DECIMAL, FLOAT
      if meta.get_scale(column_index).zero?
        resultset.get_long(column_index).to_i
      else
        resultset.get_string(column_index).to_s.to_f
      end
    when 1, -15, -9, 12
      # CHAR, NCHAR, NVARCHAR, VARCHAR
      resultset.get_string(column_index).to_s
    when 8 # [Double, double]
      resultset.get_string(column_index).to_s
    when -7 # Logical, boolean
      resultset.get_string(column_index).to_s
    else
      p [:unknown, inspect_column(resultset, column_index)]
      resultset.get_string(column_index).to_s
    end
  end
end