Ruby on rails 未定义的方法'；执行查询'；零级：零级

我想连接到数据库并使用JRuby执行一个非常简单的查询。它正在建立连接，但无法执行查询。代码如下：

  require 'oracle_connection'

 #Edit these for your database schema

class OracleConnectionDriver

   def initialize(user, pwd, url)
      print "Run at #{Time.now} using JRuby #{RUBY_VERSION}\n\n"user
      @conn = OracleConnection.new(user, pwd, url)
      puts #@conn, "\n"
   end

  def is_user?(user_name)
    puts "Checking if user exists: "
      select_sql = <<-EOF
        SELECT COUNT(*)
        FROM users
        WHERE username = upper('#{user_name})
        EOF

    select_stmt = #@conn.create_statement
    reselt_set = select_stmt.execute_query(select_sql)
     while(result_set.next)
        puts " Resultset [#{result_set.getInt(1)}]"
     end
   end


  print "\nEnded at #{Time.now}\n"

end

test_connection =  OracleConnectionDriver.new('USERNAME', 'PWD', 'jdbc:oracle:thin:@XXXXX:8888/YYYY')
test_connection.is_user?('ABC')

---

有人能帮我修一下吗？谢谢

看起来您在这一行有问题：

选择_stmt=#@conn.create_语句

#字符已注释掉赋值，因此select_stmt变量未初始化

select_stmt = #@conn.create_statement

这是右边的评论。那么在下一行：

reselt_set = select_stmt.execute_query(select_sql)

---

select_stmt为零…因此出现错误消息。

我去掉了“#”，现在它正在工作。谢谢你指出这一点。这解决了问题。非常感谢。

reselt_set = select_stmt.execute_query(select_sql)