正确的方法从数据库返回数据

Question

我是Java新手，在从数据库访问数据时遇到困难。我正在使用SQL服务器，WebDriver和Java。我创建了一个类来连接数据库并将数据返回给调用者。我能够在二维数组ex- Object [] []数据集中从数据库中检索数据。

调用者类将获得类似于 - Object [] []数据集的数据。有时我的数据值为0.00（这是运费）。

我在调用者程序中检查此值时遇到困难，因为我想检查运费是否为0。

我尝试了以下方式，但我不确定这是否是正确的方法。有人可以告诉我正确的方法吗？

private DecimalFormat freight= new DecimalFormat("#.##");


dbObj = new DBOperations();
dbObj.establishConnection("DSN_dbtest");
dbObj.executeQuery(queryFS);
resultSet= dbObj.getDataResult();

freightCharge =  resultSet[0][3].toString();

System.out.println("Freight charge=" + freightCharge); =>Displays .0000

if( freight.format(Double.parseDouble(freightCharge.toString())).equalsIgnoreCase("0"))
            System.out.println("Freight charge is =" +freight.format(Double.parseDouble(freightCharge.toString())) );

类 - DBOperations -

package lampsplus.utilities;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.ResultSetMetaData;
import java.sql.Statement;
import java.sql.Types;

public class DBOperations {

    private String connectionString=null, formattedString;
    private Connection  conn;
    private Statement stmt;
    private ResultSet resSet;
    private ResultSetMetaData rsMD;
    private Object[][] dataSet;
    int rows,cols;





    /**
     * This method returns a result set retrieved from the database.
     *
     * @return Object  - two dimensional array of fetched data. 
     */ 
    public Object[][] getDataResult()
    {
        return dataSet;
    }







    /**
     * Class constructor to initialize variables.
     *
     */ 
     public DBOperations()
     {
         System.out.println("initializing constructor dboperations:");
         connectionString="jdbc:odbc:";
         this.conn = null;
         this.stmt = null;
         this.resSet = null;
         this.dataSet=null;
     }


    /**
     * This method is used to create a database connection.
     *
     * @param string - dsn name to connect the db
     * @return void
     * @throws Exception - An unexpected exception
     */ 
     public void establishConnection(String dsnName) throws Exception
     {
         System.out.println("Establishing connection:");

         Class.forName("sun.jdbc.odbc.JdbcOdbcDriver");
         connectionString= connectionString+dsnName;
         System.out.println("connection string :" + connectionString);
         conn = DriverManager.getConnection(connectionString);
         stmt=conn.createStatement(ResultSet.TYPE_SCROLL_INSENSITIVE, ResultSet.CONCUR_READ_ONLY);
     }


     /**
      * This method is used to execute a database query.
      *
      * @param string - Query to execute
      * @throws Exception - An unexpected exception
      */    
     public void executeQuery(String query) throws Exception
     {

         resSet = stmt.executeQuery(query);
         rsMD= resSet.getMetaData();

         rows=cols=0;
         while(resSet.next())
             rows++;

         cols=rsMD.getColumnCount();
         dataSet= new Object[rows][cols];


         rows=0;
         resSet.beforeFirst();
         System.out.println("Data type ====" + resSet.getClass().getName());
         while(resSet.next())
         {   
              for(cols=0;cols<rsMD.getColumnCount(); cols++)
              {
                  if (rsMD.getColumnType(cols+1) == Types.NVARCHAR    )
                      dataSet[rows][cols]= resSet.getString(cols+1).toString();

                  else
                      dataSet[rows][cols] =(Object)resSet.getString(cols+1);


                  System.out.print(" " + dataSet[rows][cols]);
              }
              rows++;
         }   
     }


     /**
      * This method is used to close a database connection.
      *
      * @return void
      * @throws Exception - An unexpected exception
      */    
     public void closeConnection() throws Exception
     {
         System.out.println("closing connection:");
          connectionString=null;
          resSet.close();
          stmt.close();
          conn.close();
     }

}