database-schema - com.mysql.jdbc.exceptions.jdbc4.MySQLSyntaxErrorException：未知数据库'dbname'

Question

尝试通过java连接到mysql数据库时出现以下错误

com.mysql.jdbc.exceptions.jdbc4.MySQLSyntaxErrorException：未知数据库'dbname'

我在数据库位于本地主机上时编写了相同的代码并且它可以工作，但是在删除以前的连接并在新连接中创建新表后会出现错误。我已经dbname在新服务器实例的新连接中创建了 mysql 中的数据库，请告诉我如何从 mysql 获取 db 域以及如何解决此问题，我的代码如下：

public static void main(String[] args) throws ClassNotFoundException, SQLException, FileNotFoundException 
{

    try
    {

        int i;
        int numcol = 1;
        int j;
        int count = 0;
        int c = 0;
        Class.forName("com.mysql.jdbc.Driver");
        Connection con=null;
        con=DriverManager.getConnection("jdbc:mysql://localhost:3306/dbname","root", "ellimist");
        Statement st=(Statement) con.createStatement();
        FileInputStream file = new FileInputStream(new File("C:\\Users\\krayak\\Desktop\\Final.xlsx"));
        XSSFWorkbook workbook=new XSSFWorkbook(file);
        XSSFSheet sheet=workbook.getSheetAt(0);
        List sheetdata=new ArrayList();
        List a=new ArrayList();
        int numrow=sheet.getPhysicalNumberOfRows();
        Iterator<Row> rowiterator=sheet.rowIterator();
        while(rowiterator.hasNext())
        {
            Row row =rowiterator.next();
            List data=new ArrayList();
            for(i=0;i<numcol;i++)
            {
                XSSFCell cell;
                if(row.getCell(i)==null)
                {
                    cell=(XSSFCell) row.createCell(i);
                    data.add(cell);
                }
                else
                {
                    cell=(XSSFCell) row.getCell(i);
                    data.add(cell);
                }
            }
            sheetdata.add(data);
        }
        file.close();
        for(i=numrow;i<sheetdata.size();i++)
        {
            List list=(List) sheetdata.get(i);
            for(j=0;j<numcol;j++)
            {
                XSSFCell cell=(XSSFCell) list.get(j);
                if (cell.getCellType() == Cell.CELL_TYPE_NUMERIC)
               {
                   a.add(cell.getNumericCellValue());
                   System.out.println(cell.getNumericCellValue());
               }
               else if (cell.getCellType() == Cell.CELL_TYPE_STRING)
               {
                   a.add(cell.getRichStringCellValue());
                   System.out.println(cell.getRichStringCellValue());
               }
               else if (cell.getCellType() == Cell.CELL_TYPE_BOOLEAN)
               {
                   a.add(cell.getBooleanCellValue());
                   System.out.println(cell.getBooleanCellValue());
               }
               else if (cell.getCellType() == Cell.CELL_TYPE_BLANK)
               {
                   a.add(null);
                   System.out.println(cell);
               }
            }
            count++;
        }
        for(i=0;i<count;i++)
        {
            String sql="insert into testing.test (name) values ('";
            sql += a.get(c++) + "')";
            st.executeUpdate(sql); 
        }
    }
    catch(NullPointerException e)
    {
        System.out.println("null pointer exception"+e);
        e.printStackTrace();
    }
    catch(SQLException ex)
    {
        System.out.println("sqlexception "+ex);
    }
    catch(FileNotFoundException ex)
    {
        System.out.println("file not found "+ ex);
    }
    catch(Exception ex)
    {
        System.out.println("exception\n"+ex);
    }
}

}