Java将excel文件（POI）导入mysql关于空白列

Question

I tried to import excel file into database(MySQL).

When Excel has empty column, Console window shows error message

... Import rows 16 Import rows 17 Import rows 18 Import rows 19 Import rows 20 Import rows 21 Import rows 22 Import rows 23 Exception in thread "main" java.lang.NullPointerException at jdbcTest.main(jdbcTest.java:68)

How to fix this error?. My source code is

public static void main(String[] args) {
    // TODO Auto-generated method stub
    String url    =   "jdbc:mysql://localhost/dahan?characterEncoding=utf8";
    String user    =   "root";
    String password   =   "apmsetup";

    try{
        Class.forName("com.mysql.jdbc.Driver");  
        Connection con = (Connection) DriverManager.getConnection(url,user,password);  
        con.setAutoCommit(false);  
        PreparedStatement pstm1 = null ; 
        FileInputStream input = new FileInputStream("C:/Users/hyunwoo/Downloads/Personal Contacts.xls");  
        POIFSFileSystem fs = new POIFSFileSystem( input );  
        @SuppressWarnings("resource")
        HSSFWorkbook wb = new HSSFWorkbook(fs);  
        HSSFSheet sheet = wb.getSheetAt(0); 
        Row row;
        String del = "DROP TABLE IF EXISTS `dahanMail`";
        /*String cre = "CREATE TABLE `dahanMail` (`Fullname`  varchar(50),`Firstname`  varchar(50),`Lastname`  varchar(50) ,`Nickname`  varchar(50),"
                + "`Company`  varchar(500),`Department`  varchar(500),`Position`  varchar(500),`Mail1`  varchar(50),"
                + "`Mail2`  varchar(50),`Number1`  varchar(50),`Number2`  varchar(50),`Number3`  varchar(50),"
                + "`PhoneNumber1`  varchar(50),`PhoneNumber2`  varchar(50),`Fax1`  varchar(50),`Fax2`  varchar(50),"
                + "`Address`  varchar(50),`Website`  varchar(50),`id`  int NOT NULL ,PRIMARY KEY (`id`))ENGINE=InnoDB DEFAULT CHARSET=utf8;";*/
        pstm1 = (PreparedStatement) con.prepareStatement(del);
        pstm1.execute();
        del = "CREATE TABLE `dahanMail` (`Fullname`  varchar(50) ,`Firstname`  varchar(50),`Lastname`  varchar(50) ,"
                + "`id`  int NOT NULL ,PRIMARY KEY (`id`))ENGINE=InnoDB DEFAULT CHARSET=utf8;";
        pstm1 = (PreparedStatement) con.prepareStatement(del);
        pstm1.execute();

        //String sql = "INSERT INTO dahanmail VALUES(?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?)";
        String sql = "INSERT INTO dahanmail VALUES(?,?,?,?)";
        PreparedStatement pstm = (PreparedStatement) con.prepareStatement(sql);


        for(int i = sheet.getFirstRowNum(); i<=sheet.getLastRowNum(); i++){
            row = sheet.getRow(i);

                   pstm.setString(1, row.getCell(0).getStringCellValue());
                   pstm.setString(2,row.getCell(1).getStringCellValue());
                   pstm.setString(3,row.getCell(2).getStringCellValue());
                /* pstm.setString(4,row.getCell(3).getStringCellValue());
                   pstm.setString(5,row.getCell(4).getStringCellValue());
                   pstm.setString(6,row.getCell(5).getStringCellValue());
                   pstm.setString(7,row.getCell(6).getStringCellValue());
                   pstm.setString(8,row.getCell(7).getStringCellValue());
                   pstm.setString(9,row.getCell(8).getStringCellValue());
                   pstm.setString(10,row.getCell(9).getStringCellValue());
                   pstm.setString(11,row.getCell(10).getStringCellValue());
                   pstm.setString(12,row.getCell(11).getStringCellValue());
                   pstm.setString(13,row.getCell(12).getStringCellValue());
                   pstm.setString(14,row.getCell(13).getStringCellValue());
                   pstm.setString(15,row.getCell(14).getStringCellValue());
                   pstm.setString(16,row.getCell(15).getStringCellValue());
                   pstm.setString(17,row.getCell(16).getStringCellValue());
                   pstm.setString(18,row.getCell(17).getStringCellValue());*/
                   pstm.setInt(4,(int)row.getCell(18).getNumericCellValue());
                   pstm.execute();
                   pstm.clearParameters();
                   System.out.println("Import rows "+i);
               // Do something useful with the cell's contents

        }
        con.commit();
        pstm.close();
        con.close();
        input.close();
        System.out.println("Success import excel to mysql table");
    }catch(ClassNotFoundException e){
        System.out.println(e);
    }catch(SQLException ex){
        System.out.println(ex);
    }catch(IOException ioe){
        System.out.println(ioe);
    }
}
}

Answer 1

It is well-known (and documented in multiple other answers), that POI's get cell method will return null on empty cells.

Your code then calls getStringCellValue on the null, which causes the Exception.