Java 更新查询不起作用

Question

我有数据访问对象工厂类。有两种方法：一种是检索数据，一种是更新表。检索数据的方法正常工作。但是更新方法不起作用。我无法弄清楚问题所在。请帮忙。

这是工厂类：

public class ChequeDAOImpl implements ChequeDAO {

public DBConnect dbConnection;

@Override
public List<Cheque> getCheques() throws SQLException{

    List<Cheque> cheques = new ArrayList<Cheque>();
    Connection connection = dbConnection.getConnection();

    try{
        Statement statement = connection.createStatement();
        ResultSet result = statement.executeQuery("select * from TblProj");


        while(result.next()) {
            Cheque cheque = new Cheque();   
            cheque.setName(result.getString("Name"));
            cheque.setAmount(result.getDouble("Amount"));
            cheque.setDate(result.getDate("Date"));
            cheque.setChqNum(result.getString("CNumber"));
            cheque.setValue(result.getDouble("Value"));

            cheques.add(cheque);                            
        } 
    }catch(Exception exception){
        exception.printStackTrace();
    }finally{
        connection.close();
    }       

    return cheques;
}

@Override
    public void updateFlag(String chNum) throws SQLException{
         DBConnect Connection = null;
        Connection conn = Connection.getConnection();

        try{                                        


            PreparedStatement stmt = (PreparedStatement) conn.prepareStatement("UPDATE TblProj SET flag = ? WHERE CNumber = ? ");
            int i= stmt.executeUpdate();
            stmt.setString(1, "1");
            stmt.setString(2, chNum);
            if(i>0)
            {
                JOptionPane.showMessageDialog(null, "Updated successfully");

            }



        }

        catch(Exception ex){

           JOptionPane.showMessageDialog(null, ex.toString());
        }
        finally{

            conn.close();
        }
    }


public DBConnect getConnection() {
    return dbConnection;
}

public void setConnection(DBConnect connection) {
    this.dbConnection = connection;
}

}

这就是我使用 updateFlag 方法的方式：

dao.updateFlag(gui.chqNo);

Answer 1

请重写你的prepared statement如下，首先设置prepared statement的参数，然后使用executeUpdate()方法执行。

PreparedStatement stmt = (PreparedStatement) conn.prepareStatement("UPDATE TblProj SET flag = ? WHERE CNumber = ?");

        stmt.setInt(1, 1);
        stmt.setString(2, chNum);
        int i= stmt.executeUpdate();