Java ID 验证错误：连接器错误

Question

我尝试检查标识符是否存在，但出现线路错误

st = Connecter.getConnection().prepareStatement(query)

出现错误：找不到符号 符号：方法prepareStatement(String) 位置：类对象

并在行中

catch (SQLException ex) {
            Logger.getLogger(Login_Form.class.getName()).log(Level.SEVERE, null, ex);

出现错误找不到符号 符号：类 SQLException 位置：类Login_Form

这是我的全部代码

PreparedStatement st;
        ResultSet rs;

        // donnez l'username et le password 
        String username = jTextField_Username.getText();
        String password = String.valueOf(jPasswordField.getPassword());

        // requete indiquant si les identifiants existent 
        String query = "SELECT * FROM 'users' WHERE 'username' = ? AND 'password' = ?";

        try {
            st = Connecter.getConnection().prepareStatement(query)

            st.setString(1, username);
            st.setString(2, password);
            rs = st.executeQuery();

            if(rs.next())

            {
                // Show my new form 
            }else{
                // Error message 
            }


        } catch (SQLException ex) {
            Logger.getLogger(Login_Form.class.getName()).log(Level.SEVERE, null, ex);
        }

我的连接器页面：

package javaapplicationhotel2;

/*
 * To change this license header, choose License Headers in Project Properties.
 * To change this template file, choose Tools | Templates
 * and open the template in the editor.
 */
import java.sql.*;

/**
 *
 * @author camil
 */




public class Connecter {

    static Object getConnection() {
        throw new UnsupportedOperationException("Not supported yet."); //To change body of generated methods, choose Tools | Templates.
    }
    Connection con; 



    public Connecter() {
      try{
      Class.forName("com.mysql.cj.jdbc.Driver");
      }catch(ClassNotFoundException e){
          System.err.println(e);


    }
    try{
    con=DriverManager.getConnection("jdbc:mysql://localhost:3306/hotel","root","");
    }catch(SQLException e){System.err.println(e);}
    }
    Connection obtenirconnexion(){return con;}

    PreparedStatement prepareStatement(String select__from_classe) {
        throw new UnsupportedOperationException("Not supported yet."); //To change body of generated methods, choose Tools | Templates.



    }


}

你有解决办法吗？

Answer 1

问题：

Connecter::getConnection 没有返回 Connection 对象。

解决方案：

替换

static Object getConnection() {
    throw new UnsupportedOperationException("Not supported yet."); // To change body of generated methods, choose Tools | Templates.
}
Connection con; 

与

public static Connection getConnection() {
    return con;
}
static Connection con;