Java getPassword的prepareStatement引发错误

我是eclipse的新手，我正在尝试创建一个注册界面。作为一个shell，它工作正常，即如果没有输入，它将接受输入并显示警告，但它没有连接到数据库。我现在正试图用prepareStatement将它连接到我的数据库，但我收到了一些参数设置字符串的eror。我尝试用其中一个建议修复来更改错误，即“将p1的类型更改为‘字符串’”，但没有任何更改。如何使用setString作为密码

我知道并不是每个txtField都会在查询中被请求，我想在尝试插入所有txtField之前先尝试几个txtField

“ConnectDB”连接的工作原理与我在一个单独的类中连接的一样，但它只是一个简单的prepareStatement，只包含一个insert。我做错了什么

  package project_files;
    import javax.swing.*;

import Connection.ConnectDB;

import java.awt.*;  
    import java.awt.event.*;  
    import java.sql.*;
import java.util.Arrays;  
    public class registration_test extends JFrame implements ActionListener   
    {  
        Connection con = null;
        PreparedStatement pst = null;
        JLabel l1, l2, l3, l4, l5, l6, l7, l8;  
        JTextField txtname, txtid, txtDOB, txtState, txtNum;  
        JButton btnSubmit, btn2;  
        JPasswordField p1, p2;  
        private JLabel Lname;
        private JTextField textLname;
        public registration_test()  
        {  
            setVisible(true);  
            setSize(700, 700);  
            getContentPane().setLayout(null);  
            setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);  
            setTitle("Registration Form");  
            l1 = new JLabel("Registration Form");  
            l1.setForeground(Color.blue);  
            l1.setFont(new Font("Serif", Font.BOLD, 20));  
            l2 = new JLabel("First Name:");  
            l3 = new JLabel("Email-ID:");  
            l4 = new JLabel("Create Passowrd:");  
            l5 = new JLabel("Confirm Password:");  
            l6 = new JLabel("DOB");  
            l7 = new JLabel("State:");  
            l8 = new JLabel("Phone No:");   
            txtname = new JTextField();  
            txtid = new JTextField();  
            p1 = new JPasswordField();  
            p2 = new JPasswordField();  
            txtDOB = new JTextField();  
            txtState = new JTextField();  
            txtNum = new JTextField();  
            btnSubmit = new JButton("Submit");  
            btnSubmit.addActionListener(new ActionListener() {
                public void actionPerformed(ActionEvent arg0) {
                    try {
                    PreparedStatement st = ConnectDB.prepareStatement("INSERT INTO userdatabase . users (FirstName, LastName, Email, Password, Phone Number) VALUES  ('?','?','?','?'");
                    st.setString(1, txtname.getText());
                    st.setString(2, textLname.getText());
                    st.setString(3, txtid.getText());
                    st.setString(4, p1.getPassword());
                    st.setString(5, txtNum.getText());
                    pst.executeUpdate();
                    JOptionPane.showMessageDialog(null, "REGISTER SUCCESSFULLY");


                }
                catch(Exception ex){
                    JOptionPane.showMessageDialog(null, ex);

                    }
                    JFrame frmregistration_test = new JFrame("Submit");

                    if (txtname.getText().isEmpty())
                    {
                        JOptionPane.showMessageDialog(null, "All fields must be filled in", "Login Warning", JOptionPane.WARNING_MESSAGE);
                    }
                    else if (textLname.getText().isEmpty())
                    {
                        JOptionPane.showMessageDialog(null, "All fields must be filled in", "Login Warning", JOptionPane.WARNING_MESSAGE);
                    }
                    else if (txtDOB.getText().isEmpty())
                    {
                        JOptionPane.showMessageDialog(null, "All fields must be filled in", "Login Warning", JOptionPane.WARNING_MESSAGE);
                    }
                    else if (txtNum.getText().isEmpty())
                    {
                        JOptionPane.showMessageDialog(null, "All fields must be filled in", "Login Warning", JOptionPane.WARNING_MESSAGE);
                    }
                    else if (txtState.getText().isEmpty())
                    {
                        JOptionPane.showMessageDialog(null, "All fields must be filled in", "Login Warning", JOptionPane.WARNING_MESSAGE);
                    }
                    else if (txtid.getText().isEmpty())
                    {
                        JOptionPane.showMessageDialog(null, "All fields must be filled in", "Login Warning", JOptionPane.WARNING_MESSAGE);

                    }


                    else if (p1.getPassword().length == 0 || p2.getPassword().length == 0){                 
                        JOptionPane.showMessageDialog(null, "Passwords fields can not be empty.", "Woops", JOptionPane.ERROR_MESSAGE);
                    }

                    else if (!Arrays.equals(p1.getPassword(), p2.getPassword())) {
                        JOptionPane.showMessageDialog(null, "Passwords do not match.", "Woops", JOptionPane.ERROR_MESSAGE);
                    }

                    else {    
                        JOptionPane.showMessageDialog(null, "Registered Successfully", "Login Warning", JOptionPane.WARNING_MESSAGE);
                    }







                    }});





            btn2 = new JButton("Clear");  
            btnSubmit.addActionListener(this);  
            btn2.addActionListener(this);  
            l1.setBounds(100, 30, 400, 30);  
            l2.setBounds(80, 70, 200, 30);  
            l3.setBounds(80, 361, 200, 30);  
            l4.setBounds(80, 150, 200, 30);  
            l5.setBounds(80, 190, 200, 30);  
            l6.setBounds(80, 230, 200, 30);  
            l7.setBounds(80, 270, 200, 30);  
            l8.setBounds(80, 310, 200, 30);  
            txtname.setBounds(300, 70, 200, 30);  
            txtid.setBounds(300, 361, 200, 30);  
            p1.setBounds(300, 150, 200, 30);  
            p2.setBounds(300, 190, 200, 30);  
            txtDOB.setBounds(300, 230, 200, 30);  
            txtState.setBounds(300, 270, 200, 30);  
            txtNum.setBounds(300, 310, 200, 30);  
            btnSubmit.setBounds(50, 402, 100, 30);  
            btn2.setBounds(168, 402, 100, 30);  
            getContentPane().add(l1);  
            getContentPane().add(l2);  
            getContentPane().add(txtname);  
            getContentPane().add(l3);  
            getContentPane().add(txtid);  
            getContentPane().add(l4);  
            getContentPane().add(p1);  
            getContentPane().add(l5);  
            getContentPane().add(p2);  
            getContentPane().add(l6);  
            getContentPane().add(txtDOB);  
            getContentPane().add(l7);  
            getContentPane().add(txtState);  
            getContentPane().add(l8);  
            getContentPane().add(txtNum);  
            getContentPane().add(btnSubmit);  
            getContentPane().add(btn2);  

            Lname = new JLabel("Last Name");
            Lname.setBounds(80, 112, 70, 14);
            getContentPane().add(Lname);

            textLname = new JTextField();
            textLname.setBounds(300, 111, 200, 28);
            getContentPane().add(textLname);
            textLname.setColumns(10);
        }  





        public static void main(String args[])  
        {  
            new registration_test();  

        }






        public void actionPerformed(ActionEvent arg0) {
            // TODO Auto-generated method stub

        }  
    }  

如果您需要查看连接，它是：

package Connection;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.SQLException;

public class ConnectDB {
    //DB Connection variables

    static Connection connection = null;
    static String databaseName = "";
    static String url = "jdbc:mysql://localhost:3306/" +databaseName;

    static String username = "root";
    static String password = "pass1234";

    public static void main(String[] args) throws InstantiationException, IllegalAccessException, ClassNotFoundException, SQLException {
        connection = DriverManager.getConnection(url, username, password);

        PreparedStatement ps = connection.prepareStatement("INSERT INTO `userdatabase` . `user` (`UserId`, `FirstName`, `LastName`, `Phone Number`, `Email`, `Password`) VALUES ('5', 'Eugene', 'Miller', '586231234', 'Eugene1@gmail.com', 'password');");

        int status = ps.executeUpdate();


        if (status != 0) {
            System.out.println("Datebase was Connected");
            System.out.println("Record was Inserted");




        }
    }

    public static PreparedStatement prepareStatement(String string) {
        // TODO Auto-generated method stub
        return null;
    }

}

---

到目前为止，我发现了一些错误：

• 方法

  ConnectDb.prepareStatement

  应该返回一个非空的、有效的PreparedStatement对象（正如@Abra明智地指出的那样）。实现它时，请记住正确初始化

  连接

  对象
• 查看方法

  prepareStatement

  中设置的SQL语句：必须在VALUES子句中放置与

  INSERT

  子句中的列一样多的占位符（问号），并且必须不带引号。此外，请记住，一列的名称不应包含任何空格

---

你的问题，并发布你得到的错误消息和堆栈跟踪。方法返回

char[]

，它不是

字符串

。在你发布的代码中，class

ConnectDB

中的方法

prepareStatement（String）

返回空值。它不应该返回一个实际的

PreparedStatement

对象吗？