找不到方法prepareStatement(query) | 找不到符号

Question

The error reads Cannot find Symbol

You can see the connection to the class

I keep getting the error that when I use getconnection.prepareStatement(query) I can't even find it in autocomplete, it doesn't even exist. I've also tried My_CNX.getConnection().prepareStatement(query);

The Code for my connection class

package login_register_design;

import com.mysql.cj.jdbc.MysqlDataSource;
import com.sun.jdi.connect.spi.Connection;
import java.sql.PreparedStatement;
import java.sql.SQLException;
import java.util.logging.Level;
import java.util.logging.Logger;

/**
 *
 * @author narai
 */
public class My_CNX {
      private static String servername = "localhost";
    private static String username = "root";
    private static String dbname  = "users_db";
    private static Integer portnumber  = 3306;
    private static String password = "";
  
    
    public static Connection getConnection()
    {
         
        Connection cnx = null;
        
        MysqlDataSource datasource = new MysqlDataSource();
        
        datasource.setServerName(servername);
        datasource.setUser(username);
        datasource.setPassword(password);
        datasource.setDatabaseName(dbname);
        datasource.setPortNumber(portnumber);
        
        
          try {
              cnx = (Connection) datasource.getConnection();
         
          } catch (SQLException ex) {
              Logger.getLogger(" Get Connection -> " + My_CNX.class.getName()).log(Level.SEVERE, null, ex);
          }
        
        
        return cnx;
    }

    /**
     *
     * @param query
     * @return
     */
    public static PreparedStatement prepareStatement(String query) {
        throw new UnsupportedOperationException("Not supported yet."); //To change body of generated methods, choose Tools | Templates.
    }
}

The code for my JformButton!

private void jButton_LoginActionPerformed(java.awt.event.ActionEvent evt) {                                              
        
            //  PreparedStatement st;
            ResultSet rs;
            
            // get the username & password
            String username = jTextField_Username.getText();
            String password = String.valueOf(jPasswordField.getPassword());
            
            //  System.out.println("The password is " + password);
            
            //create a select query to check if the username and the password exist in the database
            String query = "SELECT * FROM `users' WHERE `Email` = ? AND `Password` = ?";
            //  System.out.println(My_CNX.getConnection());
            //  st = My_CNX.getConnection();
            Connection cnx = null;
            PreparedStatement cnx1;
            // st = (PreparedStatement) My_CNX.getConnection();
            PreparedStatement st;
            
            try {
            
            st= My_CNX.getConnection().prepareStatement(query);
            st.setString(1, username);
            st.setString(2, password);
            rs = st.executeQuery();
            
            if(rs.next())
            {
                // show a new form
                Dashboard form = new Dashboard();
                form.setVisible(true);
                form.pack();
                form.setLocationRelativeTo(null);
                // close the current form(login form)
                this.dispose();
                
            }else{
                // error message
                JOptionPane.showMessageDialog(null, "Invalid Username / Password","Login Error",2);
            }
        }
    catch (SQLException ex) {
            java.util.logging.Logger.getLogger(Login_Form.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        }
                                               
    }  

My Imports for the Button class

import com.sun.jdi.connect.spi.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import javax.swing.JFrame;
import javax.swing.JOptionPane;
import java.io.IOException;                              

After some help, I've managed to solve the error.. But now when I click on the button I'm getting this error thrown at me!

Holy. There's no error now! Thank you so much! I'm still getting an error when I click the login button tho.

May 26, 2021 3:52:02 PM login_register_design.Login_Form jButton_LoginActionPerformed
SEVERE: null
java.sql.SQLException: Parameter index out of range (1 > number of parameters, which is 0).
    at com.mysql.cj.jdbc.exceptions.SQLError.createSQLException(SQLError.java:129)
    at com.mysql.cj.jdbc.exceptions.SQLError.createSQLException(SQLError.java:97)
    at com.mysql.cj.jdbc.exceptions.SQLError.createSQLException(SQLError.java:89)
    at com.mysql.cj.jdbc.exceptions.SQLError.createSQLException(SQLError.java:63)
    at com.mysql.cj.jdbc.ClientPreparedStatement.checkBounds(ClientPreparedStatement.java:1373)
    at com.mysql.cj.jdbc.ClientPreparedStatement.getCoreParameterIndex(ClientPreparedStatement.java:1386)
    at com.mysql.cj.jdbc.ClientPreparedStatement.setString(ClientPreparedStatement.java:1753)
    at login_register_design.Login_Form.jButton_LoginActionPerformed(Login_Form.java:253)
    at login_register_design.Login_Form$6.actionPerformed(Login_Form.java:131)
    at java.desktop/javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:1972)
    at java.desktop/javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2313)
    at java.desktop/javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:405)
    at java.desktop/javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:262)
    at java.desktop/javax.swing.plaf.basic.BasicButtonListener.mouseReleased(BasicButtonListener.java:279)
    at java.desktop/java.awt.AWTEventMulticaster.mouseReleased(AWTEventMulticaster.java:297)
    at java.desktop/java.awt.Component.processMouseEvent(Component.java:6617)
    at java.desktop/javax.swing.JComponent.processMouseEvent(JComponent.java:3342)
    at java.desktop/java.awt.Component.processEvent(Component.java:6382)
    at java.desktop/java.awt.Container.processEvent(Container.java:2264)
    at java.desktop/java.awt.Component.dispatchEventImpl(Component.java:4993)
    at java.desktop/java.awt.Container.dispatchEventImpl(Container.java:2322)
    at java.desktop/java.awt.Component.dispatchEvent(Component.java:4825)
    at java.desktop/java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4934)
    at java.desktop/java.awt.LightweightDispatcher.processMouseEvent(Container.java:4563)
    at java.desktop/java.awt.LightweightDispatcher.dispatchEvent(Container.java:4504)
    at java.desktop/java.awt.Container.dispatchEventImpl(Container.java:2308)
    at java.desktop/java.awt.Window.dispatchEventImpl(Window.java:2773)
    at java.desktop/java.awt.Component.dispatchEvent(Component.java:4825)
    at java.desktop/java.awt.EventQueue.dispatchEventImpl(EventQueue.java:772)
    at java.desktop/java.awt.EventQueue$4.run(EventQueue.java:721)
    at java.desktop/java.awt.EventQueue$4.run(EventQueue.java:715)
    at java.base/java.security.AccessController.doPrivileged(AccessController.java:391)
    at java.base/java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:85)
    at java.base/java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:95)
    at java.desktop/java.awt.EventQueue$5.run(EventQueue.java:745)
    at java.desktop/java.awt.EventQueue$5.run(EventQueue.java:743)
    at java.base/java.security.AccessController.doPrivileged(AccessController.java:391)
    at java.base/java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:85)
    at java.desktop/java.awt.EventQueue.dispatchEvent(EventQueue.java:742)
    at java.desktop/java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:203)
    at java.desktop/java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:124)
    at java.desktop/java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:113)
    at java.desktop/java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:109)
    at java.desktop/java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:101)
    at java.desktop/java.awt.EventDispatchThread.run(EventDispatchThread.java:90)

Answer 1

You're importing: com.sun.jdi.connect.spi.Connection;

It should be: java.sql.Connection