java.sql.PreparedStatement无法转换为com.mysql.jdbc.PreparedStatement。

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英文:

java.sql.PreparedStatement cannot be converted to com.mysql.jdbc.PreparedStatement

问题

package demo;

import java.awt.HeadlessException;
import java.sql.Statement;
import java.sql.Connection; // Import the correct Connection class
import java.sql.PreparedStatement; // Import the correct PreparedStatement class
import java.sql.DriverManager;
import java.sql.ResultSet;
import javax.swing.JOptionPane;
import java.sql.SQLException; 

public class NewJFrame extends javax.swing.JFrame {

    Connection con;
    PreparedStatement pst;
    ResultSet rs;

    public NewJFrame() {
        initComponents();
    }

    // ... (Rest of the code remains the same)

    private void jButton1ActionPerformed(java.awt.event.ActionEvent evt) {  
        String uname=jTextField1.getText();
        String pword=jPasswordField1.getText();
        String option=jComboBox1.getSelectedItem().toString();
        if(uname.equals("")||pword.equals("")||option.equals("")){
            JOptionPane.showMessageDialog(rootPane,"Some fields are Empty!!","Error",1);}
        else{
            try{
                con=DriverManager.getConnection("jdbc:mysql://your_database_url_here", "username", "password"); // Provide your database URL, username, and password
                pst=con.prepareStatement("select * from `login` where username=? and password=?"); // Corrected typo 'passwor' to 'password'
                pst.setString(1, uname); // Corrected typo 'unmae' to 'uname'
                pst.setString(2, pword);
                rs=pst.executeQuery();
                if(rs.next()){
                    String s1=rs.getString("option");
                    if(option.equalsIgnoreCase("Admin")&&s1.equalsIgnoreCase("admin"))
                    {
                        AdminPage ad=new AdminPage(uname);
                        ad.setVisible(true);
                        setVisible(false);
                    }
                    if(option.equalsIgnoreCase("User")&&s1.equalsIgnoreCase("user")) // Corrected 'admin' to 'user'
                    {
                        UserPage ad=new UserPage(uname);
                        ad.setVisible(true);
                        setVisible(false);
                    }
                }
                else{
                    JOptionPane.showMessageDialog(rootPane, "Username or password not matched","Login Error", 1);
                }
                    
            }
            catch(Exception ex){ // Corrected 'Excepton' to 'Exception'
                System.out.println(""+ex);}
        }
    }

    // ... (Rest of the code remains the same)
}

Please note:

  1. You need to replace "jdbc:mysql://your_database_url_here", "username", "password" with your actual database URL, username, and password.
  2. I've corrected the typos in the code, like the misspelled variable names, and replaced Connections.getConnection() with DriverManager.getConnection(). Also, I've corrected the usage of "option" as "user" instead of "admin" when checking for the user role.
  3. If you are still encountering errors after these corrections, ensure that your database connection details are accurate and that you have the MySQL JDBC driver in your project's classpath.
英文:

I was trying to make a GUI application using mysql database connection which is getting error.
Here is my code.

package demo;
import java.awt.HeadlessException;
import java.sql.Statement;
import com.mysql.jdbc.Connection;
import com.mysql.jdbc.PreparedStatement;
import java.sql.DriverManager;
import java.sql.ResultSet;
import javax.swing.JOptionPane;
import java.sql.SQLException; 
public class NewJFrame extends javax.swing.JFrame {
Connection con;
PreparedStatement pst;
ResultSet rs;
public NewJFrame() {
initComponents();
}
@SuppressWarnings("unchecked")                         
private void initComponents() {
jPanel1 = new javax.swing.JPanel();
jLabel1 = new javax.swing.JLabel();
jLabel2 = new javax.swing.JLabel();
jLabel3 = new javax.swing.JLabel();
jLabel4 = new javax.swing.JLabel();
jTextField1 = new javax.swing.JTextField();
jComboBox1 = new javax.swing.JComboBox<>();
jButton1 = new javax.swing.JButton();
jButton2 = new javax.swing.JButton();
jPasswordField1 = new javax.swing.JPasswordField();
setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);
jLabel1.setBackground(new java.awt.Color(51, 204, 0));
jLabel1.setFont(new java.awt.Font("Times New Roman", 2, 24)); // NOI18N
jLabel1.setHorizontalAlignment(javax.swing.SwingConstants.CENTER);
jLabel1.setText("LOGIN PAGE");
jLabel2.setFont(new java.awt.Font("Trebuchet MS", 1, 14)); // NOI18N
jLabel2.setText("Username");
jLabel3.setFont(new java.awt.Font("Trebuchet MS", 1, 14)); // NOI18N
jLabel3.setText("Password");
jLabel4.setFont(new java.awt.Font("Trebuchet MS", 1, 14)); // NOI18N
jLabel4.setText("Select User");
jComboBox1.setModel(new javax.swing.DefaultComboBoxModel<>(new String[] { "Select", "Admin", "User" }));
jButton1.setFont(new java.awt.Font("Times New Roman", 1, 18)); // NOI18N
jButton1.setText("LOGIN");
jButton1.addActionListener(new java.awt.event.ActionListener() {
public void actionPerformed(java.awt.event.ActionEvent evt) {
jButton1ActionPerformed(evt);
}
});
jButton2.setFont(new java.awt.Font("Times New Roman", 1, 18)); // NOI18N
jButton2.setText("CANCEL");
jButton2.addActionListener(new java.awt.event.ActionListener() {
public void actionPerformed(java.awt.event.ActionEvent evt) {
jButton2ActionPerformed(evt);
}
});
javax.swing.GroupLayout jPanel1Layout = new javax.swing.GroupLayout(jPanel1);
jPanel1.setLayout(jPanel1Layout);
jPanel1Layout.setHorizontalGroup(
jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGroup(jPanel1Layout.createSequentialGroup()
.addContainerGap()
.addComponent(jLabel1, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
.addContainerGap())
.addGroup(jPanel1Layout.createSequentialGroup()
.addGap(54, 54, 54)
.addGroup(jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING, false)
.addComponent(jLabel3, javax.swing.GroupLayout.DEFAULT_SIZE, 174, Short.MAX_VALUE)
.addComponent(jLabel2, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
.addComponent(jLabel4, javax.swing.GroupLayout.DEFAULT_SIZE, 174, Short.MAX_VALUE)
.addComponent(jButton1, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE))
.addGap(70, 70, 70)
.addGroup(jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING, false)
.addComponent(jTextField1)
.addComponent(jComboBox1, 0, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
.addComponent(jButton2, javax.swing.GroupLayout.DEFAULT_SIZE, 180, Short.MAX_VALUE)
.addComponent(jPasswordField1))
.addContainerGap(149, Short.MAX_VALUE))
);
jPanel1Layout.setVerticalGroup(
jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGroup(jPanel1Layout.createSequentialGroup()
.addComponent(jLabel1, javax.swing.GroupLayout.PREFERRED_SIZE, 66, javax.swing.GroupLayout.PREFERRED_SIZE)
.addGap(42, 42, 42)
.addGroup(jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addComponent(jLabel2, javax.swing.GroupLayout.PREFERRED_SIZE, 30, javax.swing.GroupLayout.PREFERRED_SIZE)
.addGroup(jPanel1Layout.createSequentialGroup()
.addGap(6, 6, 6)
.addComponent(jTextField1, javax.swing.GroupLayout.PREFERRED_SIZE, 36, javax.swing.GroupLayout.PREFERRED_SIZE)))
.addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
.addGroup(jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
.addComponent(jLabel3, javax.swing.GroupLayout.PREFERRED_SIZE, 30, javax.swing.GroupLayout.PREFERRED_SIZE)
.addComponent(jPasswordField1, javax.swing.GroupLayout.PREFERRED_SIZE, 38, javax.swing.GroupLayout.PREFERRED_SIZE))
.addGap(24, 24, 24)
.addGroup(jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING, false)
.addComponent(jLabel4, javax.swing.GroupLayout.DEFAULT_SIZE, 30, Short.MAX_VALUE)
.addComponent(jComboBox1))
.addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED, 31, Short.MAX_VALUE)
.addGroup(jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
.addComponent(jButton1, javax.swing.GroupLayout.PREFERRED_SIZE, 47, javax.swing.GroupLayout.PREFERRED_SIZE)
.addComponent(jButton2, javax.swing.GroupLayout.PREFERRED_SIZE, 47, javax.swing.GroupLayout.PREFERRED_SIZE))
.addGap(29, 29, 29))
);
javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane());
getContentPane().setLayout(layout);
layout.setHorizontalGroup(
layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addComponent(jPanel1, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
);
layout.setVerticalGroup(
layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addComponent(jPanel1, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
);
pack();                  
private void jButton2ActionPerformed(java.awt.event.ActionEvent evt) {                                         
System.exit(0);
}                                        
private void jButton1ActionPerformed(java.awt.event.ActionEvent evt) {  
String uname=jTextField1.getText();
String pword=jPasswordField1.getText();
String option=jComboBox1.getSelectedItem().toString();
if(uname.equals("")||pword.equals("")||option.equals("")){
JOptionPane.showMessageDialog(rootPane,"Some fiels are Empty!!","Error",1);}
else{
try{
con=Connections.getConnection();
pst=con.prepareStatement("select * from `login` where username=? and passwor=?");
pst.setString(1, unmae);
pst.setString(2, pword);
rs=pst.executeQuery();
if(rs.next()){
String s1=rs.getString("option");
if(option.equalsIgnoreCase("Admin")&&s1.equalsIgnoreCase("admin"))
{
AdminPage ad=new AdminPage(uname);
ad.setVisible(true);
setVisible(false);
}
if(option.equalsIgnoreCase("User")&&s1.equalsIgnoreCase("admin"))
{
UserPage ad=new UserPage(uname);
ad.setVisible(true);
setVisible(false);
}
}
else{
JOptionPane.showMessageDialog(rootPane, "Username orr passswoord not mached","Login Error", 1);
}
}
catch(Excepton ex){
System.out.println(""+ex);}
}
}                                        
public static void main(String args[]) {
try {
for (javax.swing.UIManager.LookAndFeelInfo info : javax.swing.UIManager.getInstalledLookAndFeels()) {
if ("Nimbus".equals(info.getName())) {
javax.swing.UIManager.setLookAndFeel(info.getClassName());
break;
}
}
} catch (ClassNotFoundException ex) {
java.util.logging.Logger.getLogger(NewJFrame.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
} catch (InstantiationException ex) {
java.util.logging.Logger.getLogger(NewJFrame.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
} catch (IllegalAccessException ex) {
java.util.logging.Logger.getLogger(NewJFrame.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
} catch (javax.swing.UnsupportedLookAndFeelException ex) {
java.util.logging.Logger.getLogger(NewJFrame.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
}
java.awt.EventQueue.invokeLater(new Runnable() {
public void run() {
new NewJFrame().setVisible(true);
}
});
}
private javax.swing.JButton jButton1;
private javax.swing.JButton jButton2;
private javax.swing.JComboBox<String> jComboBox1;
private javax.swing.JLabel jLabel1;
private javax.swing.JLabel jLabel2;
private javax.swing.JLabel jLabel3;
private javax.swing.JLabel jLabel4;
private javax.swing.JPanel jPanel1;
private javax.swing.JPasswordField jPasswordField1;
private javax.swing.JTextField jTextField1;   
}

At lines

con=Connections.getConnection();
pst=con.prepareStatement("select * from `login` where username=? and passwor=?");
pst.setString(1, unmae);

it is getting error.
It says that cannot find symbol variable Connections.
incompatible types:java.sql.PreparedStatement cannot be converted to com.mysql.jdbc.PreparedStatement

Please help me.

答案1

得分: 1

在您的导入中存在一个问题，您需要从 java.sql 而不是从 com.mysql.jdbc 导入 Connection、PreparedStatement 和 ResultSet，所以请使用：

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;

而不是：

import com.mysql.jdbc.Connection;
import com.mysql.jdbc.PreparedStatement;
英文:

There are a problem in your imports, you have to import Connection, PreparedStatement, and ResultSet from java.sql and not from com.mysql.jdbc, so use :

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;

instead of this:

import com.mysql.jdbc.Connection;
import com.mysql.jdbc.PreparedStatement;

答案2

得分: 1

在 Connections.getConnection() 的位置，应该使用 DriverManager 来初始化连接。

类似这样：

    conn = DriverManager.getConnection(
                   "jdbc:" + this.dbms + "://" +
                   this.serverName +
                   ":" + this.portNumber + "/",
                   connectionProps);

来源：https://docs.oracle.com/javase/tutorial/jdbc/basics/connecting.html#db_connection_url

英文:

in the place of Connections.getConnection(), should use DriverManager to initialize the connection.

Something like

    conn = DriverManager.getConnection(
"jdbc:" + this.dbms + "://" +
this.serverName +
":" + this.portNumber + "/",
connectionProps);

https://docs.oracle.com/javase/tutorial/jdbc/basics/connecting.html#db_connection_url

huangapple
  • 本文由 发表于 2020年10月20日 16:00:56
  • 转载请务必保留本文链接：https://go.coder-hub.com/64440898.html
  • java
  • mysql
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