Java Netbeans 登录表单

Netbeans Login form

提问by

I am having a problem with login form in java it seems there is nothing wrong with the connection to the database but still when i clicked the login button nothing is happening my guess is there is something missing or error in my code but i can seem to find it I hope you guys help me Thanks in advance :)

我在 Java 中遇到登录表单的问题，似乎与数据库的连接没有任何问题，但是当我单击登录按钮时仍然没有发生任何事情我猜是我的代码中缺少某些内容或错误，但我似乎可以找到它我希望你们帮助我在此先感谢:)

package splash_screen;


import java.sql.*;
import javax.swing.*;


public class Loginform extends javax.swing.JFrame {
Connection conn=null;
ResultSet rs=null;
PreparedStatement pst=null;
public Loginform() {
    initComponents();
    conn=Connect.connectDB();
}


@SuppressWarnings("unchecked")
// <editor-fold defaultstate="collapsed" desc="Generated     Code">                          
private void initComponents() {

    jTextField1 = new javax.swing.JTextField();
    jLabel1 = new javax.swing.JLabel();
    jLabel2 = new javax.swing.JLabel();
    jButton1 = new javax.swing.JButton();
    jPasswordField1 = new javax.swing.JPasswordField();

    setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);

    jLabel1.setText("Username:");

    jLabel2.setText("Password:");

    jButton1.setText("Login");
    jButton1.addActionListener(new java.awt.event.ActionListener() {
        public void actionPerformed(java.awt.event.ActionEvent evt) {
            jButton1ActionPerformed(evt);
        }
    });

    javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane());
    getContentPane().setLayout(layout);
    layout.setHorizontalGroup(
        layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
        .addGroup(layout.createSequentialGroup()
            .addContainerGap()
                 .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                .addGroup(layout.createSequentialGroup()
                    .addComponent(jLabel1)
                    .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
                    .addComponent(jTextField1, javax.swing.GroupLayout.PREFERRED_SIZE, 137, javax.swing.GroupLayout.PREFERRED_SIZE))
                .addGroup(layout.createSequentialGroup()
                    .addComponent(jLabel2)
                    .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
                    .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                        .addComponent(jButton1)
                        .addComponent(jPasswordField1, javax.swing.GroupLayout.PREFERRED_SIZE, 139, javax.swing.GroupLayout.PREFERRED_SIZE))))
            .addContainerGap(197, Short.MAX_VALUE))
    );
    layout.setVerticalGroup(
        layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
        .addGroup(layout.createSequentialGroup()
            .addContainerGap()
            .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                .addComponent(jLabel1)
                .addComponent(jTextField1, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE))
            .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.UNRELATED)
            .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                .addComponent(jLabel2)
                .addComponent(jPasswordField1, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE))
            .addGap(18, 18, 18)
            .addComponent(jButton1)
            .addContainerGap(197, Short.MAX_VALUE))
    );

    pack();
}// </editor-fold>                        

private void jButton1ActionPerformed(java.awt.event.ActionEvent evt)         {                                         
    String sql="Select * from Account where username=? and password=?";

        try{
            pst=conn.prepareStatement(sql);
            pst.setString(1,jTextField1.getText());
            pst.setString(2,jPasswordField1.getText());

            rs=pst.executeQuery(sql);

            if(rs.next()){
                JOptionPane.showMessageDialog(null,"Password and Username is correct");
                Home a=new Home();
            a.setVisible(true);

            }
            else{
               JOptionPane.showMessageDialog(null,"Password and Username is incorrect"); 
            }

        }
        catch(SQLException e){

        }
}                                        

/**
 * @param args the command line arguments
 */
public static void main(String args[]) {
    /* Set the Nimbus look and feel */
    //<editor-fold defaultstate="collapsed" desc=" Look and feel setting code (optional) ">
    /* If Nimbus (introduced in Java SE 6) is not available, stay with the default look and feel.
     * For details see http://download.oracle.com/javase/tutorial/uiswing/lookandfeel/plaf.html 
     */
    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(Loginform.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
    } catch (InstantiationException ex) {
        java.util.logging.Logger.getLogger(Loginform.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
    } catch (IllegalAccessException ex) {
        java.util.logging.Logger.getLogger(Loginform.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
    } catch (javax.swing.UnsupportedLookAndFeelException ex) {
        java.util.logging.Logger.getLogger(Loginform.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
    }
    //</editor-fold>

    /* Create and display the form */
    java.awt.EventQueue.invokeLater(new Runnable() {
        public void run() {
            new Loginform().setVisible(true);
        }
    });
}

回答by JB Nizet

Replace

代替

rs.executeQuery(sql);

by

经过

rs.executeQuery();

The SQL string has already been passed to the statement at construction time.

SQL 字符串已在构造时传递给语句。