Java 为什么rs.next()不能正常工作?
编辑:解决了!谢谢你们D 即使使用正确的凭据键入,仍会出现错误showMessageDialog。。 我相信rs.next()将返回一个大于0的值,然后它必须确认用户的凭据是否与users_表中的凭据匹配,但我始终 获取错误消息,就好像凭据不匹配一样Java 为什么rs.next()不能正常工作?,java,mysql,oop,Java,Mysql,Oop,编辑:解决了!谢谢你们D 即使使用正确的凭据键入,仍会出现错误showMessageDialog。。 我相信rs.next()将返回一个大于0的值,然后它必须确认用户的凭据是否与users_表中的凭据匹配,但我始终 获取错误消息,就好像凭据不匹配一样 import java.sql.*; import javax.swing.*; public class System extends javax.swing.JFrame { // variables needed for db c
import java.sql.*;
import javax.swing.*;
public class System extends javax.swing.JFrame {
// variables needed for db connection
Connection conn;
Statement stmt;
ResultSet rs;
String sql;
String user;
char[] pass;
//for table row count
int ctr = 0;
//temporary variables needed in retrieving and inserting records in our db
int user_id;
String username;
String password;
public System() {
initComponents();
setLocationRelativeTo(null);
dbConnect();
}
public void dbConnect() {
conn = null;
String url = "jdbc:mysql://localhost:3306/item_db";
String driver = "com.mysql.jdbc.Driver";
String userName = "root";
String password = "";
try {
Class.forName(driver).newInstance();
conn = DriverManager.getConnection(url, userName, password);
stmt = conn.createStatement(ResultSet.TYPE_SCROLL_INSENSITIVE, ResultSet.CONCUR_UPDATABLE);
sql = "Select * from users_table";
rs = stmt.executeQuery(sql);//rs - will hold the records from the databa sql = "Select * from item_table";se
} catch (Exception e) {
JOptionPane.showMessageDialog(this, e.getMessage());
}
}
private void login() {
try {
if (user != null && pass != null) {
sql = "Select * from users_table Where username='" + user + "' and password='" + pass + "'";
rs = stmt.executeQuery(sql);
rs.next();
if ((user.equals(username)) && (pass.equals(password))) {
JOptionPane.showMessageDialog(null, "You are now logon!");
}
else {
JOptionPane.showMessageDialog(null, "damn!", "alert", JOptionPane.ERROR_MESSAGE);
}
}
} catch (SQLException err) {
JOptionPane.showMessageDialog(this, err.getMessage());
}
}
@SuppressWarnings("unchecked")
// <editor-fold defaultstate="collapsed" desc="Generated Code">
private void initComponents() {
jLabel1 = new javax.swing.JLabel();
jLabel2 = new javax.swing.JLabel();
jTextField1 = new javax.swing.JTextField();
jButton1 = new javax.swing.JButton();
jButton2 = new javax.swing.JButton();
jPasswordField1 = new javax.swing.JPasswordField();
jLabel3 = new javax.swing.JLabel();
setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);
jLabel1.setFont(new java.awt.Font("Calibri", 0, 18)); // NOI18N
jLabel1.setText("Username:");
jLabel2.setFont(new java.awt.Font("Calibri", 0, 18)); // NOI18N
jLabel2.setText("Password:");
jButton1.setText("Login");
jButton1.addActionListener(new java.awt.event.ActionListener() {
public void actionPerformed(java.awt.event.ActionEvent evt) {
jButton1ActionPerformed(evt);
}
});
jButton2.setText("Cancel");
jLabel3.setIcon(new javax.swing.ImageIcon(getClass().getResource("/login.png"))); // NOI18N
javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane());
getContentPane().setLayout(layout);
layout.setHorizontalGroup(
layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGroup(layout.createSequentialGroup()
.addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGroup(layout.createSequentialGroup()
.addGap(46, 46, 46)
.addComponent(jLabel3))
.addGroup(layout.createSequentialGroup()
.addGap(82, 82, 82)
.addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGroup(layout.createSequentialGroup()
.addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.TRAILING)
.addComponent(jLabel2)
.addComponent(jLabel1))
.addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
.addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING, false)
.addComponent(jTextField1)
.addComponent(jPasswordField1, javax.swing.GroupLayout.PREFERRED_SIZE, 134, javax.swing.GroupLayout.PREFERRED_SIZE)))
.addGroup(layout.createSequentialGroup()
.addGap(51, 51, 51)
.addComponent(jButton1)
.addGap(28, 28, 28)
.addComponent(jButton2)))))
.addContainerGap(52, Short.MAX_VALUE))
);
layout.setVerticalGroup(
layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGroup(javax.swing.GroupLayout.Alignment.TRAILING, layout.createSequentialGroup()
.addComponent(jLabel3, javax.swing.GroupLayout.DEFAULT_SIZE, 100, Short.MAX_VALUE)
.addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
.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.RELATED)
.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)
.addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
.addComponent(jButton1)
.addComponent(jButton2))
.addGap(29, 29, 29))
);
pack();
}// </editor-fold>
private void jButton1ActionPerformed(java.awt.event.ActionEvent evt) {
// TODO add your handling code here:
//str = JOptionPane.showInputDialog(this, "Enter id number: ");
user = jTextField1.getText();
pass = jPasswordField1.getPassword();
login();
}
/**
* @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(System.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
} catch (InstantiationException ex) {
java.util.logging.Logger.getLogger(System.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
} catch (IllegalAccessException ex) {
java.util.logging.Logger.getLogger(System.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
} catch (javax.swing.UnsupportedLookAndFeelException ex) {
java.util.logging.Logger.getLogger(System.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 System().setVisible(true);
}
});
}
// Variables declaration - do not modify
private javax.swing.JButton jButton1;
private javax.swing.JButton jButton2;
private javax.swing.JLabel jLabel1;
private javax.swing.JLabel jLabel2;
private javax.swing.JLabel jLabel3;
private javax.swing.JPasswordField jPasswordField1;
private javax.swing.JTextField jTextField1;
// End of variables declaration
}
import java.sql.*;
导入javax.swing.*;
公共类系统扩展了javax.swing.JFrame{
//数据库连接所需的变量
连接接头;
报表stmt;
结果集rs;
字符串sql;
字符串用户;
字符[]通过;
//用于表行计数
int ctr=0;
//在数据库中检索和插入记录时需要临时变量
int用户标识;
字符串用户名;
字符串密码;
公共系统(){
初始化组件();
setLocationRelativeTo(空);
dbConnect();
}
公共void dbConnect(){
conn=null;
String url=“jdbc:mysql://localhost:3306/item_db";
String driver=“com.mysql.jdbc.driver”;
字符串userName=“root”;
字符串密码=”;
试一试{
Class.forName(driver.newInstance();
conn=DriverManager.getConnection(url、用户名、密码);
stmt=conn.createStatement(ResultSet.TYPE\u SCROLL\u不敏感,ResultSet.CONCUR\u可更新);
sql=“从用户表中选择*”;
rs=stmt.executeQuery(sql);//rs-将保存数据库中的记录a sql=“Select*from item_table”se
}捕获(例外e){
showMessageDialog(这个,例如getMessage());
}
}
私有void登录(){
试一试{
if(user!=null&&pass!=null){
sql=“从users_表中选择*,其中username='“+user+”,password='“+pass+”;
rs=stmt.executeQuery(sql);
rs.next();
if((user.equals(username))&&(pass.equals(password))){
showMessageDialog(null,“您现在正在登录!”);
}
否则{
showMessageDialog(null,“该死!”,“警报”,JOptionPane.ERROR\u消息);
}
}
}捕获(SQLException错误){
showMessageDialog(this,err.getMessage());
}
}
@抑制警告(“未选中”)
//
私有组件(){
jLabel1=newjavax.swing.JLabel();
jLabel2=newjavax.swing.JLabel();
jTextField1=newjavax.swing.JTextField();
jButton1=newjavax.swing.JButton();
jButton2=newjavax.swing.JButton();
jPasswordField1=newjavax.swing.JPasswordField();
jLabel3=newjavax.swing.JLabel();
setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);
jLabel1.setFont(新的java.awt.Font(“Calibri”,0,18));//NOI18N
jLabel1.setText(“用户名:”);
setFont(新的java.awt.Font(“Calibri”,0,18));//NOI18N
jLabel2.setText(“密码:”);
jButton1.setText(“登录”);
jButton1.addActionListener(新java.awt.event.ActionListener(){
public void actionPerformed(java.awt.event.ActionEvent evt){
jButton1ActionPerformed(evt);
}
});
jButton2.setText(“取消”);
jLabel3.setIcon(新的javax.swing.ImageIcon(getClass().getResource(“/login.png”);//NOI18N
javax.swing.GroupLayout=newjavax.swing.GroupLayout(getContentPane());
getContentPane().setLayout(布局);
layout.setHorizontalGroup(
createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGroup(layout.createSequentialGroup()
.addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGroup(layout.createSequentialGroup()
.addGap(46,46,46)
.addComponent(jLabel3))
.addGroup(layout.createSequentialGroup()
.addGap(82,82,82)
.addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGroup(layout.createSequentialGroup()
.addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.training)
.addComponent(jLabel2)
.addComponent(jLabel1))
.addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
.addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING,false)
.addComponent(jTextField1)
.addComponent(jPasswordField1,javax.swing.GroupLayout.PREFERRED_SIZE,134,javax.swing.GroupLayout.PREFERRED_SIZE)))
.addGroup(layout.createSequentialGroup()
.addGap(51,51,51)
.addComponent(jButton1)
.addGap(28,28,28)
.addComponent(jButton2(()()))
.addContainerGap(52,简称最大值))
);
layout.setVerticalGroup(
createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGroup(javax.swing.GroupLayout.Alignment.TRAILING,layout.createSequentialGroup()
.addComponent(jLabel3,javax.swing.GroupLayout.DEFAULT\u SIZE,100,Short.MAX\u值)
.addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
.addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
.addComponent(jLabel1)
.addComponent(jTextField1,javax.swing.GroupLayout.PREFERRE
if (rs.next()) {
JOptionPane.showMessageDialog(null, "You are now logon!");
} else {
JOptionPane.showMessageDialog(null, "damn!", "alert", JOptionPane.ERROR_MESSAGE);
}
rs.next();
if ((user.equals(rs.getString("username"))) && (pass.equals(rs.getString("password")))) {
JOptionPane.showMessageDialog(null, "You are now logon!");
}
String username;
String password;
if ((user.equals(username)) && (pass.equals(password))) {
this.username = rs.getString("username");
this.password = rs.getString("password");
if (rs.next()) {