我写了一个所谓的'错误少'代码但我在使用应用程序时遇到了一些问题。 这是我的代码：
import java.sql.*;
import java.util.ArrayList;
import java.util.List;
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
public class Login implements ActionListener {
Connection conn1 = null;
Statement stmt1 = null;
Connection conn2 = null;
Statement stmt2 = null;
Connection conn3 = null;
Statement stmt3 = null;
JFrame frame = new JFrame("Login Window");
JPanel startPanel = new JPanel();
JPanel adminPanel = new JPanel();
JPanel engineerPanel = new JPanel();
JButton adminLogin = new JButton("Admin Login");
JButton engineerLogin = new JButton("Engineer Login");
JTextField adminUsername = new JTextField();
JPasswordField adminPassword = new JPasswordField();
JButton adminLog = new JButton("Login");
JButton adminBack = new JButton("Go Back");
JComboBox engineerUsername = new JComboBox();
JPasswordField engineerPassword = new JPasswordField();
JButton engineerLog = new JButton("Login");
JButton engineerBack = new JButton("Go Back");
public Login(){
//Establishing connection with database
conn1 = sqliteConnection.dbConnector();
frame.setLayout(new GridLayout(1, 1));
/*
Setting up the startPanel
*/
startPanel.setLayout(new GridLayout(3, 3, 15, 15));
// Row 1
startPanel.add(new JLabel(" "));
JLabel loginType = new JLabel(" SELECT LOGIN TYPE");
loginType.setFont(new Font("Tahoma", Font.BOLD, 12));
startPanel.add(loginType);
startPanel.add(new JLabel(" "));
// Row 2
startPanel.add(new JLabel(" "));
startPanel.add(adminLogin);
startPanel.add(new JLabel(" "));
// Row 3
startPanel.add(new JLabel(" "));
startPanel.add(engineerLogin);
startPanel.add(new JLabel(" "));
adminLogin.addActionListener(this);
engineerLogin.addActionListener(this);
/*
Setting up adminPanel
*/
adminPanel.setLayout(new GridLayout(4, 2, 15, 15));
// Row 1
adminPanel.add(new JLabel("Admin Login"));
adminPanel.add(new JLabel(" "));
// Row 2
adminPanel.add(new JLabel("Username"));
adminPanel.add(adminUsername);
// Row 3
adminPanel.add(new JLabel("Password"));
adminPanel.add(adminPassword);
// Row 4
adminPanel.add(adminLog);
adminPanel.add(adminBack);
adminLog.addActionListener(this);
adminBack.addActionListener(this);
//Initial Visibility False
adminPanel.setVisible(false);
/*
Setting up engineerPanel
*/
engineerPanel.setLayout(new GridLayout(4, 2, 15, 15));
// Row 1
engineerPanel.add(new JLabel("Engineer Login"));
engineerPanel.add(new JLabel(" "));
// Row 2
try{
Class.forName("org.sqlite.JDBC");
conn1.setAutoCommit(false);
stmt1 = conn1.createStatement();
ResultSet rs1 = stmt1.executeQuery( "SELECT * FROM EngineerData;" );
List<String> engineerNamesList = new ArrayList<String>();
while ( rs1.next() ){
String name = rs1.getString("Name");
engineerNamesList.add(name);
}
// Converting array list to array
String[] engineerNames = new String[engineerNamesList.size()];
engineerNamesList.toArray(engineerNames);
// Adding array into combo-box
for (String en : engineerNames){
engineerUsername.addItem(en);
}
rs1.close();
stmt1.close();
conn1.close();
}
catch ( Exception e1 ) {
JOptionPane.showMessageDialog(null, e1);
}
engineerPanel.add(new JLabel("Engineer Name"));
engineerPanel.add(engineerUsername);
// Row 3
engineerPanel.add(new JLabel("Password"));
engineerPanel.add(engineerPassword);
// Row 4
engineerPanel.add(engineerLog);
engineerPanel.add(engineerBack);
engineerLog.addActionListener(this);
engineerBack.addActionListener(this);
//Initial Visibility False
engineerPanel.setVisible(false);
frame.setSize(500, 200);
frame.setResizable(false);
frame.add(startPanel);
frame.setVisible(true);
}
//Method to convert integar array list to integar array
public int[] convertIntegers(List<Integer> integers)
{
int[] ret = new int[integers.size()];
for (int i=0; i < ret.length; i++)
{
ret[i] = integers.get(i).intValue();
}
return ret;
}
//Admin login method
public void adminLogin(){
String adminUser = adminUsername.getText();
String adminPass = adminPassword.getText();
String adminUserDB = null;
String adminPassDB = null;
conn2 = sqliteConnection.dbConnector();
try{
Class.forName("org.sqlite.JDBC");
conn2.setAutoCommit(false);
stmt2 = conn2.createStatement();
ResultSet rs2 = stmt2.executeQuery( "SELECT * FROM AdminData;" );
adminUserDB = rs2.getString("Username");
adminPassDB = rs2.getString("Password");
conn2.close();
stmt2.close();
rs2.close();
}
catch (Exception e2){
}
if (adminUser.equals(adminUserDB) && adminPass.equals(adminPassDB)){
AdminClass ac = new AdminClass();
frame.dispose();
}
else if (adminUser.equals(adminUserDB) && adminPass != adminPassDB){
JOptionPane.showMessageDialog(null, "Incorrect Password.\nPlease enter again.");
}
else if (adminUser != adminUserDB && adminPass.equals(adminPassDB)){
JOptionPane.showMessageDialog(null, "Incorrect Username.\nPlease enter again.");
}
else if (adminUser != adminUserDB && adminPass != adminPassDB){
JOptionPane.showMessageDialog(null, "Incorrect Username and Password.\nPlease enter again.");
}
}
//Engineer login method
public void engineerLogin(){
String engineerUser = engineerUsername.getSelectedItem().toString();
String engineerPass = engineerPassword.getText();
List<String> engineerNamesList = new ArrayList<String>();
List<String> engineerPasswordsList = new ArrayList<String>();
ArrayList<Integer> uniqueIDList = new ArrayList<Integer>();
conn3 = sqliteConnection.dbConnector();
try{
Class.forName("org.sqlite.JDBC");
conn3.setAutoCommit(false);
stmt3 = conn3.createStatement();
ResultSet rs3 = stmt3.executeQuery( "SELECT * FROM EngineerData;" );
while ( rs3.next() ){
int uniqueId = rs3.getInt("UniqueId");
String engineerUserDB = rs3.getString("Name");
String engineerPassDB = rs3.getString("Password");
//Adding data from database to variables that exist in our code
engineerNamesList.add(engineerUserDB);
engineerPasswordsList.add(engineerPassDB);
uniqueIDList.add(uniqueId);
}
conn3.close();
stmt3.close();
rs3.close();
}
catch (Exception e3){
}
// Creating usable arrays from array lists
String[] engineerNames = new String[engineerNamesList.size()];
engineerNamesList.toArray(engineerNames);
String[] engineerPasswords = new String[engineerPasswordsList.size()];
engineerPasswordsList.toArray(engineerPasswords);
int[] uniqueIDs = convertIntegers(uniqueIDList);
for (int i = 0; i < engineerNames.length; i++){
boolean condition = (engineerUser.equals(engineerNames[i]) && engineerPass.equals(engineerPasswords[i]));
if (condition){
frame.dispose();
EngineerPanel ep = new EngineerPanel();
//This ID is the identifier of the engineer
//This will be used to generate data only for his particular project
ep.setUniqueID(uniqueIDs[i]);
break;
}
else if (i>= 1 && condition != true){
JOptionPane.showMessageDialog(null, "Incorrect Password");
continue;
}
}
}
public void actionPerformed(ActionEvent e){
if (e.getSource() == adminLogin){
startPanel.setVisible(false);
frame.remove(startPanel);
frame.add(adminPanel);
adminPanel.setVisible(true);
}
if (e.getSource() == engineerLogin){
startPanel.setVisible(false);
frame.remove(startPanel);
frame.add(engineerPanel);
engineerPanel.setVisible(true);
}
if (e.getSource() == adminBack){
adminUsername.setText(null);
adminPassword.setText(null);
adminPanel.setVisible(false);
frame.remove(adminPanel);
frame.add(startPanel);
startPanel.setVisible(true);
}
if (e.getSource() == engineerBack){
engineerPassword.setText(null);
engineerPanel.setVisible(false);
frame.remove(engineerPanel);
frame.add(startPanel);
startPanel.setVisible(true);
}
if (e.getSource() == adminLog){
adminLogin();
}
if (e.getSource() == engineerLog){
engineerLogin();
}
}
}
所以在这里你可以看到我正在使用sqlite数据库。工程师的授权仅适用于第一位工程师，但现在适用于所有工程师。即使数据正确，也表明用户数据不正确。即使我一直点击确定，JOptionPane仍然会弹出。几次点击后，它只是用于下一个JFrame，虽然它说密码不正确。 请帮忙！
答案 0 :(得分：0)
如果我理解你的问题，你的逻辑是有缺陷的。你这样做：
Uncaught TypeError: Cannot set property 'innerHTML' of null
因此，一旦发现输入的信息与数据库行不匹配，就会显示错误。所以第一个对象的一切都很好，因为第一行会匹配。但对于第二个对象，它将显示错误，因为您已输入第二行的数据，并且第一行将不匹配。然后你“继续”，所以你永远不会到达第二个数据库行。 你的逻辑应该是：
for (int i = 0; i < engineerNames.length; i++){
boolean condition = ...
if (condition){
// OK
} else {
// show error
}
}
boolean ok=false;
for (int i = 0; i < engineerNames.length; i++){
boolean condition = ...
ok |= condition;
}
if (ok){
// OK
} else {
// show error
}
是一个OR运算符：您想查看是否有任何行匹配。当然，如果确实如此，你可以继续避免查看其他比赛。
但是为什么不使用提供的名称和密码的查询呢？
ok |= condition看看你是否得到任何结果。