Question

好吧，所以我在数据库上工作，其中登录的唯一标准是密码。数据库只能在离线状态下从一台计算机运行州（本地）我读了一遍，它指出了我在创建嵌入式数据库的方向。 我相信我正在使用Java 在Netbeans中使用derby。

我的表包含一个主键作为帐号，名称和密码。

我正在尝试：将输入的密码与数据库中的表（用户）中的“密码”列进行比较，因此表=各种用户信息+密码列

我的问题：当我尝试访问数据库以将输入的密码（在passwordField中）与数据库密码进行比较时，会抛出一些错误。

错误

Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
at MainApplication.Login.loginButtMouseClicked(Login.java:112)
at MainApplication.Login.access$000(Login.java:7)
at MainApplication.Login$1.mouseClicked(Login.java:37)
at java.awt.AWTEventMulticaster.mouseClicked(AWTEventMulticaster.java:270)
at java.awt.Component.processMouseEvent(Component.java:6528)
at javax.swing.JComponent.processMouseEvent(JComponent.java:3324)
at java.awt.Component.processEvent(Component.java:6290)
at java.awt.Container.processEvent(Container.java:2234)
at java.awt.Component.dispatchEventImpl(Component.java:4881)
at java.awt.Container.dispatchEventImpl(Container.java:2292)
at java.awt.Component.dispatchEvent(Component.java:4703)
at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4898)
at java.awt.LightweightDispatcher.processMouseEvent(Container.java:4542)
at java.awt.LightweightDispatcher.dispatchEvent(Container.java:4462)
at java.awt.Container.dispatchEventImpl(Container.java:2278)
at java.awt.Window.dispatchEventImpl(Window.java:2750)
at java.awt.Component.dispatchEvent(Component.java:4703)
at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:758)
at java.awt.EventQueue.access$500(EventQueue.java:97)
at java.awt.EventQueue$3.run(EventQueue.java:709)
at java.awt.EventQueue$3.run(EventQueue.java:703)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:75)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:86)
at java.awt.EventQueue$4.run(EventQueue.java:731)
at java.awt.EventQueue$4.run(EventQueue.java:729)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:75)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:728)
at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:201)
at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:116)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:105)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:101)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:93)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:82)

这是我的连接助手类

package MainApplication;

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

public class DBConnect {

    public static Connection Connect() {
        Connection conn;

        try {
        String host = "jdbc:derby://localhost:1527/USERS";
        String uName = "test";
        String uPass = "test";
        conn = DriverManager.getConnection(host, uName, uPass);
        JOptionPane.showMessageDialog(null, "Database Connected");
        return conn;
        }

        catch (SQLException err){
            JOptionPane.showMessageDialog(null ,err);
            return null;
        }

    }
}

这是我没有摆动组件的登录基本代码

package MainApplication;

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

public class Login extends javax.swing.JFrame {
    Connection conn;
    PreparedStatement stmt;
    ResultSet rs;

//Initializer
    public Login() {
        initComponents();
        DBConnect.Connect();
    }

登录按钮

    private void loginButtMouseClicked(java.awt.event.MouseEvent evt) {                                       
    String pass = passText.getText();
    try {
        stmt = (PreparedStatement) conn.createStatement();
        String SQL = "select * from users where password  ='" + pass + "'";
        rs = stmt.executeQuery(SQL);
        if (rs.next()){
            int id = rs.getInt("ACCOUNTNUMBER");
            String firstName = rs.getString("firstName");
            String lastName = rs.getString("lastName");
            String accInfo = id + " " + firstName + ", " + lastName;
            System.out.println(accInfo);
        }    
    }
    catch (SQLException e) {
            JOptionPane.showMessageDialog(null, e);
    }
}

旁注：我读过散列或盐析对安全性来说可能是一个好主意......但我可能必须能够在实现之前连接？还听说使用准备好的声明更加安全，这就是为什么那里。

感谢您的时间:)

嵌入式数据库登录系统（netbeans java）

0 个答案: