java - 登录表单 java mysql 在 netbeans 上失败

Question

我使用mysql制作了一个简单的java登录表单，安装了所有驱动程序等，并且我使用了另一个j2e项目中的连接代码，该代码有效，但登录不会在这里传递我的代码和错误日志，管理测试工作正常

private void jButton1ActionPerformed(java.awt.event.ActionEvent evt) {                                         
    String login = user.getText();
    String pass  = password.getText();

    if(login.equals("admin")&&pass.equals("admin")) {
        JOptionPane.showMessageDialog(null,"hi admin ");
    } else {
        try {
            Class.forName("sun.jdbc.odbc.JdbcOdbcDriver");
            System.out.println("driver MySQL JDBC charged");
        } catch (ClassNotFoundException e) {
            /*e.printStackTrace();*/
            System.out.println("Error charging driver");
        }
    }

    try {
        DriverManager.getConnection("jdbc:odbc:bd");

        rs = st.executeQuery("select * from users where nom='" + login + "' and passwd='" + pass+ "' ");

        if(rs.next())
            JOptionPane.showMessageDialog(null,"correct login ");
        else
            JOptionPane.showMessageDialog(null, "incorect login");
    } catch (SQLException e) {
        System.out.println("Error etablishing connexion");
    }              
}                                        

错误:

Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
    at javaapplication1.NewJFrame.jButton1ActionPerformed(NewJFrame.java:141)
    at javaapplication1.NewJFrame.access$000(NewJFrame.java:18)
    at javaapplication1.NewJFrame$1.actionPerformed(NewJFrame.java:49)
    at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:2018)
    at javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2341)
    at javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:402)
    at javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:259)
    at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(BasicButtonListener.java:252)
    at java.awt.Component.processMouseEvent(Component.java:6505)
    at javax.swing.JComponent.processMouseEvent(JComponent.java:3320)
    at java.awt.Component.processEvent(Component.java:6270)
    at java.awt.Container.processEvent(Container.java:2229)
    at java.awt.Component.dispatchEventImpl(Component.java:4861)
    at java.awt.Container.dispatchEventImpl(Container.java:2287)
    at java.awt.Component.dispatchEvent(Component.java:4687)
    at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4832)
    at java.awt.LightweightDispatcher.processMouseEvent(Container.java:4492)
    at java.awt.LightweightDispatcher.dispatchEvent(Container.java:4422)
    at java.awt.Container.dispatchEventImpl(Container.java:2273)
    at java.awt.Window.dispatchEventImpl(Window.java:2719)
    at java.awt.Component.dispatchEvent(Component.java:4687)
    at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:735)
    at java.awt.EventQueue.access$200(EventQueue.java:103)
    at java.awt.EventQueue$3.run(EventQueue.java:694)
    at java.awt.EventQueue$3.run(EventQueue.java:692)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76)
    at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:87)
    at java.awt.EventQueue$4.run(EventQueue.java:708)
    at java.awt.EventQueue$4.run(EventQueue.java:706)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76)
    at java.awt.EventQueue.dispatchEvent(EventQueue.java:705)
    at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:242)
    at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:161)
    at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:150)
    at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:146)
    at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:138)
    at java.awt.EventDispatchThread.run(EventDispatchThread.java:91)

Answer 1

您的连接出错..

DriverManager.getConnection("jdbc:odbc:bd");
    rs = st.executeQuery("select * from users where nom='" + login + "' and passwd='" + pass + "' ");

rs 结果集未定义 语句未定义 连接也未正确存储..

检查这个..

 Class.forName("com.mysql.jdbc.Driver");
    Connection conn = null;
    conn = DriverManager.getConnection("jdbc:mysql://hostname:port/dbname","username", "password");
System.out.println("-------- MySQL JDBC Connection Testing ------------");

try {
    Class.forName("com.mysql.jdbc.Driver");
} catch (ClassNotFoundException e) {
    System.out.println("Where is your MySQL JDBC Driver?");
    e.printStackTrace();
    return;
}

System.out.println("MySQL JDBC Driver Registered!");
Connection connection = null;

try {
    connection = DriverManager
    .getConnection("jdbc:mysql://localhost:3306/mkyongcom","root", "password");

} catch (SQLException e) {
    System.out.println("Connection Failed! Check output console");
    e.printStackTrace();
    return;
}

if (connection != null) {
    System.out.println("You made it, take control your database now!");
} else {
    System.out.println("Failed to make connection!");
}

}