MySql数据库连接问题-ClassNotFoundException [英] MySql Database Connection Issues - ClassNotFoundException

问题描述

我正在尝试获取用户信息，然后将其显示在Swing中的表上。目前，每次执行下面的代码时，我都会收到以下错误消息。

I am attempting to fetch User Information, and then display it onto a Table in Swing. Currently I am getting an error as follows each time I execute the piece of code below.

java.lang.ClassNotFoundException: com.mysql.jdbc.Driver
at java.net.URLClassLoader$1.run(Unknown Source)
at java.net.URLClassLoader$1.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
at java.lang.Class.forName0(Native Method)
at java.lang.Class.forName(Unknown Source)
at me.sage.hopkins.gui.and.mysql.Test.initialize(Test.java:53)
at me.sage.hopkins.gui.and.mysql.Test.<init>(Test.java:41)
at me.sage.hopkins.gui.and.mysql.Test$1.run(Test.java:28)
at java.awt.event.InvocationEvent.dispatch(Unknown Source)
at java.awt.EventQueue.dispatchEventImpl(Unknown Source)
at java.awt.EventQueue.access$400(Unknown Source)
at java.awt.EventQueue$3.run(Unknown Source)
at java.awt.EventQueue$3.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(Unknown Source)
at java.awt.EventQueue.dispatchEvent(Unknown Source)
at java.awt.EventDispatchThread.pumpOneEventForFilters(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForFilter(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.run(Unknown Source)

代码

Code

public class Test {

private JFrame frame;
private JTable table;

/**
 * Launch the application.
 */
public static void main(String[] args) {
    EventQueue.invokeLater(new Runnable() {
        public void run() {
            try {
                Test window = new Test();
                window.frame.setVisible(true);
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
    });
}

/**
 * Create the application.
 */
public Test() {
    initialize();
}

/**
 * Initialize the contents of the frame.
 */
private void initialize() {
    frame = new JFrame();
    frame.setBounds(100, 100, 450, 300);
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

    try{
        Class.forName("com.mysql.jdbc.Driver");
    //*Mysql Configurations*\\
    Connection connect = DriverManager.getConnection("jdbc:mysql://204.44.86.142/League_Stats","root","password");
    PreparedStatement sql = connect.prepareStatement("SELECT * FROM `Champion Data`");
    ResultSet rs = sql.executeQuery();
    rs.next();
    String ChampionName = rs.getString("Champion");
    String UserName = rs.getString("User Name");

    String[] columnNames = {"Username", "Champion"};
    Object[]data = {UserName, ChampionName};
    //*Draw Table*\\
    table = new JTable((Object[][]) data, columnNames);
    GridBagConstraints gbc_table = new GridBagConstraints();
    gbc_table.insets = new Insets(0, 0, 0, 5);
    gbc_table.fill = GridBagConstraints.BOTH;
    gbc_table.gridx = 2;
    gbc_table.gridy = 6;
    frame.getContentPane().add(table, gbc_table);


    }catch(Exception e){
        e.printStackTrace();
    }
}
}

新错误

这是引入JDBC库后收到的新错误。

This is the new error I recieved after introducing the JDBC Library.

java.lang.ClassCastException: [Ljava.lang.Object; cannot be cast to [[Ljava.lang.Object;
at me.sage.hopkins.gui.and.mysql.Test.initialize(Test.java:65)
at me.sage.hopkins.gui.and.mysql.Test.<init>(Test.java:41)
at me.sage.hopkins.gui.and.mysql.Test$1.run(Test.java:28)
at java.awt.event.InvocationEvent.dispatch(Unknown Source)
at java.awt.EventQueue.dispatchEventImpl(Unknown Source)
at java.awt.EventQueue.access$400(Unknown Source)
at java.awt.EventQueue$3.run(Unknown Source)
at java.awt.EventQueue$3.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(Unknown Source)
at java.awt.EventQueue.dispatchEvent(Unknown Source)
at java.awt.EventDispatchThread.pumpOneEventForFilters(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForFilter(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.run(Unknown Source)

推荐答案

下载jdbc驱动程序。为此，您可以使用此链接

Download the jdbc driver. For that you can use this link

然后在月食中

1. 右键单击您的项目


2. 点击属性


3. 选择Java构建路径


4. 选择库


5. 按添加外部jar


6. 选择已下载的jar文件


7. 单击确定
   
   

1. Right click your project
2. click on properties
3. Select java build path
4. Select libraries
5. press add external jars
6. select the jar file you have downloaded
7. click ok
   

这可能会解决您的问题。

This might fix your problem.

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