Java Netbeans 数据库连接错误

Question

我是 Netbeans 的新手。我正在尝试通过 Netbeans 和 mysql 工作台创建一个关于商店管理的新项目作为我的数据库。但是我在连接数据库时遇到了问题。这里给出了我的代码：

    enter code here
package MyDb.utils;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
import java.util.logging.Level;
import java.util.logging.Logger;



public class DbConnection {
     private static Connection conn=null;
    static{
        Throwable e = null;
        try {
            Class.forName("com.mysql.jdbc.Driver");
            try {
                System.out.println("Connecting Database!!");
                conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/GanpatiDB","root","");
                System.out.println("");
            } catch (SQLException ex) {
                throw new RuntimeException("Cannot connect the database!", e);
            }
        } catch (ClassNotFoundException ex) {
            Logger.getLogger(DbConnection.class.getName()).log(Level.SEVERE, null, e);
            System.out.println("Terminating application...check database");
            System.exit(0);
        }
         finally {
    System.out.println("Closing the connection.");

}
    }
    private static Object connection;


public DbConnection(){

    }
    public static Connection getConnection(){
        return conn;
    }
    public static void closeConnection() throws Exception{

        conn.close();
    }


}

调试项目后，控制台给出的结果为

构建成功（总时间：0 秒） 但它仍然显示一些错误如下：

    Jan 14, 2014 1:47:13 PM MyDb.utils.DbConnection <clinit>
Terminating application...check database
SEVERE: null
com.mysql.jdbc.exceptions.jdbc4.MySQLSyntaxErrorException: Access denied for user ''@'localhost' to database 'GanpatiDB[root on Default schema]'
    at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
    at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:57)
    at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
    at java.lang.reflect.Constructor.newInstance(Constructor.java:526)
    at com.mysql.jdbc.Util.handleNewInstance(Util.java:409)
    at com.mysql.jdbc.Util.getInstance(Util.java:384)
    at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:1054)
    at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:3566)
    at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:3498)
    at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:919)
    at com.mysql.jdbc.MysqlIO.secureAuth411(MysqlIO.java:4004)
    at com.mysql.jdbc.MysqlIO.doHandshake(MysqlIO.java:1284)
    at com.mysql.jdbc.ConnectionImpl.connectOneTryOnly(ConnectionImpl.java:2312)
    at com.mysql.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:2122)
    at com.mysql.jdbc.ConnectionImpl.<init>(ConnectionImpl.java:774)
    at com.mysql.jdbc.JDBC4Connection.<init>(JDBC4Connection.java:49)
    at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
    at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:57)
    at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
    at java.lang.reflect.Constructor.newInstance(Constructor.java:526)
    at com.mysql.jdbc.Util.handleNewInstance(Util.java:409)
    at com.mysql.jdbc.ConnectionImpl.getInstance(ConnectionImpl.java:375)
    at com.mysql.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:289)
    at java.sql.DriverManager.getConnection(DriverManager.java:571)
    at java.sql.DriverManager.getConnection(DriverManager.java:233)
    at MyDb.utils.DbConnection.<clinit>(DbConnection.java:20)
    at desktopapplication1.NewJFrame.<init>(NewJFrame.java:27)
    at desktopapplication1.NewJFrame$2.run(NewJFrame.java:199)
    at java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:251)
    at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:733)
    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.awt.EventQueue.dispatchEvent(EventQueue.java:703)
    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

构建显示为成功是有充分理由的：您正在捕捉实际错误并自己编写日志语句：

catch (ClassNotFoundException ex) {
Logger.getLogger(DbConnection.class.getName()).log(Level.SEVERE, null, e);
System.out.println("Terminating application...check database");
System.exit(0);
}

因为它正在捕获错误，所以代码按预期执行（如果您希望它显示为失败，您应该将 System.exit 的参数更改为 -1）。

您遇到的错误是ClassNotFoundException，Java 似乎无法使用Class.forName("com.mysql.jdbc.Driver"); 找到您尝试查找的 MySQL 驱动程序。如果你看日志，根本没有提到驱动程序，这似乎支持了这个理论。