将数据库从 MySQL 更改为 SQLite 后的 Java 项目错误

Question

我正在学习Java 我已经使用 mysql 创建了简单的 (CRUD) java 程序，它工作正常

我想尝试使用相同的数据库切换到 SQLite(我已经将 mysql 数据库转换为 sqlite)

我正在使用这个 JDBC 驱动程序:https://bitbucket.org/xerial/sqlite-jdbc

但不知何故，netbeans无法完成运行我的程序(尽管之前没有错误) 我在输出栏上收到许多新错误:

java.lang.ClassNotFoundException: org.sqlite.JDBCException in thread "AWT-EventQueue-0" java.lang.NullPointerException
at tes.MainForm.Tampil(MainForm.java:46)
at tes.MainForm.<init>(MainForm.java:85)
at tes.MainForm$4.run(MainForm.java:329)
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)`

我的 DBConnection 类

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
public class DBConnection {   
Connection c = null;
Statement script;

public DBConnection(){
    try{
        Class.forName("org.sqlite.JDBC");
 //  Class.forName("com.mysql.jdbc.Driver");
   // c = DriverManager.getConnection("jdbc:ucanaccess://c:/asa.accdb");
 c = DriverManager.getConnection("jdbc:sqlite:C:/titit2.db");
   // c = DriverManager.getConnection("jdbc:mysql://localhost:3306/titit","root","root");
    script = c.createStatement(ResultSet.TYPE_SCROLL_INSENSITIVE, ResultSet.CONCUR_UPDATABLE);
    System.out.println("Koneksi Sukses");
    }catch(  SQLException | ClassNotFoundException ex){
    System.err.print(ex);
    }
}
}

在我的 mainform 类中(第 23-46 行)

    private void Tampil(){
    try{
        int row = tabel.getRowCount();
        for(int i=0;i<row;i++){
            tabeldata.delete(0, row);
        }
        String sql;
        sql = "SELECT * from asu";
            ResultSet rs = c.script.executeQuery(sql);

        while(rs.next()){
            DataPegawai d = new DataPegawai();
            d.setNo(rs.getInt("no"));
            d.setNip(rs.getInt("nip"));
            d.setNama(rs.getString("nama"));
            d.setDivisi(rs.getString("divisi"));
            d.setLevel(rs.getInt("level"));
            tabeldata.add(d);
        }
    }catch(SQLException e){
        System.err.print(e);
    }
}

Answer 1

ClassNotFoundException 是您可以在运行时获得的异常。请参阅:http://docs.oracle.com/javase/7/docs/api/java/lang/ClassNotFoundException.html它说可能的原因:

Thrown when an application tries to load in a class through its string name using:

• The forName method in class Class.
• The findSystemClass method in class ClassLoader .
• The loadClass method in class ClassLoader.

所以从我的角度来看，问题是您没有在 netbeans 中正确地将它添加到类路径中。

此外，您应该检查您使用的是稳定版本的驱动程序。我建议使用:sqlite-jdbc-3.7.2.jar