java - Java：无法加载 EmbeddedDerby 的 JDBC 驱动程序

Question

为 EmbeddedDerby 加载 JDBC 驱动程序时出现问题。以下是我编译和运行程序的案例

• 情况1：

  编译：E:\java\WorkReminder>javac -d class source/MyDerbyProgram.java

  运行：E:\java\WorkReminder>java -cp class MyDerbyProgram

  错误：

  无法加载 JDBC 驱动程序 org.apache.derby.jdbc.EmbeddedDriver 请检查您的 CLASSPATH。java.lang.ClassNotFoundException: org.apache.derby.jdbc.EmbeddedDriver at java.net.URLClassLoader$1.run(URLClassLoader.java:200) at java.security.AccessController.doPrivileged(Native Method) at java.net.URLClassLoader。 findClass(URLClassLoader.java:188) at java.lang.ClassLoader.loadClass(ClassLoader.java:306) at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:268) at java.lang.ClassLoader.loadClass(ClassLoader .java:251) 在 java.lang.ClassLoader.loadClassInternal(ClassLoader.java:319) 在 java.lang.Class.forName0(Native Method) 在 java.lang.Class.forName(Class.java:164) 在 MyDerbyProgram。 loadDriver(MyDerbyProgram.java:143) 在 MyDerbyProgram.go(MyDerbyProgram.

• 案例2：如果我这样做，一切都好

  编译：E:\java\WorkReminder>javac -d class source/MyDerbyProgram.java

  更改目录：E:\java\WorkReminder>cd class

  运行：E:\java\WorkReminder\class>java MyDerbyProgram

  输出：

  加载适当的驱动程序

  插入的行。

  2-----

  1956_ _ __ _ __ _ +__ _ __ _ __ _ ___ _河内

  1975_ _ __ _ __ _ _ +__ _ __ _ __ _ ___ _西贡

  SimpleApp 完成

有人可以帮我解释为什么我在案例 1 中出现错误，因为我正在编写一个更复杂的程序吗？我的代码：

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.ArrayList;
import java.util.Properties;

public class MyDerbyProgram
{
    /* the default framework is embedded*/
    private String framework = "embedded";
    private String driver = "org.apache.derby.jdbc.EmbeddedDriver";
    private String protocol = "jdbc:derby:";

    public static void main(String[] args)
    {
        new MyDerbyProgram().go(args);
        System.out.println("SimpleApp finished");
    }

    void go(String[] args)
    {
        /* load the desired JDBC driver */
        loadDriver();
        try
        {
            Connection connection = DriverManager.getConnection(protocol + "testDB; create=true");
            connection.setAutoCommit(false);


            //Create table
            Statement statement = connection.createStatement(ResultSet.TYPE_SCROLL_INSENSITIVE, ResultSet.CONCUR_UPDATABLE);
            statement.execute("create table location(num int, address varchar(40))");

            //Insert
            PreparedStatement psInsertStatement = connection.prepareStatement("insert into location values(?, ?)");
            psInsertStatement.setInt(1, 1956);
            psInsertStatement.setString(2, "Ha Noi");
            psInsertStatement.executeUpdate();
            psInsertStatement.setInt(1, 1975);
            psInsertStatement.setString(2, "Sai Gon");
            psInsertStatement.executeUpdate();
            System.out.println("Row inserted.");

            //Select
            ResultSet resultSet = statement.executeQuery("select * from location");

            int totalRows = 0;

            resultSet.last();
            totalRows = resultSet.getRow();
            resultSet.beforeFirst();
            System.out.println(totalRows + "-----");

            String strPrintResult = "";
            while(resultSet.next())
            {
                strPrintResult += resultSet.getString("num") + "___________________+_________________________" + resultSet.getString("address") + "\n";
            }           
            System.out.println(strPrintResult);

            //Drop table
            statement.execute("drop table location");

            //Commit transaction
            connection.commit();

            //Close
            statement.close();
            statement = null;

            psInsertStatement.close();
            psInsertStatement = null;

            resultSet.close();
            resultSet = null;

            connection.close();
            connection = null;
        }

        catch(SQLException se)
        {
            System.out.println(se.toString());
        }
    }

    private void loadDriver() {
    try {
        Class.forName(driver).newInstance();
        System.out.println("Loaded the appropriate driver");
    } catch (ClassNotFoundException cnfe) {
        System.err.println("\nUnable to load the JDBC driver " + driver);
        System.err.println("Please check your CLASSPATH.");
        cnfe.printStackTrace(System.err);
    } catch (InstantiationException ie) {
        System.err.println(
                    "\nUnable to instantiate the JDBC driver " + driver);
        ie.printStackTrace(System.err);
    } catch (IllegalAccessException iae) {
        System.err.println(
                    "\nNot allowed to access the JDBC driver " + driver);
        iae.printStackTrace(System.err);
    }
    }
    private void parseArguments(String[] args)
    {
        if (args.length > 0) {
            if (args[0].equalsIgnoreCase("derbyclient"))
            {
                framework = "derbyclient";
                driver = "org.apache.derby.jdbc.ClientDriver";
                protocol = "jdbc:derby://localhost:1527/";
            }
        }
    }
}

问候

Answer 1

该-cp选项设置类路径，你不需要这个

看这里