Question

java.lang.ClassNotFoundException：org.apache.derby.jdbc.ClientDriver

at java.net.URLClassLoader$1.run(URLClassLoader.java:372)

at java.net.URLClassLoader$1.run(URLClassLoader.java:361)

at java.security.AccessController.doPrivileged(Native Method)

at java.net.URLClassLoader.findClass(URLClassLoader.java:360)

at java.lang.ClassLoader.loadClass(ClassLoader.java:424)

at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:308)

at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
at java.lang.Class.forName0(Native Method)
at java.lang.Class.forName(Class.java:259)
at iir.connection.main(connection.java:35)

2014年11月29日下午5:03:01 iir.connection main

SEVERE：null

java.sql.SQLException：没有为jdbc找到合适的驱动程序：derby：// localhost：1527 / bala

at java.sql.DriverManager.getConnection(DriverManager.java:689)

at java.sql.DriverManager.getConnection(DriverManager.java:270)

at iir.connection.main(connection.java:40)

线程“main”中的异常java.lang.NullPointerException

at iir.connection.main(connection.java:44)

Answer 1

由于您尚未共享代码，因此很难理解您的要求。不过，我正在分享一些示例代码，可以帮助您排除故障：

使用的数据库：Derby

要安装和配置数据库，请参阅链接：https://db.apache.org/derby/papers/DerbyTut/install_software.html#derby_configure

定义属性文件：Database.properties

url=jdbc:derby:myDerbyDB
driver=org.apache.derby.jdbc.EmbeddedDriver

如果需要修改数据库，这将帮助您轻松修改代码。

测试与数据库的连接：Connect.java

package com.stackoverflow.test.Derby;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
import java.util.ResourceBundle;

public class Connect 
{
    public static Connection con;
    static String url,driver;

    public static void connectMe() throws ClassNotFoundException, SQLException
    {
        ResourceBundle resource = ResourceBundle.getBundle("database");
        driver=resource.getString("driver");
        url=resource.getString("url");
        Class.forName(driver);

        con = DriverManager.getConnection(url);
        if(con!=null)
            System.out.println("Connection Established!");
    }
}

创建表格：TableCreation.java

package com.stackoverflow.test.Derby;

import java.sql.SQLException;
import java.sql.Statement;

public class TableCreation 
{
    public static void main(String args[]) throws ClassNotFoundException, SQLException
    {
        Connect.connectMe();
        Statement st = Connect.con.createStatement();
        String query = "CREATE TABLE myJavaTable  (ID INT NOT NULL GENERATED ALWAYS AS IDENTITY CONSTRAINT ID_PK PRIMARY KEY, DATA VARCHAR(20) NOT NULL) ";
        boolean val = st.execute(query);
        if (val == false) {
        System.out.println("Creation Successfull!");
        } else {
            System.out.println("Creation not successfull!");
        }
        Connect.con.close();
     }

}

将数据插入表格：PreparedStatementInsert.java

package com.stackoverflow.test.Derby;

import java.sql.PreparedStatement;
import java.sql.SQLException;
import java.sql.Statement;
import java.io.*;

public class PreparedStatementInsert 
{
    public static void main(String args[]) throws ClassNotFoundException, SQLException, IOException
    {
        Connect.connectMe();
        String query;
        Statement st = Connect.con.createStatement();
        BufferedReader in = new BufferedReader(new InputStreamReader(System.in));


        query="Insert into myJavaTable(DATA) Values(?)";
        PreparedStatement ps = Connect.con.prepareStatement(query);

        System.out.print("Enter the number of records to be inserted: ");
        int n = Integer.parseInt(in.readLine());
        for(int i = 1; i<=n; i++)
        {
            System.out.print("Enter the Data: ");
            ps.setString(1, in.readLine());
            ps.executeUpdate();
            System.out.println("One record inserted!");
        }
        TableRetrieve.main(args);
        Connect.con.close();
    }

}

显示表格内容：TableRetrieve.java

package com.stackoverflow.test.Derby;

import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;

public class TableRetrieve 
{
    public static void main(String args[]) throws ClassNotFoundException, SQLException
    {
        Connect.connectMe();
        Statement st = Connect.con.createStatement();
        ResultSet rSet = st.executeQuery("Select * from myJavaTable");

        while(rSet.next())
        {
            System.out.print("ID: "+rSet.getString(1));
            System.out.println("\tName: "+rSet.getString(2));
        }
        Connect.con.close();
    }

}

更新表格的内容：TableUpdate.java

package com.stackoverflow.test.Derby;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;

public class TableUpdate 
{
    public static void main(String args[]) throws ClassNotFoundException, SQLException, IOException
    {
        Connect.connectMe();
        String query;
        boolean flag = false;
        Statement st = Connect.con.createStatement();
        BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
        System.out.println("Enter the ID of the record to be updated");
        int userID = Integer.parseInt(in.readLine());

        query = "Select * from myJavaTable";
        ResultSet rSet = st.executeQuery(query);

        while(rSet.next())
        {
            int id = rSet.getInt("ID");
            if(userID==id)
            {
                System.out.print("Enter the new data: ");
                String str = in.readLine();
                query="Update myJavaTable set Data='"+str+"' where ID="+id;
                int exe = st.executeUpdate(query);
                flag = true;
                break;
            }
        }

        if(flag==true)
            System.out.println("Updation successfull!");
        else
            System.out.println("Record not found!");

        System.out.println("Table after updation is as follows:");
        TableRetrieve.main(args);
        Connect.con.close();
    }

}

删除创建的表：TableDrop.java

package com.stackoverflow.test.Derby;

import java.sql.SQLException;
import java.sql.Statement;

public class TableDrop
{
    public static void main(String args[]) throws ClassNotFoundException, SQLException
    {
        Connect.connectMe();
        Statement st = Connect.con.createStatement();
        String query = "Drop table myJavaTable";
        boolean val = st.execute(query);
        if(val==false) {
        System.out.println("Table Dropped!");
        } else {
            System.out.println("Table cannot be dropped!");
        }
        Connect.con.close();
    }

}

希望这些可以帮到你。如果您需要更多信息，请评论答案。如果您能为此做出贡献，请更新我的答案，以便对其他人更有用。

创建数据库连接时出错？

1 个答案: