解决"java.lang.ClassNotFoundException: com.mysql.jdbc.Driver"

按照以前的老方法，写Java的主程序通过JDBC来连MySQL。

//1: import java.sql.*;
import java.sql.*;

public class JDBC_Driver {
    // JDBC driver name and database URL;
    static final String dbDriver = "com.mysql.jdbc.Driver";
    static final String DB_URL = "jdbc:mysql://localhost:3306/mysql";

    // database credentials
    static final String USER = "your username";
    static final String PWD = ""; // input your passoword

    public static void main(String[] args) {
        Connection conn = null;
        Statement stmt = null;
        ResultSet rs = null;
        try{
            //2. Register JDBC driver (not necessary any more)
            Class.forName("com.mysql.jdbc.Driver");

            //3. open a connection
            System.out.println("Connecting to database");
            conn = DriverManager.getConnection(DB_URL, USER, PWD);

            //4. create statement
            System.out.println("Creating statement");
            stmt = conn.createStatement();

            //5. execute query;
            String sql;
            sql = "select * from items";
            rs = stmt.executeQuery(sql);

            //6. extract data from result set
            while(rs.next()){
                //retrieve by column name
                int id = rs.getInt(1);
                String name = rs.getString(2);
                double price = rs.getDouble(3);

                // display values
                System.out.print("ID: " + id + " ");
                System.out.print("name: " + name + " ");
                System.out.print("price: " + price + " ");
                System.out.println();

            }
            rs.close();
            stmt.close();
            conn.close();
        }
        catch (Exception e) {
            System.out.println("Error: " + e);
        }

    }

}

报错了！老说是在"forClass"那儿错了。

解决办法是要引入JDBC的driver。上次做的project是用的Oracle，这次自己却粗心了。

所以按照“Java Web整合开发实战”P44的方法，在Eclipse里面用JDBC连接MySQL的数据库。下载了"connector/j"的jar文件，然后在项目里新建文件夹lib，把MySQL的JDBC driver拖拽进来。

随后又在整个项目的Java Build Path里面把driver作为作为internal jar导入。

另外一种方法，新建lib文件夹，直接在"Java Build Path"里面添加一个External Jar也可以达到同样的效果。

参考的视频: https://www.youtube.com/watch?v=oBeB2YqOCpU