工具类JdbcUtils

Posted 2022-04-28 xiueer

/*
 * 
 * 这是一个工具类，一般工具类不能被继承，所以定义成final
 * 
 * 不需要构造实例，用私有的构造方法
 *  单例模式或者用static静态代码块，
 *  本例用static，没有实例
 * */
package cn.itcast.jdbc;

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

public final class JdbcUtils 

    private static String url = "jdbc:mysql://localhost:3306/jdbc";
    private static String user = "root";
    private static String password = "123456";

    private JdbcUtils() 
    

    // 注册驱动
    static 
        try 
            Class.forName("com.mysql.jdbc.Driver");
         catch (Exception e) 
            throw new ExceptionInInitializerError(e);
        
    

    //建立连接
    public static Connection getConnection() throws SQLException 
        return DriverManager.getConnection(url, user, password);
    

    //释放资源
    public static void free(ResultSet rs, Statement st, Connection conn) 
        try 
            if (rs != null)
                rs.close();
         catch (SQLException e) 
            e.printStackTrace();
         finally 
            try 
                if (st != null)
                    st.close();
             catch (SQLException e) 
                e.printStackTrace();
             finally 
                try 
                    if (conn != null)
                        conn.close();
                 catch (SQLException e) 
                    e.printStackTrace();