【JDBC】编程（2）-

import java.sql.*;

public class DBUtil {

    

    //静态代码块在类加载时执行，并且只执行一次
    static {
        try {
            Class.forName("com.mysql.cj.jdbc.Driver");
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        }
    }

    private DBUtil(){
    }

    
  
    //因为此方法是被调用的方法，所以出现异常直接上抛就行
    public static Connection getConnection () throws SQLException {
        return DriverManager.getConnection("jdbc:mysql://localhost:3306/bjpowernode"
                , "root", "888");
    }

    
  
    public static void close(Connection connection,Statement statement,ResultSet resultSet){
        if (resultSet != null) {
            try {
                resultSet.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
        if (statement != null) {
            try {
                statement.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }if (connection != null) {
            try {
                connection.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
    }
}

import java.sql.*;

public class JDBCTest03 {
    public static void main(String[] args) {
        Connection connection = null;
        PreparedStatement ps = null;
        ResultSet resultSet = null;

        try {
            //注册+获取连接
            connection = DBUtil.getConnection();

            //获取预编译的数据库操作对象
            String sql = "select loginPwd from t_user where loginPwd like ?";
            ps = connection.prepareStatement(sql);
            ps.setString(1,"_a%");

            //执行sql语句
            resultSet = ps.executeQuery();

            //处理查询结果集
            while (resultSet.next()){
                System.out.println(resultSet.getString("loginPwd"));
            }

        } catch (SQLException e) {
            e.printStackTrace();
        }finally {
            //关闭资源
            DBUtil.close(connection,ps,resultSet);
        }
    }
}

控制台输出结果：

aa000
8a8a88
6a

Process finished with exit code 0

总结：控制台输出结果正常，JDBC工具类 功能正常。