1 Class.forName()加载驱动

2 DriverManager获取Connect连接

3 创建Statement执行SQL语句

4 返回ResultSet查询结果

5释放资源

package cn.tree.dao;import java.sql.Connection;import java.sql.DriverManager;import java.sql.ResultSet;import java.sql.SQLException;import java.sql.Statement;public class MenuDao {	// 查询主目录	public void getMainList() {		Connection connection = null;		Statement st = null;		ResultSet rs = null;		try {			// 1、加载驱动			Class.forName("com.mysql.jdbc.Driver");			// 2、获取数据库连接			connection = DriverManager.getConnection(					"jdbc:mysql://127.0.0.1:3306/tree", "root", "123321");			// 3、获取Statement对象，执行sql语句			String sql = "select * from main";			st = connection.createStatement();			rs = st.executeQuery(sql);			// 4、处理sql执行结果			while (rs.next()) {				int id = rs.getInt("id");				String name = rs.getString("name");				System.out.println("id: " + id + "\t" + "name: " + name);			}		} catch (ClassNotFoundException e) {			e.printStackTrace();		} catch (SQLException e) {			e.printStackTrace();		} finally {			try {				// 5、释放资源				rs.close();				st.close();				connection.close();			} catch (SQLException e) {				e.printStackTrace();			}		}	}	public static void main(String[] args) {		MenuDao menuDao = new MenuDao();		menuDao.getMainList();	}}