JDBC demo

package com.zhangbz.jdbc;

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

public class JDBCDemo1 {

	public static void main(String[] args) {
		Connection conn = null;  //局部变量没有默认的初始化，类的成员变量才有
		Statement stat = null;
		ResultSet rs = null;

		try {
			//1.注册数据库驱动
			//--由于mysql在Driver类的实现中自己注册了一次，而我们又注册了一次，于是会导致mysql驱动被注册两次
			//--创建mysqldeDriver对象时，导致了程序和具体的mysql驱动绑死在了一起，在切换数据库时需要修改代码
			//DriverManager.registerDriver(new Driver());
			//反射
			Class.forName("com.mysql.jdbc.Driver");
			conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/day10", "root", "root");
			stat = conn.createStatement();
			rs = stat.executeQuery("select * from user");
			//5.遍历结果集获取查询对象
			while(rs.next()){
				String name = rs.getString("name");
				System.out.println(name);
			}
		} catch(Exception e) {
			e.printStackTrace();
		} finally {
			//6.关闭资源//异常处理
			if (rs != null) {
				try {
					rs.close();
				} catch (SQLException e) {
					// TODO Auto-generated catch block
					e.printStackTrace();
				} finally {
					rs = null;
				}
			}
			if (rs != null) {
				try {
					stat.close();
				} catch (SQLException e) {
					// TODO Auto-generated catch block
					e.printStackTrace();
				} finally {
					rs = null;
				}
			}
			if (rs != null) {
				try {
					conn.close();
				} catch (SQLException e) {
					// TODO Auto-generated catch block
					e.printStackTrace();
				} finally {
					rs = null;
				}
			}
		}
	}
}