入门

基本概念祥解各个对象1.DriverManager2.Connetion3.Statement4.ResultSet对象ResulSet使用 JDBCUtils简易

基本概念

其实是一套接口。每个数据库的厂商需要去实现这个接口，提供数据库jar包。

导入jar包 下载地址（https://dev.mysql.com/downloads/connector/j/）注册驱动获取数据库来凝结对象 Connection定义sql获取执行sql的对象Statement执行sql，获得结果处理结果释放资源 import java.sql.Connection; import java.sql.DriverManager; import java.sql.SQLException; import java.sql.Statement; public class JDBCdemo2 { public static void main(String[] args) { Statement stmt = null; Connection conn = null; try { //注册驱动 Class.forName("com.mysql.cj.jdbc.Driver"); //定义sql String sql = "insert into student values('cwm',29,99,null)"; //获取连接接对象 conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/mydb?serverTimezone=UTC","root","123456"); //获取执行对象 stmt = conn.createStatement(); //执行sql int count = stmt.executeUpdate(sql); //处理结果 System.out.println(count); } catch (Exception e) { e.printStackTrace(); }finally { //释放资源 if (stmt!=null){ try { stmt.close(); } catch (SQLException e) { e.printStackTrace(); } } if (conn!=null){ try { conn.close(); } catch (SQLException e) { e.printStackTrace(); } } } } }

祥解各个对象

1.DriverManager

功能： 注册驱动 ；Class.forName(“com.mysql.cj.jdbc.Driver”); 获取连接对象。

2.Connetion

获取执行sql的对象 Statement createStatemente() PreparedStatement PreparedStatement(String sql)管理事务 开启事务 setAutoCommit(boolean autoCommit):设置该参数为false 即开启事务 提交事务 commit() 回滚事务 rollback

3.Statement

用于执行静态sql并返回生成的结果的对象

执行sql int executeUpdate(String sql) : 执行DML(增删改）语句、DDL(create,alter,drop)语句,返回影响的行数。 ResultSet executeQuery(String sql): 执行select语句

4.ResultSet对象

封装执行结果集对象

boolean next():光标移到下一行 getInt(参数) getString(参数) 参数 Int：第n列 String ：列的名称

ResulSet使用

import domain.Stu; import java.sql.*; import java.util.ArrayList; import java.util.List; public class JDBCdemo4 { public List<Stu> findAll() { Statement stmt = null; Connection conn = null; ResultSet rs = null; String sql = "select * from student"; Stu stu = null; List<Stu> list = new ArrayList<>(); try { // 获取数据库来凝结对象 Connection conn = JDBCUtils.getConnetion(); //获取执行对象 stmt = conn.createStatement(); //执行sql rs = stmt.executeQuery(sql); //处理结果 while (rs.next()) { String name = rs.getString("name"); int age = rs.getInt("age"); double score = rs.getDouble("score"); int id = rs.getInt("id"); stu = new Stu(); stu.setAge(age); stu.setId(id); stu.setScore(score); stu.setName(name); list.add(stu); } return list; }catch (SQLException e) { e.printStackTrace(); } finally { //释放资源 if (rs != null) { try { rs.close(); } catch (SQLException e) { e.printStackTrace(); } } if (stmt != null) { try { stmt.close(); } catch (SQLException e) { e.printStackTrace(); } } if (conn != null) { try { conn.close(); } catch (SQLException e) { e.printStackTrace(); } } } return null; } public static void main(String[] args) { List<Stu> list = new JDBCdemo3().findAll(); System.out.println(list); } }

JDBCUtils简易

import java.io.FileReader; import java.io.IOException; import java.net.URL; import java.sql.*; import java.util.Properties; //工具类的方法一般是static public class JDBCUtils { private static String url; private static String user; private static String password; private static String driver; static { //读取资源文件，获取值 try { Properties po =new Properties(); ClassLoader classLoader = JDBCUtils.class.getClassLoader(); URL res = classLoader.getResource("jdbc.properties"); String path =res.getPath(); System.out.println(path); po.load(new FileReader("src/jdbc.properties")); url = po.getProperty("url"); user = po.getProperty("user"); password = po.getProperty("password"); driver = po.getProperty("driver"); Class.forName(driver); } catch (IOException e) { e.printStackTrace(); } catch (ClassNotFoundException e) { e.printStackTrace(); } } /* *获取来连接 *@return 连接对象 */ public static Connection getConnetion() throws SQLException { return DriverManager.getConnection(url,user,password); } public static void close(Statement stmt,Connection conn){ if (stmt != null) { try { stmt.close(); } catch (SQLException e) { e.printStackTrace(); } } if (conn != null) { try { conn.close(); } catch (SQLException e) { e.printStackTrace(); } } } public static void close(ResultSet rs,Statement stmt, Connection conn){ if (rs != null) { try { rs.close(); } catch (SQLException e) { e.printStackTrace(); } } if (stmt != null) { try { stmt.close(); } catch (SQLException e) { e.printStackTrace(); } } if (conn != null) { try { conn.close(); } catch (SQLException e) { e.printStackTrace(); } } } }

配置文件如下：

url=jdbc:mysql:///你的表?serverTimezone=UTC user=root password=你的密码 driver=com.mysql.cj.jdbc.Driver

未完待续。。。。