package cn.itcast.demo2;import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;import org.junit.Test;public class Demo2 {/** 连接数据库，得到Connection就算成功！* 对数据库做增、删、改*/@Testpublic void fun1() throws ClassNotFoundException, SQLException {/** 一、得到Connection* 1. 准备四大参数* 2. 加载驱动类* 3. 得到Connection*/// 准备四大参数String driverClassName = "com.mysql.jdbc.Driver";// jdbc协议的格式！jdbc:工商的名称:子协议（由工商自己来规定）// 对mysql而言，它的子协议结构：//主机:端口号/数据库名称String url = "jdbc:mysql://localhost:3306/mydb3";String username = "root";String password = "123";// 加载驱动类
        Class.forName(driverClassName);// 使用DriverManager，以及省下的3个参数，得到ConnectionConnection con = DriverManager.getConnection(url, username, password);/** 二、对数据库做增、删、改* 1. 通过Connection对象创建Statement* > Statement语句的发送器，它的功能就是向数据库发送sql语句！* 2. 调用它的int executeUpdate(String sql)，它可以发送DML、DDL*/// 1. 通过Connection得到Statement对象Statement stmt = con.createStatement();// 2. 使用Statement发送sql语句！
//        String sql = "INSERT INTO stu VALUES('ITCAST_0003', 'wangWu', 88, 'male')";
//        String sql = "UPDATE stu SET name='zhaoLiu', age=22, " +
//                "gender='female' WHERE number='ITCAST_0003'";String sql = "DELETE FROM stu";int r = stmt.executeUpdate(sql);System.out.println(r);}/*** 执行查询* @throws ClassNotFoundException * @throws SQLException */@Testpublic void fun2() throws ClassNotFoundException, SQLException {/** 一、得到Connection* 二、得到Statement，发送select语句* 三、对查询返回的“表格”进行解析！*//** 一、得到连接* 1. 准备四大连接参数*/String driverClassName = "com.mysql.jdbc.Driver";String url = "jdbc:mysql://localhost:3306/exam";String username = "root";String password = "123";/** 2. 加载驱动类*/Class.forName(driverClassName);/** 3. 通过省下的三个参数调用DriverManger的getConnection()，得到连接*/Connection con = DriverManager.getConnection(url, username, password);/** 二、得到Statement，执行select语句* 1. 得到Statement对象：Connection的createStatement()方法*/Statement stmt = con.createStatement();/** 2. 调用Statement的ResultSet rs = executeQuery(String querySql)*/ResultSet rs = stmt.executeQuery("select * from emp");/** 三、解析ResultSet* 1. 把行光标移动到第一行，可以调用next()方法完成！*/while(rs.next()) {//把光标向下移动一行，并判断下一行是否存在！int empno = rs.getInt(1);//通过列编号来获取该列的值！String ename = rs.getString("ename");//通过列名称来获取该列的值double sal = rs.getDouble("sal");System.out.println(empno +  ", " + ename + ", " + sal);}/** 四、关闭资源* 倒关*/rs.close();stmt.close();con.close();//这个东东，必须要关，不关就死！
    }// 规范化
    @Testpublic void fun3() throws Exception {Connection con = null;//定义引用Statement stmt = null;ResultSet rs = null;try {/** 一、得到连接*/String driverClassName = "com.mysql.jdbc.Driver";String url = "jdbc:mysql://localhost:3306/exam";String username = "root";String password = "123";Class.forName(driverClassName);con = DriverManager.getConnection(url, username, password);//实例化/** 二、创建Statement*/stmt = con.createStatement();String sql = "select * from emp";rs = stmt.executeQuery(sql);rs.last();//把光标移动到最后一行
System.out.println(rs.getRow());rs.beforeFirst();/** 三、循环遍历rs，打印其中数据* * getString()和getObject()是通用的！*/
//            while(rs.next()) {
//                System.out.println(rs.getObject(1) + ", "
//                        + rs.getString("ename") + ", " + rs.getDouble("sal"));
//            }int count = rs.getMetaData().getColumnCount();while(rs.next()) {//遍历行for(int i = 1; i <= count; i++) {//遍历列
                    System.out.print(rs.getString(i));if(i < count) {System.out.print(", ");}}System.out.println();}} catch(Exception e) {throw new RuntimeException(e);} finally {// 关闭if(rs != null) rs.close();if(stmt != null) stmt.close();if(con != null) con.close();}}
}