package cn.itcast.jdbc;import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;import org.junit.Test;import cn.itcast.utils.JdbcUtils;//jdbc的crud操作
public class JdbcDemo6 {@Testpublic void findByIdTest(){//1.定义sqlString sql = "select * from user where id= 1";Connection con = null;Statement st = null;ResultSet rs = null;try {//1.注册驱动  Class.forName("com.mysql.jdbc.Driver");//2.获取连接try {con = DriverManager.getConnection("jdbc:mysql:///day17", "root", "");//3.获取操作sql语句对象Statementst =   con.createStatement();//4.执行sqlrs = st.executeQuery(sql);//5.遍历结果集while(rs.next()){int id = rs.getInt("id");//String id = rs.getString("id");//虽然用getString()行,但是用getInt()比较合适String username = rs.getString("username");String password = rs.getString("password");String email = rs.getString("email");System.out.println(id+"   "+username+"   "+password+"   "+email);}} catch (SQLException e) {// TODO Auto-generated catch blocke.printStackTrace();}} catch (ClassNotFoundException e) {// TODO Auto-generated catch blocke.printStackTrace();}finally{//6.释放资源try {if(rs !=null ){rs.close();}} catch (SQLException e) {// TODO Auto-generated catch blocke.printStackTrace();}try {if(st!=null){st.close();}} catch (SQLException e) {// TODO Auto-generated catch blocke.printStackTrace();}try {if(con!=null){con.close();}} catch (SQLException e) {// TODO Auto-generated catch blocke.printStackTrace();}   }
}//添加操作@Testpublic void addTest(){//定义sqlString sql = "insert into user values(null,'张三','123','zs@163.com')";Connection con = null;Statement st = null;ResultSet rs = null;try {//1.注册驱动  Class.forName("com.mysql.jdbc.Driver");//2.获取连接try {con = DriverManager.getConnection("jdbc:mysql:///day17", "root", "");//3.获取操作sql语句对象Statementst =   con.createStatement();//4.执行sqlint row = st.executeUpdate(sql);System.out.println(row);if(row!=0){System.out.println("添加成功");}} catch (SQLException e) {// TODO Auto-generated catch blocke.printStackTrace();}} catch (ClassNotFoundException e) {// TODO Auto-generated catch blocke.printStackTrace();}finally{//6.释放资源try {if(rs !=null ){rs.close();}} catch (SQLException e) {// TODO Auto-generated catch blocke.printStackTrace();}try {if(st!=null){st.close();}} catch (SQLException e) {// TODO Auto-generated catch blocke.printStackTrace();}try {if(con!=null){con.close();}} catch (SQLException e) {// TODO Auto-generated catch blocke.printStackTrace();}   }}//update操作@Testpublic void updateTest(){//将id=3的人的password修改为456String password = "456";String sql = "update user set password='"+password+"' where id=3";//1.得到ConnectionConnection con = null;Statement st = null;try {con = JdbcUtils.getConnectin();//3.获取操作sql语句对象Statementst =   con.createStatement();//4.执行sqlint row = st.executeUpdate(sql);System.out.println(row);if(row!=0){System.out.println("添加成功");}} catch (ClassNotFoundException e) {// TODO Auto-generated catch blocke.printStackTrace();} catch (SQLException e) {// TODO Auto-generated catch blocke.printStackTrace();}finally{//关闭资源try {if(st!=null){st.close();}} catch (SQLException e) {// TODO Auto-generated catch blocke.printStackTrace();}try {if(con!=null){con.close();}} catch (SQLException e) {// TODO Auto-generated catch blocke.printStackTrace();}  }}
}

package cn.itcast.utils;import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;public class JdbcUtils {public static Connection getConnectin() throws ClassNotFoundException, SQLException{Class.forName("com.mysql.jdbc.Driver");//在开发中用哪个Statement人家有选择的权利,你不能给它抽取//2.获取连接Connection       con = DriverManager.getConnection("jdbc:mysql:///day17", "root", "");return con;
}
}