JDBC操作步骤和JDBC事务
1、加载驱动
这是1.8版本包里面的，如果是1.5的话可以把cj除去
//加载驱动
Class.forName("com.mysql.cj.jdbc.Driver");2、获得连接
//2、打开连接
Connection connection = DriverManager.getConnection("jdbc:mysql://localhost:3306", "root", "123456");
3、编写sql
//3. 预处理sql语句
PreparedStatement preparedStatement = connection.prepareStatement("insert into hero(username,sex,age,type,price,aag) values(?,?,?,?,?,?)");
4、获得执行sql语句的对象
//4. 获得执行sql语句的对象
preparedStatement.setString(1,"金蝉");
preparedStatement.setString(2,"男");
preparedStatement.setString(3,"11");
preparedStatement.setString(4,"法师");
preparedStatement.setString(5,"18888");
preparedStatement.setString(6,"100");5、执行sql语句，并返回结果
//5. 执行sql语句，并返回结果
preparedStatement.execute();
//基于查询语句
ResultSet resultSet = preparedStatement.executeQuery();
6、处理结果
（这个是基于第五步的查询语句）
//6. 处理结果
while (resultSet.next()){
System.out.println(resultSet.getString(1));
}7、释放资源
//7. 释放资源
preparedStatement.close();
connection.close();jdbc事务
1.只要中途出现错乱都两边都要回滚回去，不会执行下一步
/**
* 模拟转账
* @param args
*/
public static void main(String[] args) {
Connection connection=null;
try {
//1、加载驱动
Class.forName("com.mysql.cj.jdbc.Driver");
//2、打开连接
connection = DriverManager.getConnection("jdbc:mysql://localhost:3306/game", "root", "123456");
//启动手动提交
connection.setAutoCommit(false);
//3、预处理mysql
PreparedStatement preparedStatement = connection.prepareStatement("update a set money = money - ? where id = ?");
preparedStatement.setDouble(1,500);
preparedStatement.setInt(2,1);
int num = preparedStatement.executeUpdate();
System.out.println(num);
System.out.println(1/0);
preparedStatement.setDouble(1,-500);
preparedStatement.setInt(2,2);
num = preparedStatement.executeUpdate();
System.out.println(num);
//提交事务
connection.commit();
} catch (Exception e) {
try {
//事务回滚
connection.rollback();
} catch (SQLException ex) {
ex.printStackTrace();
}
}
}1.数据库操作失败数据
1.数据库操作成功后的数据
JDBC示例：
要创建DBUtils工具类
package com.blb.day01;
import java.sql.*;
public class DBUtils {
static {
try {
Class.forName("com.mysql.cj.jdbc.Driver");
} catch (ClassNotFoundException e) {
e.printStackTrace();
}
}
/**
* 获取连接
* @return
* @throws ClassNotFoundException
* @throws SQLException
*/
public static Connection getConnection() throws ClassNotFoundException, SQLException {
return DriverManager.getConnection("jdbc:mysql://localhost:3306/game","root","123456");
}
/**
* 执行增删改查
* @param connection
* @param sql
* @param params
* @return
* @throws SQLException
*/
public static int executeUpdate(Connection connection, String sql, Object... params) throws SQLException {
return setParams(connection,sql,params).executeUpdate();
}
/**
* 设置参数
* @param connection
* @param sql
* @param params
* @return
*/
private static PreparedStatement setParams(Connection connection, String sql, Object[] params) throws SQLException {
PreparedStatement preparedStatement = connection.prepareStatement(sql);
for (int i = 0; i 测试类：
package com.blb.day01;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.time.LocalDate;
import java.time.LocalDateTime;
import java.time.format.DateTimeFormatter;
import java.util.Scanner;
public class Demo1 {
static Scanner scanner = new Scanner(System.in);
public static void main(String[] args) throws SQLException, ClassNotFoundException {
while (true){
String[] strings ="录入员工信息,删除员工信息,修改员工信息,员工打卡,查看全部员工打卡信息,查看指定员工全部打卡信息,查看指定员工指定日期打卡信息,退出".split(",");
for (int i = 0; i 0){
System.out.println("修改成功！");
}else {
System.out.println("修改失败！");
}
}
/**
* 员工打卡
*/
private static void getSignInfo() throws SQLException, ClassNotFoundException {
while (true){
System.out.println("请输入要打卡的员工编号：");
int num = scanner.nextInt();
ResultSet resultSet = DBUtils.executeQuery(DBUtils.getConnection(), "select * from emp where empno=?", num);
if (resultSet.next()){
String date = LocalDate.now().toString();
ResultSet resultSet1 = DBUtils.executeQuery(DBUtils.getConnection(), "select * from signinfo where empno=? and signdate = ?", num, date);
String datetime = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss").format(LocalDateTime.now());
if (resultSet1.next()){
DBUtils.executeUpdate(DBUtils.getConnection(),"update signinfo set signout = ? where empno = ?",datetime,num);
System.out.println("下班打卡成功！");
}else {
DBUtils.executeUpdate(DBUtils.getConnection(),"insert into signinfo(empno, signdate, signin) values (?,?,?)",num,LocalDate.now(),datetime);
System.out.println("上班打卡成功！");
}
break;
}else {
System.out.println("员工不存在！！");
}
}
}
/**
* 删除
*/
private static void delEmp() throws SQLException, ClassNotFoundException {
System.out.println("请输入要删除的员工编号：");
int num = scanner.nextInt();
int i = DBUtils.executeUpdate(DBUtils.getConnection(), "delete from emp where empno=?", num);
if (i>0){
System.out.println("删除失败");
}else {
System.out.println("删除成功！");
}
}
/**
* 新增
*/
private static void addEmp() throws SQLException, ClassNotFoundException {
System.out.println("请输入要添加员工姓名：");
String name = scanner.next();
DBUtils.executeUpdate(DBUtils.getConnection(),"insert into emp(ename) values(?)",name);
System.out.println("增加成功！");
}
}